10 Kidneys and Ureters

Technique Computed Tomography

Conventional Radiography The introduction of multislice helical CT has and Urography had a major impact on uroradiology. Multislice CT allows imaging during specific contrast Indications for intravenous (IV) pyelography opacification phases. Depending on the study (the term IV urography is used by some) have indication, the CT protocol used can be decreased considerably, but this examination modified accordingly. Thus suspected acute is still indicated if pyelocalyceal visualization urinary obstruction by a stone is studied is needed. Small transitional cell carcino- without contrast, in the workup of hypertension mas, pyeloureteritis cystica, medullary sponge and suspected renal artery stenosis emphasis is kidney, and papillary necrosis continue to be on arterial phase images, while some infections best identified with IV urography. A current are detected only during later phases; small major indication for IV urography is in investi- renal tumors are readily imaged in a breath- gating hematuria in adults, although here com- hold; potential living renal donor evaluation puted tomographic urography combined with is simplified and therapy aided by three- cystoscopy are making inroads, and magnetic dimensional (3D) imaging. Using a two-bolus resonance (MR) is not far behind. technique both a nephrogenic and excretory Intravenous urography is insensitive in phases can be obtained with one scan, although detecting small renal parenchymal tumors. such a protocol tends not to visualize all of the Thus about one third of tumors <3cm in diam- ureters completely. eter are not detected. Even with larger tumors Are screening serum creatinine levels neces- urography is generally insensitive in differenti- sary prior to contrast CT studies? Only 3% of ating benign from malignant tumors. This test, over 2000 consecutive outpatients undergoing however, does provide information on renal contrast-enhanced CT had elevated serum cre- function and gross anatomy, and it aids in eval- atinine levels, and risk factors were identified in uating disorders of the collective systems. It a majority of these (1); screening for risk factors tends to be somewhat inferior in infants com- appears adequate in this patient population. pared to older children. Renal opacification can be divided into Retrograde ureteropyelography has a role if three phases: first is an early vascular or bolus insufficient contrast is excreted during an IV phase, then a nephrogram phase (consisting urogram. For suspected obstruction, however, of a nephrogram), followed by a pyelogram currently noncontrast computed tomography or equilibrium (delayed) phase. A cortico- (CT) is considered to be superior. medullary phase, providing maximum differen-

571 572

ADVANCED IMAGING OF THE ABDOMEN tiation between renal cortex and medulla, and in planning a partial nephrectomy, such as occurs during the early phase. Whether a corti- orientation of blood vessels to a tumor or other comedullary phase or a later nephrogram phase structure. One should not rely only on 3D should be used for subtle tumor detection is images, however, because to an experienced eye debatable,although some evidence suggests that axial and coronal images provide more detailed the nephrogram phase is superior. Both neo- information, especially about small vessels that plasms and normal renal parenchyma enhance tend to be overlooked on 3D images. significantly more during the nephrogram In a patient with microscopic hematuria phase than during the corticomedullary phase. and a normal excretory urogram, should CT In general, more tumors <3cm in diameter are or ultrasonography (US) be performed next? detected on the nephrogram phase than on the Although this topic generated considerable corticomedullary phase. The onset of a nephro- controversy in the 1990s, currently many inves- gram phase varies among patients and tech- tigators believe that CT detects more tumors nique used; a faster injection rate results in an overall, especially smaller ones. In fact, a more earlier onset—roughly 100 seconds at 2mL/sec pertinent current question is whether CT or MR and 90 seconds at 3mL/sec. The cortico- is indicated as a primary imaging modality in medullary phase is more useful, however, for such a clinical setting. detection of such conditions as an aneurysm, arteriovenous malformation, or fistula, and in evaluating tumor vascularity. Also, the earlier Ultrasonography phase is more advantageous if optimal liver Renal cortex is isoechoic to liver, and the cen- and other abdominal structure visualization is trally located renal sinus is hyperechoic to sur- required. Renal tumors tend to be detected with rounding renal parenchyma. greater confidence on delayed images than on Similar to other structures, use of an intra- early-phase images. One solution is to obtain vascular US contrast agent (such as Levovist; images during both phases (corticomedullary Schering AG, Berlin, Germany) enhances vascu- and nephrogram), but whether the extra com- lar signals and makes vascularity more evident. plexity and cost justify such an approach for a Diagnostic accuracy is improved, especially for limited gain is not clear; a decision based on hyperechoic tumors and complex cysts. individual indications appears reasonable. Doppler US provides data for the intrarenal Renal CT performed shortly after excretory arterial blood flow resistive index (RI) and pul- urography—called CT urography—is a varia- satility index (PI). These indices increase with tion of delayed-phase CT combining high age, acute obstructive uropathy, use of certain spacial resolution of conventional filming with drugs, and in some nephropathies. high contrast resolution of CT. Even pyelove- Endoluminal US using a high-frequency nous backflow can be identified on CT urogra- transducer housed in a catheter and advanced phy (2). Only about half of renal parenchymal endoscopically into a ureter is moving from tumors identified on CT are detected on the pre- research into clinical practice. Potentially, the vious excretory urogram, but such a combina- information obtained helps guide biopsy and tion study tends to increase the clinicians’ laser therapy and defines vessels adjacent to a confidence in some findings. A variant of this ureter. technique is to obtain delayed postcontrast coronal images or a delayed CT scout image. Validity of these various combined procedures Magnetic Resonance Imaging in evaluating hematuria is yet to be established in larger studies. Currently for most suspected renal conditions Furosemide-enhanced CT urography, ob- CT is performed rather than magnetic reso- tained 10 minutes after contrast agent injection, nance imaging (MRI), but MRI is used in a outlines pelvicaliceal structures and identifies setting of contrast allergy or renal failure, and calculi inside opacified urine and differentiates for studying some complex masses. It is also them from phleboliths (3). useful in evaluating venous thrombosis in a Three-dimensional CT imaging techniques setting of renal carcinoma. It provides both are useful both in evaluating suspected tumors spatial resolution and information on renal 573

KIDNEYS AND URETERS function and potentially is more useful than good correlation exists between MR renography either CT or nuclear medicine. Magnetic reso- and radionuclide renography results (4). nance applications range from multiphase 3D A general disadvantage of MR in children, magnetic resonance angiography (MRA) to especially younger ones, is the need for seda- evaluate renal artery stenosis and renal perfu- tion. A relative disadvantage in certain renal sion abnormalities, MR nephrography, and MR applications is its poor sensitivity in detecting urography of the renal collecting systems (espe- calcifications. cially useful in posttransplant complications). Surprisingly, diagnostic accuracy in patients Potentially, a single MR study evaluates reno- with a clinical suspicion for renal tumor was vascular disease, assesses renal function, detects comparable when studies were performed using renal tumors,and identifies urinary tract abnor- either a low field [0.2 tesla (T)] or a high field malities, all without radiation exposure. More (1.5T) magnet, although the signal-to-noise and often, however, the specific MR sequences best contrast-to-noise ratios were significantly worse suited for each application are selected. at low field strength (5). Gadolinium diethylenetriamine pentaacetic Conventional acid (Gd-DTPA) is an ionic agent. A nonionic version is also available in some countries. No As with CT, several distinct phases—cortical, significant differences exist in either signal medullary, and pyelocaliceal—are evident after intensity or function between these two agents. IV paramagnetic gadolinium contrast injection. Some investigators add an intermediate cortico- Magnetic Resonance Urography medullary junction phase. Magnetic reso- nance signal intensity normally decreases in the Magnetic resonance urography both without pyelocaliceal phase due to contrast agent con- and with contrast agents is evolving into viable centration. When searching for small renal alternative studies in select patients. No con- tumors, use of a body phased-array coil in com- sensus is yet apparent on which specific MR bination with fast low-angle shot (FLASH) and sequences constitute MR urography. A more fat suppression pre- and postcontrast thin- basic question concerns the role of MR urogra- section MR allow imaging in single breath- phy: Does it have any advantages over conven- holds. Sagittal and coronal plane images tional or CT urography? improve evaluation. A heavily T2-weighted sequence consisting of Both T1- and T2-weighted sequences are rapid acquisition of images obtained in less useful with contrast-enhanced MRI to evaluate than 30 seconds with a relaxation enhancement renal blood flow and renal function. During technique results in solid organs and flowing the early phase, a renal cortex signal increase in fluid being hypointense, and stationary fluid, T1-weighted sequences is matched by a simi- such as urine in collecting systems and ureters, lar signal decrease in T2-weighted sequences; being hyperintense; the entire urinary tract is during later phases, however, T2-weighted visualized on one image without use of contrast sequence signal intensity in the medulla (this technique is also called MR pyelography). decreases markedly. Thus renal cortical blood The urinary tract is depicted even with non- flow can be evaluated with either sequence, but functioning kidneys. A reconstructed 3D image T2-weighted sequences appear more useful in provides an overall view. Magnetic resonance evaluating renal medulla. Presumably increased spatial resolution is superior to that of US. A amounts of contrast in renal tubules account for current limitation of MR urography is that with the medullary decreased signal intensity during the present MR units small calculi are poorly later phase T2-weighted sequences. imaged. Serial dynamic MR gradient echo imaging A breath-hold 1.5T MR half-Fourier acquisi- using a low contrast dose can be used to obtain tion single-shot turbo spin echo (HASTE) an intensity-time curve, similar to radionuclide sequence visualizes renal collecting systems renography. This technique allows assessment and ureters similarly to excretory urography. of split renal function and urinary excretory The HASTE sequences can be used to acquire status and is an alternative to radionuclide images in the axial, sagittal, or coronal planes. renography. Preliminary studies suggest that These MR urography sequences outline non- 574

ADVANCED IMAGING OF THE ABDOMEN functioning urinary tracts that cannot be visu- Several virtual endoscopy techniques are alized with excretory urography and identifies feasible. Using surface-rendering techniques, level of obstruction without the use of contrast unenhanced MR urography data can be pre- agents. This technique is advantageous in eval- sented in a virtual endoscopy format (10). uating hydronephrosis during pregnancy, but Virtual endoscopy of the upper urinary tract future indications will undoubtedly expand. can be reconstructed from T1-weighted 3D Gadolinium chelates are filtered by renal gradient-echo sequences obtained after urinary glomeruli and excreted. One should keep in tract enhancement by IV gadolinium. Such a mind that dilute gadolinium is hyperintense on technique provides an endoluminal view of the T1-weighted images, but when concentrated it calices, ureters, and ureteral orifices. induces a signal loss and becomes hypointense. Also, if one is performing CT shortly afterward, renal excretion of gadolinium can mimic a cal- Scintigraphy culus on noncontrast CT (6). Breath-hold 3D MR urography using fast With its low radiation burden, renal scintigra- gradient echo performed 5 to 10 minutes after phy is commonly used for initial evaluation and injecting only several mL of Gd-DTPA visualizes follow-up in children. Its main advantage over the urinary tracts as hyperintense structures other imaging modalities is that to some degree (7); urinary tract detection was superior to that function can be quantified. obtained with a heavily T2-weighted sequence. Plasma clearance methods estimate overall The ureters can thus be studied either with renal function. Scintigraphy provides an esti- nonenhanced T2-weighted TSE imaging or mate of each kidney function and detects gadolinium enhanced T1-weighted sequences. gross structural defects. Currently scintigra- A preliminary study comparing these two phy is used to evaluate renal vascular hyper- sequences in infants and children found that tension, renal function after transplantation, although the ureters were more often better suspected infection, and, occasionally, obstruc- visualized with the gadolinium enhanced tive nephropathy. sequences, the two sequences are complemen- Radiopharmaceutical agents useful in renal tary (8). MR urography is feasible in young scintigraphy include the following: infants using only oral sedation. MR urography appears useful in patients with an ileal neoblad- Technetium-99m (Tc-99m)-mercaptoacetyl- der. Although the nonenhanced T2-weighted glycilglycilglycine (MAG3) is an all- sequences can detect a point of ureteric purpose renal agent. It is cleared by tubular obstruction, they do not readily establish an secretion and is useful in flow and function etiology—generally additional MR sequences studies. Effective renal plasma flow can be are required. calculated with this radiotracer. It has a Several paramagnetic contrast agents initially role in diuresis renography in neonates and designed primarily for hepatobiliary appli- infants. This compound is excreted vicari- cations, such as Gd-ethoxybenzyl (EOB)- ously by the liver and is then detected in DTPA and Gd–benzyloxypropionic-tetraacetate the gallbladder. In imaging renal allografts, (BOPTA) initially function as extracellular Tc-99m-MAG3 results in better image agents and are then eliminated via biliary and quality than Tc-99m-DTPA. renal pathways. Thus MR urography using Tc-99m–L,L-ethylenedicysteine (L,L-EC) is a Gd-BOPTA–enhanced breath-hold 3D FLASH newer renal tubular tracer used as an alter- sequences was comparable to conventional native to Tc-99m-MAG3. It has similar excretory urography (9); caliceal fornices were excretion characteristics but higher plasma better visualized with conventional urography, clearance than MAG3. It is also used to but MR urography was superior in the distal obtain the effective renal plasma flow rate. ureters and the bladder, and in evaluating In patients with chronic renal failure, obstructive causes. image quality is similar to that of Tc-99m- A further refinement is the use of a diuretic MAG3. agent. Even a nondilated urinary tract is Tc-99m-DTPA is filtered by glomeruli and the visualized. glomerular filtration rate can be calculated. 575

KIDNEYS AND URETERS

Scintigraphy outlines renal and collecting Tissue cores adequate for histopathologic system anatomy. diagnosis were obtained in 98% of both trans- Tc-99m–2,3-dimercaptosuccinic acid jugular renal biopsies and percutaneous renal (DMSA) binds to proximal tubules and biopsies (13); transjugular renal biopsies are an results in prolonged renal retention. Its option in patients with contraindications or use in planar imaging allows evaluation failure of percutaneous biopsy and in those of focal functional disorders and gross requiring multiorgan biopsies. parenchymal damage. In children, planar Tc-99m-DMSA is useful in estimating renal function. Single photon emission Percutaneous computed tomography (SPECT) Tc-99m- Nephrostomy/Stenting DMSA scintigraphy is more effective than planar in detecting renal cortical defects. Percutaneous nephrostomy is commonly per- Tc-99m-glucoheptonate is also used as a renal formed for emergency decompression of an imaging agent. Neither glucoheptonate nor obstructed urinary system. It is an integral part DMSA is taken up by renal cysts or neo- of several interventional procedures such as plasms, and these appear as defects. percutaneous nephrolithotomy, ureteral stent- ing, and dilation. It is feasible in children and Iodine-131–ortho-iodohippurate (OIH) is an adolescents on an outpatient basis; one study older agent that has been replaced to a excluded outpatient nephrostomies in a setting large degree by Tc-99m-MAG3. of infection, stone therapy, solitary kidney with Carbon-11 acetate positron emission tomog- renal failure, and similar reasons (14). A punc- raphy (PET) imaging reveals prompt renal ture success rate of almost 100% is common. At uptake even in a setting of reduced renal times a nephrostomy is necessary with a nondi- function. lated system, such as a ureteral leak or fistula; fluoroscopy or US-guided injection of air or Biopsy carbon dioxide into nondependent calyces aids catheter insertion (15). Image-guided percutaneous renal biopsy is Double-J stents are commonly used to treat useful in obtaining tissue from suspected small ureteral obstruction. These stents are inserted lesions, and at times such a biopsy replaces retrograde by an urologist or antegrade by an surgical exploration. Most biopsies differentiate interventional radiologist. At times a guidewire between benign and malignant disease and passes through an obstruction but the catheter between primary renal cell carcinoma and fails to do so; a combined retrograde and ante- metastatic disease, or they confirm renal grade approach may then be successful. involvement by lymphoma. If needed, several Both self-expandable and balloon expandable biopsies are obtained at the same time. Com- metallic stents are used for palliation of malig- puted tomography or US–guided 18-gauge nant ureteral obstruction. needle biopsies provide adequate biopsy mate- Complications of percutaneous nephrostomy rial for analysis in most patients. Negative per- tube placement include hemorrhage requiring cutaneous biopsy results in small (<3cm) and transfusion,a complication minimized by main- large (>6cm) tumors, however, should be taining a platelet count above 100,000/mm3. viewed with caution (11). Renal biopsy with an Inadvertent enteric puncture occurs occasion- automated device using a 14-gauge needle in ally. Long-term obstructions include urothelial renal allografts and native kidneys has a >95% hyperplastic reaction and tumor ingrowth or tissue recovery rate, but is associated with a invasion of one stent end. serious complication rate of about 3% (12), In a setting of unresectable pelvic cancer or including death, loss of renal allograft, major radiation or both, a permanent percutaneous hemorrhage (requiring blood transfusion) and nephrostomy is often an option for a variety creation of an arteriovenous fistula. of conditions, including unresectable pelvic fis- In patients at high risk, a transfemoral vein tulas and incontinence. Many of these patients biopsy using flexible forceps is an alternative already have distal urinary tract obstruction. approach. If not, ureteral occlusion is achieved using a 576

ADVANCED IMAGING OF THE ABDOMEN percutaneous approach and a permanent The rare unipapillary kidney has a solitary external diversion is then provided. Complica- calyx and papilla. It is more common on the tions include nephrostomy catheter occlusion left side. Almost always other abnormalities are and retrograde coil migration into the renal present, including megaureter, ectopic ureter pelvis. with vesicoureteral reflux, and renal agenesis on the contralateral side. Imaging of renal agenesis reveals an empty Congenital Abnormalities renal fossa; keep in mind that an ectopic kidney also presents with an empty renal fossa. Preva- Screening for Congenital lence of ipsilateral adrenal gland absence is Abnormalities slightly greater with renal agenesis than in the general population; when present, the ipsilateral Ultrasonography screening for congenital geni- adrenal gland tends to be more elongated than tourinary abnormalities is a simple procedure usual. On the left side the colon splenic flexure but it is rarely performed during a routine tends to fill an empty renal fossa. health check-up. Major anomalies can be A congenitally solitary kidney is about 1.8 expected in under 1% of infants, including times heavier than a normal kidney. The diam- unilateral renal agenesis, vesiculoureteral eter of its glomeruli and convoluted tubules are reflux, hydronephrosis or megaureter, horse- similar to that of a control, but a solitary kidney shoe kidney and ureterocele. contains twice as many glomeruli. The congen- Fetal MRI can evaluate for oligohydramnios ital solitary kidney is thus hyperplastic and not or anhydramnios and congenital genitourinary hypertrophic. anomalies (16). It is currently underused. The imaging approach in a child with a sus- pected single kidney is not clear; a point can be Renal Agenesis made for initial US followed by MR urography. Children with unilateral agenesis are prone to Renal malformation includes the absence of vesicoureteral reflux on the contralateral side, renal tissue (aplasia) or the presence of undif- with reflux being detected in over one third. A ferentiated renal tissue (dysplasia). Bilateral voiding cystourethrogram is thus recom- renal agenesis is incompatible with life; many of mended even if neither infection nor hydro- these babies are stillborn and tend to have a nephrosis is evident. characteristic oligohydramnios-induced Potter facies and numerous other anomalies (Potter sequence). Incidentally, Potter sequence is also Hypoplasia seen with bilateral renal hypodysplasia, severe Simple hypoplasia implies a small but otherwise obstructive uropathy, and polycystic kidney normal kidney. It is a rare anomaly. The number disease, but an occasional such baby survives. of calyces tends to be reduced. Focal hypoplasia Although sporadic, agenesis is more common in entails a reduction in the number of calyces and males, and a familial pattern is identified in associated renal parenchyma. Some patients about one third of patients.In a broader context, have a small kidney that also has segmental renal agenesis is lumped together with dysgen- parenchymal thinning and an associated dilated esis and it is called hereditary renal adysplasia collecting system in this region; the appearance (multicystic dysplasia is discussed in a later mimics that of chronic pyelonephritis. section). In the rare oligonephronic hypoplasia, the Unilateral renal agenesis is relatively com- kidneys are small and contain only one or two mon (about one in 1000 births), with the single calyces. kidney compensating through hypertrophy. In some individuals renal agenesis is the end result of an involuted multicystic dysplastic kidney. Duplicated Collecting System Renal agenesis is associated with an ipsilateral seminal vesicle cyst and ipsilateral ovarian dys- Duplication anomalies range from a bifid col- plasia. Bladder duplication is also occasionally lecting system to duplication of both kidney and found with renal agenesis. ureter. Most duplications are unilateral; if bilat- 577

KIDNEYS AND URETERS eral,they tend to be asymmetrical.A duplication reimplantation, with some surgeons performing is considered incomplete if the two ureters join an ipsilateral ureteroureterostomy. before inserting at one bladder orifice. In a com- plete duplication both ureters insert separately. Duplications are familial and are more common Ectopia in women. In most patients a functioning dupli- Kidneys cated system is a curiosity, and whether to consider an otherwise unremarkable duplicated Ectopia means an abnormal location for a struc- system as part of a normal spectrum is a matter ture. Ectopic kidneys range in location any- of opinion. where from just inferior to the diaphragm to Partial duplications have a Y configuration. the pelvis. A rare renal ectopia is intrathoracic; Much rarer are inverted-Y partial ureteral these are more common on the left and in males. duplications, with the two duplicated lower The lack of imaging detection of a kidney in its ureteral segments inserting either in an ortho- usual location should not be assumed to repre- topic or ectopic location. Perhaps rarest of all is sent agenesis; the entire abdomen needs to be ureteral duplication with blind superior and scanned for an ectopic kidney, which at times is inferior ends (17). small and poorly functioning. Duplications are difficult to detect on pre- Malrotation of a normally positioned kidney contrast axial CT. Postcontrast visualization of is generally a curiosity of little significance. two ureters provides a clue to the presence of a An ectopic kidney undergoes incomplete duplication. Postcontrast CT coronal views and rotation around its axis (it is thus malrotated), conventional radiographs offer another clue: and the renal pelvis tends to face more anterior the uppermost lower pole calyx (which is gener- than usual. The renal collecting system does not ally the kidney’s middle calyx) is located more drain as readily as in a normally situated kidney, lateral than expected, and as a result the kidney relative stasis ensues, and thus an increased axis is more vertical than expected. Consider- prevalence of stone formation is found in these able calyceal distortion occurs with grade 5 kidneys. Ureteropelvic junction obstruction is reflux, and counting the number of calyces is an also relatively common. These kidneys tend unreliable way to detect a duplication. to be dysplastic and some are associated with Neither US nor scintigraphy has sufficient other malformations. resolution to reliably detect most duplications. In renal ectopia the ureter length is appropri- Magnetic resonance coronal views are useful ate for kidney position; in renal ptosis the ureter in a setting of poor renal function; thus T2- appears more tortuous and is more appropriate weighted images reveal fluid-filled upper and to a normally positioned kidney. lower pole structures. A normal US renal sinus echo complex is With a complete duplication the lower renal absent in two thirds of ectopic kidneys, while in pole is generally larger and its draining ureter the other one third it is eccentric in location. inserts in a normal position at the bladder trigone. The upper pole ureter inserts abnor- Crossed Ectopia mally in a more caudal position in the bladder, urethra, or adjacent structures. A ureterocele is In crossed renal ectopia both kidneys are on one a common associated anomaly. The upper pole side of the abdomen. They are usually partly ureter obstructs more often than the lower fused and the ectopic kidney malrotated. The pole ureter; most obstructions are in the distal ureter from the ectopic lower kidney crosses portion of the ureter, although at times an the midline and usually inserts in its normal obstruction occurs at the ureteropelvic junction position. Such crossed fused renal ectopia is and involves either ureteral segment. Similar to an uncommon congenital anomaly generally a normal system, a transitional cell carcinoma of little or no clinical significance. In some, can develop in a completely duplicated collect- however, renal ectopia is associated with other ing system, leading to a complex imaging congenital abnormalities, including ectopic appearance. ureteral insertion. Therapy for obstruction or reflux of a single Ultrasonography of crossed fused renal ureter in a duplicated system is common sheath ectopia identifies an empty renal fossa and a 578

ADVANCED IMAGING OF THE ABDOMEN distorted, enlarged kidney with a duplicated detection is difficult at best. At times an ectopic renal sinus. At times the ectopic kidney is insertion is suggested indirectly by severely difficult to identify with US due to malrotation. deformed adjacent structures. Technetium-99m-DMSA shows an empty renal fossa and outlines the functional status of an ectopic kidney. Ectopia A right retrocaval ureter passes posterior to Horseshoe Kidney the vena cava and courses inferiorly in a more A horseshoe kidney is a type of ectopia con- medial position than usual. Most patients with sisting of partial fusion of the two kidneys a retrocaval ureter are asymptomatic, and occurring in about 0.25% of the population. this condition is discovered incidentally during The lower poles of both kidneys extend more either urography or CT. A rare anomaly is a left medially than usual and either have fused retrocaval ureter associated with a left inferior renal parenchyma or are connected by fibrosis. vena cava. Fusion is anterior to the aorta, and the kidneys Ectopic insertion of a single ureter is into any tend to be more inferior in location than usual. adjacent structure proximal to the external ure- Each kidney has its own collecting system. thral sphincter. It occurs more often in males Often multiple and complex renal arteries and occasionally is associated with prostatitis are present. Rarely, associated inferior vena or epididymitis. Some are associated with other cava anomalies or a retrocaval ureter are also anomalies, such as a crossed single ectopic present. ureterocele. The kidney drained by such an Neoplasms do develop in a horseshoe kidney, ectopic ureter tends to be dysplastic. probably at the same incidence as in normal An ectopic duplicated ureter is more common kidneys although transitional cell carcinomas in females and is more often on the left. The occur somewhat more often than expected. The ectopic ureter usually drains the upper pole of diagnosis of a transitional cell carcinoma is gen- a duplex kidney and tends to insert into the erally made at an advanced stage in these urethra distal to the urethral sphincter, thus patients. Patients with a horseshoe kidney also accounting for urinary incontinence. Occasion- appear more prone to developing a primary car- ally found are intraprostatic and vaginal ectopic cinoid tumor. insertions. Urolithiasis developing in patients with a Even if the distal end of an ectopic ureter is horseshoe kidney is treated with either percu- not stenotic, a low-inserting ectopic ureter can taneous nephrolithotomy or extracorporeal be obstructed by an adjacent urethral sphincter. shock-wave lithotripsy (ESWL), similarly to Huge ureters terminating in the posterior those in patients with normal kidneys. urethra are occasionally found. A bone scan in a patient with a horseshoe Detecting most ectopic ureters with imaging kidney can mimic bone metastases.An apparent should be straightforward, yet delayed detection horseshoe kidney (pseudo–horseshoe kidneys) of an infrasphincteric ectopic ureter is not is seen in patients with spina bifida; gibbus uncommon, especially in girls. Delayed, inap- deformity causes lower renal pole medial propriate and misleading imaging contribute to migration. In these patients, however, the preva- this problem. Technically excellent excretory lence of true horseshoe kidneys is also some- urography is generally diagnostic, although what increased. problems occur with a ureter draining a dys- plastic kidney. Contrast enhanced CT or 99mTc- DMSA scintigraphy aid detection of an ectopic Ureters insertion if a dysplastic kidney is present. Ureteral Bud Remnants With a sufficiently small and poorly func- tioning renal segment, an occult ectopic ureter A ureteral bud remnant associated with renal and its insertion can be difficult to visualize agenesis or dysplasia is usually identified with a with imaging. Problems also arise with un- retrograde study, provided reflux exists. In the usual insertions and with a poorly func- absence of reflux or with an ectopic insertion, tioning kidney. Some insertions are only 579

KIDNEYS AND URETERS transiently visible on one of several imaging ment, dysplasia is limited to the infundibula, studies. Vaginography defines the insertion of renal pelvis, and proximal ureter, or it involves some ectopic vaginal ureters because these a kidney to the point that dilated calyces appear ureters tend to reflux. Occasionally MRI is as intrarenal cysts. Segmental multicystic dys- useful, such as with an ectopic ureter from a plasia occurs in a setting of a duplex collecting poorly functioning upper pole duplicated system. At times a hypoplastic renal artery is kidney that is not detected with IV pyelography identified. and US. Most often multicystic dysplasia is detected A triple ureter, with an ectopic opening into as an abdominal tumor in infancy. Some older the vagina has been described (18). patients present with ureteropelvic junction Ectopic ureteroceles are discussed in Chapter obstruction. The condition is discovered in an 11. occasional adult as an incidental finding. A variant of multicystic dysplasia includes an associated hydronephrosis, with renal cysts Nephroptosis communicating with the renal pelvis. This con- dition presumably develops from incomplete One can be criticized for including nephrop- ureteral obstruction. Often some renal function tosis, or floating kidney, as an abnormality. is evident. Older physicians are undoubtedly familiar Among term neonates and infants with uni- with this condition and the resultant attempts lateral multicystic dysplastic kidneys, in those to cure it by nephropexy, a procedure that is with no vesicoureteral reflux the contralateral considerably less common today. Recently, kidney was more than 1 standard deviation however, a few reports have described laparo- longer than the mean for age in 54% (19). Con- scopic nephropexy as therapy for symptomatic tralateral vesicoureteral reflux is detected in nephroptosis, and this procedure is again some- 15% to 25% of children with a newly diagnosed what in vogue. multicystic kidney, and these refluxing kidneys Occasionally nephroptosis is a cause of are significantly shorter than nonrefluxing chronic ureteral obstruction and associated ones. Other anomalies include ectopic ureters, symptomatology. ureterocele, bladder diverticula, and urethral duplication. An association exists among renal dysplasia, Gartner’s duct cyst, and ipsilateral müllerian duct obstruction. An investigation Multicystic Dysplasia for lower urinary tract abnormalities is thus in Clinical order in these infants. Extraurinary anomalies include bowel malrotation and congenital Fetal kidney nephrons form from fetal meta- cardiomyopathy. nephric blastema surrounding the ureteral bud. Renal malignancy is rare in multicystic dys- This fetal blastema normally matures during plasia, and current opinion is that this condition gestation, but occasionally some persists after is not premalignant, although the kidney birth as nephrogenic rests. These nephrogenic appears prone to nodular renal blastema and rests are associated with an increased risk reports suggest that renal cell carcinoma, of multicystic dysplasia, multilocular cystic Wilms’tumor,and even mesothelioma appear to nephroma, and Wilms’ tumors. They are more be more common than by chance alone. Com- common in several syndromes, such as plicating the issue is that occasionally other Beckwith-Wiedemann syndrome (discussed in lesions, including tumors are misdiagnosed as a later section), hemihypertrophy, and sporadic multicystic dysplasia. aniridia; children with these syndromes should The current trend is to follow segmental be screened for Wilms’ tumors. multicystic kidneys nonoperatively because Complete multicystic dysplasia (also called these cysts tend to involute and the kidney multicystic kidney, renal dysplasia, and renal decreases in size. With age, some patients dysgenesis) is found only unilaterally— develop extensive calcifications. At times by complete bilateral involvement is incompatible adulthood only a cystic remnant with a calcified with life. Depending on the extent of involve- rim is apparent. 580

ADVANCED IMAGING OF THE ABDOMEN

history of renal disease is obtained in about half the patients, and variable penetrance and expressivity are apparent. Many of these patients develop hypertension. Renal failure is a late finding. These patients are also prone to developing aortic and cerebral aneurysms with their related complications. A rare disorder called oral-facial-digital syn- drome type 1 includes polycystic kidney disease as one component. The syndrome is X-linked, with affected males dying before birth. Although renal findings resemble autosomal polycystic disease and a dominant inheritance pattern is evident, histopathology reveals Figure 10.1. Right multicystic dysplastic kidney. Noncontrast mostly glomerular cysts (20). computed tomography (CT) identifies a small, irregular right There are two subtypes of autosomal- kidney (arrow). (Courtesy of Nancy Curry, M.D., Medical Univer- dominant polycystic disease. Polycystic kidney sity of South Carolina.) disease type 2 (PKD2) has a milder clinical phe- notype than PKD1; the median age at death or onset of end-stage renal disease is 53 years for Imaging individuals with PKD1 and 69 years for those with PKD2 (21).About half of these patients also A voiding cystourethrogram and renal US develop liver cysts; far fewer develop pancreatic appear appropriate in newborns with suspected or splenic cysts or even adrenal cysts. A rare multicystic kidney disease to confirm the diag- patient also has Caroli’s disease, but this associ- nosis and detect any associated anomalies. The ation is less common than with autosomal- grape-like intrarenal cysts do not communicate recessive polycystic disease. Polycystic kidney with the ureter. Little normal renal parenchyma disease can develop in a horseshoe kidney. is detected in the involved kidney (Fig. 10.1). Histologically, cystic changes occur both in A characteristic finding is a club-like deformity nephrons and collecting ducts. Eventually mul- of a rudimentary ureter. A small dysplastic tiple cysts of varying size are found in both the kidney is more echogenic than a normal kidney; renal cortex and the medulla. Subcapsular cysts the US differential diagnosis also includes also develop. hydronephrosis due to other etiologies. Abdominal pain is a common presentation. Occasionally during renal scintigraphy a mul- Many patients develop hypertension. An occa- ticystic dysplastic kidney accumulates a radio- sional cyst rupture into the collecting system pharmaceutical agent; such uptake correlates leads to hematuria. Enlarged kidneys are with the presence of mature renal cortical tissue palpable in some individuals. Renal stones with in the diseased kidney. their related complications are more prevalent Tc-99m-DMSA renal uptake is decreased than in the general population. Eventually in the contralateral kidney in a majority of renal failure ensues. The rare emphysematous patients with a multicystic kidney, reflecting pyelonephritis is probably due to superim- tubular and glomerular damage. posed infection rather than polycystic disease. Likewise, renal cell carcinoma developing in Polycystic Disease a setting of polycystic disease is probably fortuitous. Autosomal Dominant Typically few cysts are detected early in life, Clinical but gradually multiple bilateral cysts enlarge and interstitial fibrosis develops with loss of Autosomal-dominant polycystic disease, also normal renal tissue. Not uncommonly progres- called adult polycystic kidney disease and Potter sive worsening of renal function manifests in type III, is the most common hereditary renal early adulthood. The cysts compress and distort disorder. It is not a simple entity; no family adjacent calyces and eventually little renal 581

KIDNEYS AND URETERS parenchyma is detected.Why the loss of normal Computed tomography or MR is useful to renal tissue is part of this condition is puzzling. evaluate for any associated liver disease. Still, the kidneys are larger than normal. The sensitivity of renal US in individuals Several criteria are used to identify patients under 30 years of age at risk for autosomal- at risk for developing adult polycystic kidney dominant polycystic kidney disease was 95% for disease. One scheme is that the presence of at those with PKD1 but only 67% for those with least two renal cysts (either unilateral or bilat- PKD2, but US sensitivity for either PKD type in eral) in individuals at risk and younger than 30 individuals aged 30 years or older was 100% years is regarded as sufficient to establish the (22); DNA genetic linkage analysis was the gold diagnosis; in those 30 to 59 years of age at least standard. two cysts in each kidney and in those above 60 These cysts vary from hypo- to hyperintense years of age at least four cysts in each kidney are both with T1- and T2-weighted images, pre- required. Ultrasonography can be used to sumably due to prior hemorrhage (Fig. 10.3). A screen for these cysts. fluid-fluid level is identified in some.

Imaging Therapy Initially cysts are small, but eventually imaging Follow-up of these patients is generally by US. identifies bilateral enlarged kidneys, at times Computed tomography is useful to evaluate for markedly asymmetrical, and containing multi- a suspected complication. Intravenous urogra- ple cysts. The cysts vary in size and distort sur- phy has no role in follow-up. rounding parenchyma. Computed tomography Open transperitoneal bilateral renal cyst shows most cysts to resemble simple cysts, reduction surgery is an option in symptomatic although hemorrhage into cysts is common and patients; one advantage of this approach is that these are hyperdense to water (Fig. 10.2). Some any liver cysts are also amenable to therapy. have a fluid–fluid level or even appear as a solid Laparoscopic cyst unroofing (decortication or tumor. Renal calcifications are generally sec- marsupialization) for relief of pain is also an ondary to calculi, prior hemorrhage into a cyst, option; intraoperative US aids cyst detection or cyst wall calcifications. during the laparoscopic procedure. Some of these patients require repeat cyst unroofing before pain relief is achieved. A number of these patients eventually undergo renal transplantation. Some surgeons recommend nephrectomy prior to renal trans- plantation, although others disagree and reserve nephrectomy for those with intracystic hemor- rhage, significant hematuria, pyonephrosis, or other complications.

Autosomal Recessive Also known as Potter type I and infantile poly- cystic disease, the autosomal-recessive form of polycystic kidney disease manifests early in life. The underlying defect is renal tubular ectasia. The nephrons are normal. Expressivity varies, with some patients not surviving beyond the neonatal period. Those with milder renal involvement survive longer and develop hepa- Figure 10.2. Polycystic disease. Transverse CT image through tobiliary fibrosis and dilated bile ducts. Thus the the kidneys reveals numerous cysts varying in size. Little renal severe form detected in infancy results pri- parenchyma is left.(Courtesy of Patrick Fultz, M.D., University of marily in renal involvement, called infantile Rochester.) polycystic disease, while in older children liver 582

ADVANCED IMAGING OF THE ABDOMEN

A B

Figure 10.3. Polycystic disease. A: Cysts, hyperintense on T2–weighted magnetic resonance imaging (MRI), have replaced most of renal parenchyma. Even more hyperintense cysts are present in the liver. B: Very little renal parenchyma is left to enhance after IV contrast.(Source: Burgener FA,Meyers SP,Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.) C: T2– weighted MRI in another patient with polycystic kidneys identifies cyst intensity variations reflecting their content differences. C (Courtesy of Patrick Fultz, M.D., University of Rochester.)

changes predominate and this entity is labeled identifies similar findings. Both CT and MRI juvenile form or congenital hepatic fibrosis (see also help detect any hepatic fibrosis and dilated Caroli’s disease, discussed in Chapter 7). Yet bile ducts. whether autosomal-recessive polycystic kidney Ultrasonography in the infantile form shows disease and congenital hepatic fibrosis are bilaterally enlarged and diffusely hyperechoic indeed the same entity but with different kidneys, a pattern that in these infants strongly manifestations is not clear. Some adults with suggests the diagnosis. High-resolution US autosomal-dominant polycystic disease and reveals dilated ectatic tubules arranged radially those with multicystic dysplasia also develop perpendicular to renal capsule, with the periph- similar hepatic fibrosis. eral renal cortex initially not involved because it In the infantile form numerous small cysts normally does not contain collecting ducts. (several millimeter range) develop throughout, In surviving infants (presumably those the kidneys are markedly enlarged, poor func- having the juvenile form), the initial abnormal- tion is evident early on, and renal failure grad- ities tend to be limited to the kidneys, but grad- ually ensues. ually the disease focus shifts as hepatic damage Computed tomography reveals renal cysts to leads to portal hypertension and its sequelae. be near water density unless superimposed Serial US in the juvenile form reveals that bleeding occurs. Magnetic resonance imaging initially enlarged kidneys either shrink in 583

KIDNEYS AND URETERS size or remain stable with age; renal echogen- found in older children and adults and probably icity approaches that seen in patients with represents an acquired type of glomerulocystic autosomal-dominant polycystic kidney disease disease. Whether this is the same entity seen in but without marked kidney enlargement. infants is conjecture. In fact, glomerulocystic disease is probably much more common than the relatively small number of published cases Alport’s Syndrome suggest; in adults it may be asymptomatic and Alport’s syndrome is an inherited, degenerative only becomes symptomatic when another con- disorder involving basement membrane colla- dition, such as lupus glomerulonephropathy or gen that lacks Goodpasture antigen. Both hemolytic-uremic syndrome, is superimposed. sex-linked dominant and autosomal-recessive The diagnosis is suggested by renal biopsy, forms are described. Electron microscopy– although histopathology is not always straight- observed anomalies are almost specific for this forward. In addition to glomerulocystic kidney syndrome. It is linked to Goodpasture’s disease, disease, renal cysts are found in autosomal- an uncommon autoimmune condition also recessive polycystic kidney disease, autosomal- showing a similar basement membrane collagen dominant polycystic kidney disease, and diffuse abnormality. In a broader context, this syn- cystic dysplasia. drome is linked to antiglomerular basement In the neonate, both polycystic diseases membrane disease and thin basement mem- and glomerulocystic disease result in bilaterally brane disease, both diseases being more enlarged hyperechoic kidneys. High-resolution common than Alport’s syndrome. US detects small, isolated cysts in a hyperechoic Symptoms start in childhood. Hematuria and renal cortex, with these cysts usually being proteinuria eventually progress to renal failure. smaller than those found in typical autosomal- Imaging identifies small, smooth kidneys dominant polycystic kidney disease. Also, these with poor function. cysts extend to the periphery, but no cysts are seen in renal medulla, which distinguishes this condition from both autosomal-recessive and Alagille’s Syndrome -dominant polycystic diseases. Alagille’s syndrome, or arteriohepatic dyspla- sia, is discussed in more detail in Chapter 8. These patients also develop tubulointerstitial Medullary Cystic Disease nephritis and renal tubular acidosis. An occa- Renal medullary cystic disease consists of a sional manifestation is resultant renovascular spectrum of abnormalities eventually leading hypertension. to renal failure. These patients have progres- Angiography reveals uni- or bilateral renal sive renal tubular atrophy. Two forms are artery stenoses and abnormalities in the aorta described: a juvenile form (also called juvenile and celiac superior mesenteric and subclavian nephronophthisis) inherited as an autosomal- arteries. Some patients develop bilateral renal recessive trait manifesting in childhood, and an cysts and aortic wall calcifications at an early adult form inherited as an autosomal-dominant age. trait. A tubulointerstitial nephritis develops in both forms. Gross medullary cysts are found Glomerulocystic Disease in the adult form, while smaller cysts develop in the juvenile form. Both sporadic and familial glomerulocystic In the juvenile form US reveals increased disease develop. The hallmark of this disease echogenicity secondary to the small cysts. The is dilation of Bowman’s space and proximal corticomedullary junction is poorly differenti- convoluted tubules. Numerous glomerular cysts ated. Urography shows decreased contrast develop but without dysplasia. Affected infants excretion, and pyelography identifies tubular have enlarged kidneys. Liver cysts may be ectasia.Renal size tends to decrease with disease present. progression, and corticomedullary cysts Glomerulocystic disease associated with became evident. These cysts are better defined either hypoplastic or normal-sized kidneys is with CT and MRI than with US. 584

ADVANCED IMAGING OF THE ABDOMEN

Because US abnormalities appear before clin- Von Hippel-Lindau Disease ical symptoms or signs are evident, US is useful in screening suspected families. Von Hippel-Lindau disease is a hereditary Biopsy suggests the diagnosis. cancer syndrome caused by mutations of the VHL tumor-suppressor gene, which is located Familial Glomerulosclerosis (Familial on the short arm of chromosome 3. The VHL Nephrotic Syndrome) gene produces a tumor-suppressor protein, called pVHL, which plays a role in angiogenesis, In the nail-patella syndrome, nail and skeletal cell cycle regulation, and other functions, and abnormalities are associated with a nephropa- regulates both growth and differentiation of thy. Renal biopsy reveals glomerulosclerosis, kidney cells. Mutations of the VHL gene are also and electron microscopy identifies massive found in mesotheliomas and small cell lung fibrillar collagen within a mesangial matrix and carcinomas. Nevertheless, the etiology of von basement membrane, a hallmark of this condi- Hippel-Lindau disease appears to be more tion. Similar changes are also found in some complex than currently apparent because a patients with proteinuria and hematuria but germ cell mutation is identified only in 70% of without other stigmata of nail-patella syn- affected patients. Also, systematic investigation drome. These patients have mild proteinuria of families of involved individuals often detects early in life, and nephrotic syndrome becomes additional silent tumors. apparent during the second or third decade. This autosomal-dominant disease has age- related penetrance of close to 100% at age 60 Tuberous Sclerosis years. Affected individuals develop central nervous system hemangioblastomas, retinal Tuberous sclerosis, or Bourneville-Pringle angiomas, pancreatic cysts and islet cell tumors, disease, is a neurocutaneous disorder having adrenal pheochromocytomas and paragan- an autosomal-dominant inheritance, although gliomas, epididymal cystadenomas, and in the spontaneous mutations also occur.Mental retar- kidneys cysts and clear cell carcinomas. Only a dation and seizures are part of multiorgan subgroup of these patients is at increased risk involvement and renal lesions are common, for developing a pheochromocytoma. Thus consisting mostly of angiomyolipomas and these patients are subdivided into type I cysts. Prevalence of lymphangioleiomyomatosis (without pheochromocytoma) and type II (with is also increased in tuberous sclerosis. Imaging pheochromocytoma). in affected individuals begins to identify renal Renal cysts are often multifocal and bilateral lesion during early childhood and most indi- and are predominantly cortical in location. viduals have developed renal tumors by late They do not progress to renal failure. There is, childhood. Most common are angiomyolipo- however, an increased prevalence of neoplasms mas, followed by simple renal cysts. in these cyst-containing kidneys. Multicentric An occasional cyst disappears during follow- renal cell carcinomas are common, at times up but angiomyolipomas do not. Although gen- bilaterally. erally believed that these patients are not at Among patients with von Hippel-Lindau increased risk for renal cell carcinomas, anec- disease having renal cell carcinomas, cancers dotal reports of renal malignancies abound. occur 25 years earlier, are more often associated An occasional patient has multiple cysts to with renal cysts, and tend to be multifocal and the point of mimicking polycystic disease. bilateral, but have a lower grade histology and Angiomyolipomas are prone to bleeding and better 10-year survival than unselected pati- forming hematomas. Eventually renal insuf- ents with renal cell carcinoma (23); metastases ficiency and renal failure ensue if sufficient occurred in von Hippel-Lindau disease patients parenchyma is replaced by cysts and tumors. only when tumors were >7cm in diameter. A rare first presentation is an elderly patient These tumors tend to be encased by a fibrous with gradual renal failure and imaging capsule. detecting marked bilateral renal parenchy- The treatment of cysts and tumors in this mal distortion due to multiple cysts and disease has become rather conservative and angiomyolipomas. differs from conventional therapy. Many asymp- 585

KIDNEYS AND URETERS tomatic lesions are observed rather than overall appearance mimics that seen in chronic resected, and CT, US, and MRI are used for pyelonephritis. screening, follow-up of known lesions, and Adjacent hematomas are secondary to overall management of these patients, keeping retroperitoneal bleeding. in mind that CT and especially US miss small tumors in these patients. A renal carcinoma is resected only when it has grown to a certain Beckwith-Wiedemann Syndrome size. Over the last several decades surgery in these patients has evolved from radical nephrec- Beckwith-Wiedemann syndrome is a congenital tomy to a nephron-sparing operation. A radical overgrowth syndrome with a high sporadic nephrectomy is reserved for larger or more occurrence, manifesting variable expressivity. numerous tumors; follow-up consists of CT, There is a Beckwith-Wiedemann registry at chest radiography, and renal function tests the National Cancer Institute. Common abnor- every 6 months. malities include macroglossia, abdominal wall These patients develop end-stage renal failure defect, large birth weight, nephromegaly, and both from surgical therapy and from tumor less often hemihypertrophy. growth. Theoretically, transplantation with its Affected children are prone to developing associated immunosuppression may predispose childhood solid tumors, including Wilms’ to tumor recurrence, but in practice this does tumor, adrenocortical carcinoma, and hepato- not occur. blastoma. An occasional child has a sarcoma or renal cell carcinoma. One should keep in mind, however, that not all renal tumors in these patients are malignant. Benign renal abnormal- Sickle Cell Disease ities, consisting of renal cysts, caliceal divertic- The primary kidney abnormality in sickle cell ula, hydronephrosis, and nephrolithiasis, occur disease is small vessel involvement leading to in approximately 25% of these patients; most renal function impairment. The hemolysis these patients are asymptomatic. patients experience also results in glomerular hemoglobin deposition. Findings in other organs, primarily spleen, are common. Pati- Bartter’s Syndrome ents with heterozygous or homozygous sickle The rare Bartter’s syndrome leads to hypo- cell disease develop enlarged kidneys, focal kalemia and increased plasma renin and angio- infarcts, cortical necrosis, and progressive renal tensin II levels. It should be suspected in a child insufficiency. with nephrocalcinosis and a history of polyhy- Most teenagers with sickle cell disease have a dramnios and premature delivery. normal renal US appearance, gradually devel- Renal US findings vary; US tends to reveal oping either a focal or a diffuse increase in hyperechoic pyramids or diffuse hyperechoic reflectivity in the renal medulla or throughout kidneys. the kidney, changes similar to those seen in Baseline scintigraphy in one patient was early nephrocalcinosis. Both RI and PI are normal, but pharmacologic blockade of the increased, with findings directly related to renin-angiotensin system with captopril disease severity. revealed a bilateral increase of parenchymal With iron deposition,MR reveals hypointense transit time, time to maximum activity, and signals from renal cortices on both T1- and T2- retained cortical activity (24); the authors weighted images. suggest captopril renography for differentiat- ing Bartter’s syndrome from other causes of hypokalemia. Hemophilia Ultrasonography in hemophilia type A pati- Tyrosinemia ents identifies smaller than usual kidneys and dilated calyces and renal pelves, at times con- A deficiency of fumarylacetoacetate hydrolase taining blood clots. Calculi are common. The leads to tyrosinemia, an autosomal-recessive 586

ADVANCED IMAGING OF THE ABDOMEN disorder especially prevalent in the province the point that one or both ureters dilate mas- of Quebec. Children with this lethal disease sively. The bladder also enlarges. develop central nervous system and liver abnor- Ureteroceles are discussed in Chapter 11. malities early in life. Renal function is often impaired. Megacalyces Computed tomography and US in 32 children with tyrosinemia undergoing liver transplanta- An infant or adult occasionally has calyceal dila- tion revealed enlarged kidneys in 47%, a hyper- tion without concomitant renal pelvis dilation echoic appearance in 47%, nephrocalcinosis in and without underlying obstruction. Whether 16%, and delayed contrast excretion in 64% this condition, also called Puigvert’s disease,is (25); liver transplantation improved renal congenital or acquired is conjecture. Medullary function in about half of these children, but pyramids are thinned and as a result the calyces enlarged kidneys and a hyperechoic appearance have a straight or even convex outline rather persisted. than their usual concave shape. The number of calyces tends to be increased and they have a polygonal shape. The renal pelvis is not dilated Congenital Hydronephrosis and renal function is normal. Megacalyces is and Hydroureter associated with increased stone formation. Intravenous urography defines the condition Many infants with hydronephrosis also have and excludes an obstruction. renal tubular dysfunction, with renal tubular acidosis being most common. Hydronephro- Ureteropelvic Junction Obstruction sis is readily diagnosed by most imaging modalities. The most common congenital urinary tract A congenital urinary tract obstruction obstruction is at the ureteropelvic junction. A evolves while a fetal kidney is still developing. ureteropelvic junction stricture in the very The sequelae of a congenital obstruction thus young may represent a mild form of multicystic result in findings that tend to be different from dysplasia. It is not common. those seen with an obstruction developing later in life. Midureteral Obstruction In newborns with unilateral hydronephrosis, the contralateral kidney ranges from larger than A congenital midureteral obstruction is rare, normal, to normal in size, to small, and such with some of these strictures being classified as findings should be interpreted cautiously. Dis- ureteropelvic junction strictures. A rare associ- tinguishing obstructive from nonobstructive ation exists between ureteral valves and ureteral hydronephrosis in neonates can be difficult. strictures. Congenital adynamic midureteral Without an obvious obstructive site, some of segments are rare. Resection reveals muscular these neonates are followed medically until they disarray but a patent ureter lumen. grow. At times with known prenatal hydronephro- Primary Megaureter sis, renal US performed immediately after birth is falsely negative for hydronephrosis, probably In congenital or primary megaureter a short due to oliguria. Cystourethrography appears nonperistaltic distal ureteral segment results in indicated in these children because of an functional obstruction,while the more proximal increased risk for vesicoureteral reflux. ureter dilates and does have peristalsis. Etiology The term megacystis-megaureter is descrip- for the nonperistaltic segment is unknown but, tive and is most often applied to uncorrected unlike rectal aganglionosis, ganglion cells are vesicoureteral reflux and resultant dilation. present in this segment.Some authors subdivide In this sense it can be either congenital or primary megaureter into the following cate- acquired. Whether it represents a sequela of gories: (1) obstructive, (2) refluxing, and (3) uncorrected massive chronic reflux or is a nonobstructive and nonrefluxing. The degree of residue of a congenital hydroureter is conjec- obstruction varies, and calyces are not dilated ture. Megacystis-megaureter can be extreme to when obstruction is mild. The condition is more 587

KIDNEYS AND URETERS often detected in children than adults and is and, if stable, these patients generally undergo more common on the left side. In some, ureteral CT. Kidney damage due to anterior abdomi- dilation does not progress with age and may nal gunshot and knife wounds invariably also even improve. A rare patient first presents with involves intraperitoneal structures, and most of a ureteral stone in a megaureter and an already these patients are explored. As a result, some nonfunctional kidney. surgeons argue against a need for any preoper- Differential diagnosis includes ureteral ative abdominal imaging studies. Flank or pos- dilation secondary to reflux (megacystis- terior stab wounds, on the other hand, are often megaureter) and distal anatomic ureteral evaluated with contrast-enhanced CT and the obstruction. Generally the distal ureter is not results are used to guide therapy. narrowed in a setting of reflux. At times a ret- rograde study is necessary to exclude anatomic obstruction. Blunt Trauma Clinical Trauma Blunt renal injuries consist of contusion, lacer- ation, rupture, and injury to the renal pedicle. A renal injury classification scale, devised by Ureter rupture due to blunt trauma is rare. the American Association for the Surgery of Most ureteral injury is from gunshot and stab Trauma, is outlined in Table 10.1. New classi- wounds. fications of renal trauma continue to be devised, Renal trauma should be suspected in a setting indicating that there are perceived limitations of shock, hematuria, or adjacent fractures. of the prior systems. Radiologic classifications Several studies have correlated the lack of have also been published. hematuria with absence of major urinary tract In a setting of abdominal trauma, clinical injury, yet occasional patients without hema- evaluation of genitourinary trauma is notori- turia do have urinary tract injury, especially to ously difficult. As a result, at least in the United the renal pedicle and ureter, and the degree of States, trauma physicians are rather generous in hematuria does not correlate with the extent of obtaining screening imaging studies in these the injury eventually detected. Even a major patients, thus achieving a low yield for positive ureteral laceration does not lead to hematuria in studies. about one third of patients. Leakage from the urinary tract results in an accumulation of urine Penetrating Injuries and either a urinoma or urinary ascites ensue. The presence of hematuria, on the other Intravenous urography is insensitive in evaluat- hand, is generally investigated further with ing renal damage from a penetrating injury, imaging studies. Often not only is urinary tract

Table 10.1. Surgical renal injury scale Grade* Type of injury I Contusion Hematuria with normal urologic studies Hematoma Subcapsular, nonexpanding II Hematoma Perirenal, nonexpanding Laceration Parenchymal, <1cm, without urinary extravasation III Laceration Parenchymal, >1cm, without urinary extravasation IV Laceration Extending through cortex, medulla and collecting system Vascular Main renal artery or vein injury with contained hemorrhage V Laceration Shattered kidney Vascular Hilar avulsion with devascularized kidney

*Advanced one grade for multiple injuries, up to grade III. Source: Modified from Moore et al. (26). 588

ADVANCED IMAGING OF THE ABDOMEN

injury present but also multiorgan damage. injection, and perhaps another one in 5 minutes Incidentally, not all red urine represents blood. or so (called “one-shot urography” by some cli- Porphyrins and certain drugs and foods lead nicians) is a fast study to assess gross renal func- to red-colored urine. About 15% of the popula- tion and establish that there are indeed two tion has a genetic predisposition to beeturia, kidneys in an unstable patient, but it is inade- due to the betalaine red pigment found in beet quate to assess for underlying renal trauma root. and should be discouraged in stable patients. It In children, the kidney is the most common is a useful study in unstable patients who then organ injured in blunt abdominal trauma. Com- undergo immediate exploration; their renal plicating the issue is that congenital malforma- status is determined intraoperatively. tions need be considered. Thus underlying Many trauma patients have multiple injuries hydronephrosis or even an extrarenal pelvis and, in the United States and some other coun- predisposes to a laceration or avulsion. tries, if they are hemodynamically stable, A rare cause of nontraumatic ureteral hema- contrast-enhanced helical CT has become the toma is overcoagulation. screening tool of choice. Precontrast images are generally not obtained. An early-phase CT eval- uates the renal pedicle and overall vascularity, Imaging a parenchymal-phase CT detects renal lacera- tions, and a delayed-phase CT provides infor- Intravenous urography is no longer the primary mation about contrast excretion and possible imaging modality for renal trauma, having been extravasation (Fig. 10.4). Such a technique also supplanted by CT, which also evaluates other evaluates injury to the liver, spleen, pancreas, intraabdominal structures. If CT is not readily and adjacent structures. In particular, one available, urography is an alternate for evaluat- should not rely on early-phase images to ing the upper urinary system. A normal IV exclude collecting system injury with contrast urogram essentially excludes major renal and extravasation; delayed scans are necessary. At ureteral injury, although rare instances of severe times delayed serial postcontrast views reveal renal laceration have not been detected with an an increasing CT density or MR signal intensity urogram. in adjacent fluid, confirming extravasation. Limited urography, consisting of a scout In some countries US is the primary imaging radiograph, a radiograph shortly after contrast modality in evaluating renal trauma. Ultra-

A B

Figure 10.4. Perirenal hematoma. A: CT identifies left perirenal fluid in a man who fell down stairs. (Courtesy of Patrick Fultz, M.D., University of Rochester.) B: Contrast-enhanced CT in another patient reveals a focal fluid collection anterior to the left kidney (arrows). (Courtesy of Algidas Basevicius, M.D., Kaunas Medical University, Kaunas, Lithuania.) 589

KIDNEYS AND URETERS sonography can detect major vascular injury, renal fracture, or gross extravasation. It is a common modality in children. Nevertheless, accuracy of US appears to be less than with CT and even iv urography. Currently MRI is not the initial imaging modality in suspected renal trauma, with avail- ability, cost, and imaging time delays being some of the factors involved. Nevertheless, MRI complements CT in some trauma patients, espe- cially those with equivocal CT findings, those who need repeat imaging studies, and those with an iodine allergy. Ureteropelvic junction avulsion consists of complete ureteral transection, and thus no con- trast is identified in the distal ureter, but con- trast extravasation is evident, often perirenal in location. Although ureter nonvisualization is Figure 10.5. Aortography in this patient after a motorcycle at times even a normal finding, in the appro- accident reveals complete left renal artery occlusion (arrow) due to a subintimal tear. No renal function was evident. No extra- priate clinical setting such a finding suggests vasation was seen.(Courtesy of David Waldman,M.D.,University avulsion, and a more specific study of ureter of Rochester.) integrity, such as retrograde pyelography, should be considered. Both contrast extravasa- tion and contrast in the ureter distally signify an ureteropelvic junction laceration. These findings are detected with both urography and postcontrast CT, but in any one patient the dif- ferentiation between avulsion and laceration An associated extraperitoneal hematoma is can be difficult. Differentiation between avul- common. In some centers angiography is the sion and laceration has therapeutic implica- imaging modality of choice with suspected tions because the latter is often managed renal pedicle injury; in others CT is preferred conservatively. (Fig. 10.5). The lack of contrast enhancement At times a preexisting abnormality alters an of renal parenchyma is a hallmark of pedicle otherwise more typical appearance of renal injury, a finding that is not always reliable. Some trauma. A renal cyst is prone to rupturing patients have partial parenchymal enhance- during blunt abdominal trauma, and the patient ment in spite of main renal artery and vein develops either hematuria or retroperitoneal disruption, at times due to an intact accessory hemorrhage. Such trauma-induced rupture of a renal artery, extensive capsular collaterals or renal cyst modifies the appearance of an associ- even flow being maintained by an adjacent ated hematoma. Ultrasonography identifies an hematoma. Computed tomographic detection acute hematoma as an isoechoic or hyperechoic of an extensive extraperitoneal hematoma is tumor mimicking a neoplasm; it becomes more common with a pedicle injury. heterogeneous during resolution. An arterial intimal tear can initially lead to an Renal scintigraphy has a role in detecting intimal flap and evolve into a thrombus. Exten- urinary leaks in patients with a contraindication sive involvement results in a lack of perfusion to IV contrast. It is also often employed in renal and excretion by the kidney involved, although transplant patients. distal ischemia is usually segmental rather than the entire kidney being involved. Occlusion of Vascular Injury the main renal artery or of a main branch is equally well seen either by contrast-enhanced Renal pedicle injury consists of renal artery or helical CT or angiography in most, but not all, major vein laceration, avulsion, or thrombosis. patients. Occasionally helical CT identifies an 590

ADVANCED IMAGING OF THE ABDOMEN abrupt cut-off to the renal artery. Contrast- cations. With continued bleeding, after diag- enhanced helical CT should also detect any nostic angiography establishes a site of hemor- pseudoaneurysms. rhage in patients with traumatic kidney Retrograde flow of IV contrast into the renal injury, transarterial superselective embolization vein suggests renal artery obstruction. should stop the bleeding in most patients. Most Avulsion results in renal infarction. A localized extravasations resolve spontaneously. hematoma surrounds the site of rupture and On the other hand, patients with renal pedicle at times a postcontrast study detects contrast trauma require prompt revascularization to extravasation. Renal artery thrombosis or renal avoid future kidney loss. pedicle avulsion should be suspected with post- Most unrecognized complications manifest contrast nonvisualization of a kidney, although within the first 4 weeks of injury; the excep- an absent kidney, vascular spasm, or simply an tions are hypertension, hydronephrosis due ectopic kidney outside the imaged field results to partial obstruction, infected urinoma, and in similar findings. pyelonephritis. A devitalized kidney segment Ultrasonography of some renal pedicle rup- predisposes to subsequent infection. tures is initially noncontributory, and either CT Injuries to the main renal artery are treated or renal arteriography is required to exclude either by surgical revascularization or conserv- major pedicle injury. atively. Percutaneous insertion of an endovas- Occasionally occult renal injury results in cular stent suffices for some vascular injuries. posttraumatic arterial hypertension. Whether Posttherapy hypertension can be due to either computed tomography angiography (CTA) or an initial injury or a therapy complication. arteriography should be performed is debat- Posttherapy renal function can be confirmed able, although arteriography is considered to be by scintigraphy. the gold standard. Renal artery or major branch laceration or intrarenal artery constriction is detected in some of these patients. Small or Large Kidney(s) Renal vein thrombosis results in an enlarged kidney and a delayed and diminished nephro- At times imaging reveals a kidney that is gram. Renal vein laceration leads to a per- smaller or larger than normal. Some of the con- inephric hematoma that tends to mask the ditions associated with smaller than normal seriousness of an underlying vascular injury. kidneys having a smooth outline are listed in Quite often CT suggests a laceration only indi- Table 10.2. It is difficult in an older patient to rectly if a follow-up scan reveals an increasing determine if a small kidney is secondary perinephric hematoma. to congenital hypoplasia or dysplasia or is due to an acquired condition such as ischemia or infection. Therapy Hypotension results in an increasingly dense and persisting bilateral nephrogram postcon- A rather conservative therapeutic approach is trast in kidneys that appear smaller than usual. evolving for CT-detected renal trauma in stable A similar but unilateral nephrogram occurs patients. For similar injuries some urologists with urinary tract obstruction and acute renal favor exploration while others manage them vein thrombosis. conservatively as long as the patient is hemody- Conditions leading to an enlarged kidney are namically stable. When contemplating nephrec- limited (Table 10.3). Diffuse tumor infiltration tomy versus conservative therapy of a damaged results in a poorly defined border between kidney, a postcontrast CT finding of enhancing tumor and normal parenchyma, making detec- parenchymal rim, even if thin, and excretion of tion difficult. A reniform shape is generally contrast into calyces should suggest a more preserved. In children, the most common cause conservative approach. Percutaneous interven- of bilateral enlarged kidneys is leukemic tional techniques suffice for some compli- infiltration. 591

KIDNEYS AND URETERS

Table 10.2. Conditions associated with a small, smooth ommended that the term acute pyelonephritis kidney(s) be adopted for this condition and this term is Congenital causes used here. Two complementary but distinct Dysplasia definitions are available for acute pyelonephri- Hypoplasia tis: a clinical one and a pathologic finding. Prune belly syndrome (Eagle-Barrett syndrome) Most acute pyelonephritis is secondary to Laurence-Moon-Biedl syndrome (?) an ascending infection. The less common Sequelae of multicystic dysplasia hematogenous source of acute pyelonephritis Alport’s syndrome often results in a different appearance from that Infection/inflammation seen in a setting of reflux; the inflammation ini- Chronic pyelonephritis tially is not lobar in distribution; rather, multi- Chronic glomerulonephritis ple foci of involvement predominate in the renal Post-infection or obstruction periphery. Eventually, however, most inflamma- Radiation (late) tions become confluent, and their appearance is Papillary or cortical necrosis similar regardless of origin. Pathologically, a focal involved segment is Medullary cystic disease sharply demarcated from adjacent normal Amyloidosis (late stage) parenchyma.In some,tissue necrosis progresses to frank abscess and, with a severe-enough Lead poisoning inflammation, the extrarenal space becomes Hemophilia involved. Chronic vesicoureteral reflux Diabetes (late stage) Collagen vascular disorders Table 10.3. Enlarged kidney(s) Vascular causes Congenital causes Associated with hypertension Dysplasia Renal artery stenosis (Poly)cystic disease Nephroptosis Hemihypertrophy Dissection Trauma Ischemia Arterial Urinary obstruction Emboli Infection/inflammation Thrombosis Acute pyelonephritis Chronic renal vein thrombosis Acute glomerulonephritis Hypotension Acute interstitial nephritis Nephrosclerosis Abscess Chronic infection Diffuse infiltration Neoplasia Amyloidosis (initially) Infection/Inflammation Sarcoidosis Lymphangiectasia Acute Pyelonephritis Acute tubular necrosis There is no uniform agreement on how to Diabetes (initially) describe an acute bacterial infection of the Nephrotic syndrome kidney.Such terms as acute pyelonephritis,acute Vascular causes bacterial nephritis, lobar nephritis, and lobar Acute renal vein occlusion nephronia abound in the literature and are often Hemolytic-uremic syndrome applied haphazardly. In addition, some patients Sickle cell disease have a pyelitis only, with relative parenchymal Transplanted kidney sparing. The Society of Uroradiology has rec- 592

ADVANCED IMAGING OF THE ABDOMEN

Most treated acute pyelonephritis leads to no tomography is also normal in a minority of sequelae. A minority of patients develop corti- these children. cal scarring, which is detectable with scintigra- Ultrasonography reveals a hyperechoic renal phy or urography. Renal insufficiency is rare; sinus in some children with in acute pyelon- perhaps more common is renal hypertension. ephritis (27), yet both US and power Doppler US findings range from normal to focal or multifo- cal defects, and normal US does not exclude Children parenchymal damage; even Doppler US under- Clinical estimates the extent of involvement. In children, Tc-99m-DMSA scintigraphy is Especially in children, it is reasonable to ascribe more sensitive in detecting pyelonephritis than acute pyelonephritis to vesicoureteral reflux is US or IV urography and appears to be even and retrograde introduction of bacteria. The more sensitive than CT and is preferred in problem is that in children with acute detecting and following renal damage due to pyelonephritis only about half are shown to acute urinary tract infection. While planar have reflux, while reflux is even less common in DMSA scintigraphy does detect renal cortical adults. Both vesicoureteral reflux frequency and defects, DMSA-SPECT detects more and is grade progressively decrease with age. preferred. Tc-99m-DMSA scintigraphy reveals End-stage renal disease secondary to postin- parenchymal findings suggestive of pyelon- fectious nephropathy probably occurs only after ephritis in a majority. In some, DMSA scintig- pyelonephritis, rather than after such urinary raphy simply shows swollen kidneys, with tract infections as cystitis. There is thus a need swelling obscuring the focal defects. Never- for a reliable test to detect pyelonephritis, theless, although a high sensitivity is achieved especially in young children where a clinical in detecting pyelonephritic cortical damage, diagnosis is difficult. scintigraphy cannot exclude the diagnosis. Because congenital urinary tract anomalies Tc-99m-MAG3 and Tc-99m-glucoheptonate are not uncommon in children with a urinary are also used to evaluate pyelonephritis in chil- tract infection, the underlying anatomy needs to dren. Using a mild (grade 1), moderate (grade be studied. Especially in young children, vesi- 2), and marked (grade 3) scale to grade the coureteral reflux is common in association with severity of decreased radionuclide localization, acute pyelonephritis, and thus voiding cys- MAG3 studies were able to detect 79% of grade tourethrography (or in some centers radionu- 2 and 96% of grade 3 cortical lesions but only clide cystography) appears reasonable.After the 59% of grade 1 lesions compared with Tc-99m- age of 9 to 10 years or so, reflux in association glucoheptonate scans (28). with acute pyelonephritis is sufficiently uncom- In a study of children with fever-producing mon that a need for voiding cystourethrography urinary tract infection, gadolinium-enhanced is individualized. MRI detected more pyelonephritic foci than Tc- 99m-DMSA cortical scintigraphy (29). The role Imaging of MR in this setting is still evolving. Neither an IV urogram nor US is sufficiently sensitive to serve as a screening test for Adults pyelonephritis in children. Most urograms Clinical during an acute attack are normal. In some chil- dren considerable time elapses before sufficient An unusual organisms, Mycoplasma hominis,is renal damage develops to be visible with urog- occasionally implicated in acute pyelonephritis. raphy. In a minority, the involved kidney is It should be considered if the patient does not enlarged and a delay and decreased contrast improve with conventional antibiotic therapy concentration are evident. The affected kidney and no organism is identified; special urine cul- returns to normal size in a week or so after the tures are necessary to grow this organism. start of treatment. Urography is normally per- Renal vein thrombosis, a common complica- formed primarily to detect other associated tion of acute pyelonephritis in the preantibiotic conditions, such as obstruction. Computed era, currently is rarely encountered. 593

KIDNEYS AND URETERS

One approach is to treat patients with sus- hyperdense appearance. In general, the CT pected uncomplicated acute pyelonephritis findings do not change clinical management. medically for 72 hours, and limit imaging Perinephric inflammation is evident with some only to those who do not respond or respond infections, and CT reveals thickening of Gerota’s poorly. Diabetics and other high-risk patients fascia and stranding in the perinephric fat. should undergo imaging early in the course of With a hematogenous origin, instead of infection. wedge-shaped defects, more numerous rounded low-attenuation parenchymal defects predomi- Imaging nate. An occasional patient develops a focal intraparenchymal homogeneous tumor mim- Imaging has a limited role during most episodes icking a neoplasm without other parenchymal of clinical acute pyelonephritis in adults; in or perirenal abnormalities. many patients no imaging abnormality is found, Ultrasonography identifies hydronephrosis, yet imaging is often obtained—not to detect but is relatively insensitive in detecting renal infection, but rather in a search for underlying parenchymal inflammation. A majority of congenital abnormalities that predispose to pyelonephritic kidneys appear normal. With a infection and detect any obstruction, stasis, severe inflammation, US identifies hypo- to calculi, or focus of infection. isoechoic and occasionally even hyperechoic Intravenous urography appears indicated regions. The latter presumably represent in diabetics, patients not responding to anti- hemorrhage. Compared to transabdominal US, biotics within 72 hours, and in a setting of an Doppler US appears to improve the detection of unusual organism. Suspected progression to acute pyelonephritis, although it probably is not an abscess or other complication warrants CT. as sensitive as CT. A percutaneous nephrostomy is indicated Because of cost and restricted availabil- with the presence of an obstructed collecting ity, MRI currently plays a limited role in most system. patients with suspected acute pyelonephri- The kidneys increase in size during acute tis. During an acute attack the kidney is pyelonephritis. In some adults focal swelling hypointense on T1- and hyperintense on T2- and decreased attenuation persists for months. weighted images. If pyelonephritis is severe enough, both in chil- Tc-99m-DMSA renal scintigraphy either dren and adults the final end point is focal scar- reveals a normal scan or identifies cortical ring of the affected lobe. defects; in a setting of acute pyelonephritis, Mild acute pyelonephritis does not result in scintigraphy appears to be more sensitive than any specific CT findings. Either focal swelling or IV urography or US. enlargement of the entire kidney develops with more severe involvement. Precontrast images occasionally show hypodense or hyperdense regions compared to normal parenchyma, with Emphysematous Pyelonephritis increased attenuation probably representing Clinical focal hemorrhage. Postcontrast CT in some patients reveals perfusion defects extending Emphysematous pyelonephritis is not a separate from the papilla to the periphery. At times entity, but a severe type of necrotizing the involved parenchyma exhibits near-water pyelonephritis. The criteria for defining this density, or delayed postcontrast scans show condition are not settled; some authors define enhancement of involved segments. emphysematous pyelonephritis only if gas is Computed tomography detects postcon- found within renal parenchyma, while others trast renal perfusion defects in up to two expand the definition and include gas not only thirds of patients with acute pyelonephritis, within the parenchyma but also in the excretory depending on the severity of infection. These system and perirenal spaces. Emphysematous defects range from unilateral to multifocal pyelonephritis should be differentiated from and bilateral.The temporal findings are not con- emphysematous pyelitis; the latter is a generally stant and can change rapidly. Thus a hypodense benign condition consisting of gas in the heterogeneous region can evolve into a streaky, urinary collecting system. 594

ADVANCED IMAGING OF THE ABDOMEN

Emphysematous pyelonephritis develops ence of streaky or mottled gas, or it contains mostly in diabetic patients, both insulin and either renal or perirenal fluid and bubbly or non–insulin dependent. Concomitant urinary loculated gas or collecting system gas. Such dif- obstruction is more common in nondiabetics. It ferentiation appears to be of prognostic impor- is a rapidly progressive, life-threatening infec- tance because the former patients have a more tion associated with gas-forming coliform bac- fulminant course. teria such as Escherichia coli and others. It is almost always unilateral. The simultaneous Therapy occurrence of emphysematous pyelonephritis and emphysematous cholecystitis is rare. Although some of these patients respond to Gas is located in the renal parenchyma, medical management,many undergo a nephrec- perirenal tissues, and at times the collecting tomy. Some have been successfully treated with system. imaging-guided percutaneous drainage, but such drainage is not feasible with diffuse involvement. Some drained patients subse- Imaging quently require elective nephrectomy for ade- In spite of some authors’ opinion that a diagno- quate therapy. sis of emphysematous pyelonephritis should be The serum creatinine level is the most reliable made by CT, quite often conventional radiogra- predictor of outcome. Affected kidneys tend to phy is sufficient to detect this condition. Thus in recover function after medical therapy,although patients with emphysematous pyelonephritis many of these patients with underlying diabetes diagnosed by CT, abnormal gas was identified already suffer from chronic renal failure. with conventional radiography in 66% and US in 88% (30). When localized, emphysematous Abscess pyelonephritis can mimic an abscess (Fig. 10.6). Emphysematous pyelonephritis generally is The term renal carbuncle is used by some radi- not associated with ureteral obstruction. ologists; it has no specific imaging definition The imaging appearance of emphysematous and some use it as a synonym for renal abscess. pyelonephritis consists of either parenchymal The term is probably best avoided in describing destruction with absence of fluid or the pres- imaging findings.

A B

Figure 10.6. Emphysematous pyelitis. A: Ultrasonography in a woman with cirrhosis and portal hypertension reveals hyperechoic structures with distal shadowing (arrows) in the right kidney. B: Transverse postcontrast CT identifies a gas-fluid level in a dilated calix (arrow). Follow-up CT 3 weeks after therapy revealed a normal appearing right kidney. (Source: Roy C, Pfleger DD,Tuchmann C, Lang HH, Saussine CC, Jacqmin D. Emphysematous pyelitis: findings in five patients. Radiology 2001;218:647–650, with permission from the Radiological Society of North America.) 595

KIDNEYS AND URETERS

At times acute pyelonephritis progresses to The imaging differential for most intrarenal scattered small abscesses, which eventually coa- abscesses includes a hemorrhagic or infected lesce into a gross abscess. The involved kidney cyst and a cystic neoplasm. is often enlarged.An abscess tends to be sharply marginated and has a rim of contrast enhance- Pyonephrosis ment. A subcapsular abscess displaces and compresses the adjacent renal parenchyma. Pyonephrosis defines an obstructed and Gas within an abscess is not common. Some infected renal collecting system. Invariably renal abscesses are associated with extrarenal renal parenchymal damage due to acute abscesses in adjacent structures. pyelonephritis is also present. Clinically these In general, CT detects renal and extrarenal patients range from being asymptomatic to abscesses better than US (Fig. 10.7). Still, US being in septic shock. Stones account for most detects the larger abscesses and often is more distal obstructions. Pyonephrosis is not clini- readily available in monitoring resolution. cally evident in some and only an obstructed Ultrasonography of an abscess identifies a urinary tract is suspected until aspiration pro- complex, thick-walled, cystic, fluid-containing vides the diagnosis. mass. Abscesses tend to be hypoechoic or ane- In a rare patient infection leads to gas within choic. With maturity the abscess outline be- the excretory system, called emphysematous comes better defined. pyelitis. This condition must be differentiated Gadolinium-enhanced MRI reveals renal from bladder reflux, recent instrumentation, abscesses as heterogeneous hypointense or a bowel fistula, conditions that can also intro- tumors; perinephric inflammatory stranding is duce gas into the renal excretory system. common. The MRI findings are similar to those The affected kidney usually shows little or no seen with contrast-enhanced CT,and in patients function. Urine in pyonephrosis tends to have who should not receive iodinated contrast, MRI increased CT attenuation. At times gray-scale is a viable alternative. US detects hyperechoic debris or gas, although An abnormal scintigram showing photopenic in many patients only hydronephrosis is found. regions in the kidney is nonspecific and does An occasional pyonephrosis ruptures and not differentiate between inflammation and results in a perinephric abscess. Even rarer is for abscess. such rupture to result in generalized peritonitis. Fungal Infection Urinary fungal infections are encountered with increasing frequency both because of the wider use of broad-spectrum antibiotics and an increasing number of immunocompro- mised patients. The most common organism is Candida albicans, followed by Tor ulopsis glabrata. Some fungal infections develop bilaterally. Most renal candidiasis occurs in a setting of systemic involvement. Typically numerous abscesses are scattered throughout the kidneys, similar to bacterial infections. Occasionally col- lecting system involvement results in a fungus ball, an appearance similar to an intraluminal tumor, but a fungus ball moves with a change in patient position and can even obstruct outflow. Figure 10.7. Right renal abscess.Contrast-enhanced CT reveals Fungus balls tend to be heterogeneous and a huge fluid-filled structure at the superior pole of the right hypodense, with no contrast enhancement, kidney (arrows). It was drained percutaneously. (Courtesy of while US reveals a hyperechoic tumor with no Patrick Fultz, M.D., University of Rochester.) posterior acoustic shadowing (31). 596

ADVANCED IMAGING OF THE ABDOMEN

Tuberculosis sive fibrosis leads to foreshortening. Ureteral calcifications are uncommon, thus aiding in Most urinary tuberculosis is due to hematoge- distinguishing tuberculosis from the more nous spread. At times the primary site is not common ureteral calcifications found in identified, although active or inactive lung schistosomiasis. disease is found in a majority.Although initially Some patients with bladder trigone involve- both kidneys are infected, disease often pro- ment develop upper tract obstruction and gresses unilaterally. eventually renal function is lost even if the Among 57 patients with urogenital tubercu- obstruction is relieved by stenting or a percuta- losis, fever, anorexia, and weight loss were neous nephrostomy; a kidney can deteriorate evident only in 11%, 16% had an isolated genital from an acceptable pretherapy glomerular lesion, and, surprisingly, 14% presented with filtration rate to becoming nonfunctional after renal failure (32); bacilluria was identified only relief of an obstruction. Predictors of renal in 5%. These patients have a sterile pyuria, recovery after diversion are an adequate resid- microscopic hematuria, and an acidic urine. The ual renal cortex and a glomerular filtration rate diagnosis is confirmed by urine culture, a pro- of >15mL/min. cedure taking up to 4 weeks.At times US-guided At the more advanced stages CT and urogra- aspiration is helpful in establishing the diagno- phy should suggest the diagnosis. In some pa- sis. A polymerase chain reaction to detect tients xanthogranulomatous pyelonephritis is in mycobacterial DNA has a high sensitivity and the differential. At times a tuberculous kidney establishes the diagnosis. develops a fistula to an adjacent organ. Urography was abnormal in 80% of affected individuals, with the most frequent abnormality Schistosomiasis being a nonfunctioning silent kidney found in 40% (32). Schistosomiasis generally affects the lower Focal infections, or tuberculomas, develop portion of both ureters. Involvement is usually initially. Tuberculomas tend to be hypointense bilateral and results in stenosis and a thickened on both T1- and T2-weighted MRI, provided ureteral wall. Often multiple strictures are they contain no calcifications, hemorrhage, or evident and proximal ureteral dilation develops. fibrosis. These either resolve spontaneously or Early in the course a contrast study often reveals enlarge, become necrotic, and communicate soft tissue polyps. Calcifications develop with with the collecting system, spreading infection chronic infection and have a characteristic distally. Imaging at this stage reveals irregular, linear appearance; a diagnosis of schistoso- necrotic, and moth-eaten papilla, at times miasis can be strongly suggested if such mimicking papillary necrosis due to other calcifications are seen in a young adult from causes. Some calyces become obstructed due to endemic regions. infundibular stenosis. Strictures range in loca- Curiously, in distinction to bladder involve- tion from calyces to ureters, leading to obstruc- ment, ureteral schistosomiasis is not associated tion and further damage. Cortical scarring, with a high risk of ureter cancer. calyceal distortion, and strictures with caliecta- sis develop. In some, CT simply identifies small Echinococcal Cyst hypodense tumors along the renal cortex (33). Ulcerations, abscesses, and fibrosis dominate Although uncommon, hydatid cysts do occur in the late stages of infection. Extension of infec- the kidneys,with Echinococcus granulosus being tion outside the kidney leads to perinephric more common than Echinococcus multilocu- abscesses. Calcifications vary from curvilinear laris. In rare instances renal cysts develop bilat- to diffuse, from homogeneous to granular. If erally. Ureteral cysts are rare. No age group is neglected, eventually the small, calcified kidney immune, including children. loses all function. Patients are often asymptomatic until the Ureteral involvement results in a shaggy, pressure on an adjacent structure or cyst irregular lumen. A dilated ureter ensues with rupture develops. Rupture into a collecting ureterovesical junction obstruction. In time, the system leads to hydatiduria and possible renal ureter wall thickens, ulcers develop, and exten- colic due to cyst debris. 597

KIDNEYS AND URETERS

Percutaneous needle aspiration tends to be non- diagnostic. Some patients require several explo- rations and numerous intraoperative biopsies to establish a correct diagnosis. Similar to other sites, renal actinomycosis often progresses to extensive fistulas, including renoenteric fistulas. This chronic infection is a cause of retroperitoneal fibrosis and obstructive uropathy.

Botryomycosis Botryomycosis, or a chronic bacterial infection consisting histologically of abscesses containing bacteria-bearing granules, is rare in the kidney. Figure 10.8. Primary renal hydatid disease. Unenhanced CT Most often Staphylococcus aureus is involved. reveals a hypodense tumor in the left kidney.Peripheral daugh- The imaging appearance in some patients ter cysts and calcifications are evident. (Source: Polat P,Kantarci mimics a renal cell carcinoma. The diagnosis M, Alper F, Suma S, Koruyucu MB, Okur A. Hydatid disease from consists of detecting aggregates of organisms in head to toe. RadioGraphics 2003;23:475–494, with permission from the Radiological Society of North America.) sulfur-like granules within an abscess or urine. These granules should not be confused with actinomycosis.

Extensive cyst wall calcifications are Leishmaniasis common. A typical appearance is a calcified tumor compressing the pelvicalyceal system or Infestation with protozoan parasites of the ureter, at times identified even with conven- genus Leishmania ranges from cutaneous tional radiography. Similar to the liver, some lesions to fatal systemic involvement. In cysts contain mural nodules (Fig. 10.8). The southern France, Leishmania infantum is presence of a solid component within a cyst endemic, is carried by sand flies, and causes mimics a renal cell carcinoma. At times “sand” infantile leishmaniasis (Mediterranean visceral is detected in the dependent portion of a cyst. leishmaniasis). Daughter cysts lead to a multiloculated appear- Leishmaniasis of the genitourinary tract is ance. In time, calcified daughter cysts result in rare. Its imaging appearance mimics pyonep- a cysts-within-a-cyst appearance, a finding sug- hrosis caused by more common organisms. gesting the diagnosis. Most hydatid cysts have mixed echogenicity on US. Filariasis As in the liver, percutaneous drainage of renal hydatid cysts is a therapeutic option. Chyluria, or white urine, is a complication of filarial infection, found most often in tropical regions. It is probably due to focal lymphatic Brucellosis rupture into collecting systems. In temperate climates chyluria is due to retroperitoneal Brucellosis is rare in the kidney. These infec- malignancy, trauma, or chronic infection result- tions range from acute focal brucella nephritis, ing in lymphatic obstruction. to a focal brucelloma, to diffuse. All ages are Pedal lymphoscintigraphy using Tc-99m– affected. sulfur colloid detects retrograde lymph flow into the kidneys. Actinomycosis Chyluria due to filariasis was successfully treated by endoscopic coagulation of suspected Renal actinomycosis is readily confused with rupture sites, most often in a caliceal fornix a malignancy, leading to a nephrectomy. (34). 598

ADVANCED IMAGING OF THE ABDOMEN

Viral Infection Problems arise in detecting progression of renal damage. Neither IV urography nor US nor Hantavirus infection leads to an interstitial scintigraphy provides an accurate quantitative hemorrhagic nephritis, occasionally progress- assessment of residual normal renal tissue. ing to acute tubular necrosis (discussed in a Computed tomography and probably MR can later section). Some evidence suggests that Han- measure remaining renal parenchymal volume tavirus infection is a risk factor for subsequent and thus provide prognostic data. renal hypertension. Xanthogranulomatous Chronic Pyelonephritis Pyelonephritis (Nephropathy) Xanthogranulomatous pyelonephritis is an Chronic pyelonephritis is not a single disease atypical, chronic renal inflammation often pro- but rather a convenient description of a number gressing to parenchymal destruction. It ranges of related entities. Pathologists tend to sub- from focal, where it mimics a neoplasm, to divide chronic pyelonephritis into interstitial diffuse, but bilateral involvement is uncommon. and granulomatous varieties, with the latter With some, fistulas develop into surrounding including such entities as xanthogranulomat- structures, including the colon (35). It can ous pyelonephritis, malacoplakia, and renal evolve into an adjoining abscess. The involved tuberculosis. kidney enlarges and either functions poorly An association between vesicoureteral reflux, or is nonfunctioning. Women are more often urinary tract infection, and subsequent renal affected; it occurs in children, where this damage is well known, with such terms as reflux diagnosis is often not considered.In fact,in chil- nephropathy and postinfectious nephropathy dren xanthogranulomatous pyelonephritis and applied to this condition. If unchecked, renal resultant end-stage pyelonephritis are not un- injury has the potential to progress to overt end- common causes for a nephrectomy. stage renal failure. Histology reveals an inflammatory infiltrate Vesicoureteral reflux in children progressing containing large lipid-filled macrophages (xan- to intrarenal reflux leads to renal damage thoma cells), fibrosis, and fat necrosis if the (intrarenal reflux implies reflux into ducts of perirenal fat is involved. An uncommon associ- Bellini). Reflux into collecting tubules is more ation is with an underlying malignancy. common in compound papillae, which in turn A common clinical presentation is anemia, are more often located in the renal poles. leukocytosis, and flank pain. A majority of Thus intrarenal reflux and clinical chronic patients have urinary obstruction due to pyelonephritis progress to loss of renal nephrolithiasis, at times even a staghorn calcu- parenchyma, typically at the renal poles, mani- lus. Urography and US reveal calculi, hydro- festing with imaging as renal scarring. Scarring nephrosis, or a renal tumor, findings that are results in inhomogeneous contrast enhance- nonspecific. Computed tomography findings ment and is also detected with DMSA scintigra- include renal enlargement, usually the presence phy. With progression, scarring eventually of a calculus, scattered hypodense regions rep- evolves into small, lobulated kidneys, distorted resenting obstructed calyces and other fluid- and clubbed calyces, and renal cortical juxta- filled cavities, and, at times, extrarenal phle- papillary scarring, findings that are readily gmon extension. Chemical-shift MR aids in detected, although whether a small kidney detecting fat. The kidney does not function with is secondary to chronic damage due to vesi- diffuse involvement. Inflamed tissue surround- coureteral reflux or whether it represents con- ing a cavity often enhances with contrast. An genital renal hypoplasia cannot be ascertained. occasional fistula develops, including a With enough loss of renal function, a nonin- renocolic fistula. volved contralateral kidney becomes hyper- A minority of patients present with a tumoral trophic. At times normal residual parenchyma form mimicking renal carcinoma, with imaging in a focally diseased kidney also undergoes often suggesting a neoplasm, and even produc- compensatory hypertrophy. ing a vena cava thrombus.A biopsy is often nec- 599

KIDNEYS AND URETERS essary to establish a diagnosis. In general, many unusual and often consist of ureteral obstruc- of these patients eventually undergo a nephrec- tion. Because tissue manipulation tends to exag- tomy. There can be, however, total renal recov- gerate fibrosis, surgery should be avoided in ery on antibiotic therapy alone. these patients and obstruction treated with an endoprosthesis, if possible. One patient with long-standing extraperi- Malacoplakia toneal Erdheim-Chester disease developed renal arteries stenosis, bilateral ureteral stenosis, and Malacoplakia is an uncommon chronic an adhesive capsulitis (36). inflammatory condition (chronic tubulointer- stitial nephritis) characterized by round intra- and extracellular inclusions known as Sjögren’s Syndrome Michaelis-Gutmann bodies. Histology reveals Renal involvement is subclinical in many large, foamy, granular macrophages with eccen- Sjögren’s patients. Yet the reverse is also true; tric nuclei and prominent nucleoli containing at times renal involvement, including severe laminated inclusions. Macrophage dysfunction hypokalemia, is the initial manifestation of appears to be the underlying pathogenesis. Its Sjögren’s syndrome.When present, it most often relationship to xanthogranulomatous pyelonep- manifests as a tubulointerstitial nephritis or hritis remains conjecture. renal tubular acidosis and stone disease, includ- Malacoplakia affects a number of organs, ing nephrolithiasis and nephrocalcinosis. with the urinary tract being the most common An inflammatory tumor develops occasion- site. It develops in debilitated and immunocom- ally. These tumors tend to be heterogeneous and promised patients.Some patients have had renal hypodense with CT and hyperechoic with US. transplants. It is more common in women. Differential diagnosis for such a tumor includes Ureteral involvement is less common than renal. infection, infarction, and a malignancy. Occasionally it develops bilaterally. Recurrent E. coli infection is often detected. Inflammation tends to spread to adjacent structures. Needle Sinus Lipomatosis biopsy is often diagnostic. At times a portion or almost the entire kidney Contrast CT identifies variable enhancement is replaced by fat, most often unilaterally, called of a soft tissue or partly cystic tumor or multi- replacement lipomatosis. Rarely, perirenal or ple tumors. Calcifications are not a feature of even periureteral tissues are also involved. this condition. Hydronephrosis develops with Many of these patients have a long history of extensive ureteral involvement. chronic infection, calculi, and renal atrophy. An Gallium-67-citrate scintigraphy reveals renal obstructing calculus is identified in some, and uptake; serial Ga-67 scanning identifies these kidneys often have decreased function decreased uptake or complete resolution after or are nonfunctioning. Xanthogranulomatous antibiotic therapy, and this test appears useful pyelonephritis, in particular, is often associated in establishing an end point to therapy. with lipomatosis, yet these are two distinct When extensive, malacoplakia mimics a entities. Little evidence suggests a neoplastic neoplasm, inflammation, or even ureteritis association. cystica. An occasional scenario is that imaging Histology reveals renal parenchymal atrophy detects a ureteral tumor, a carcinoma is sus- and extensive replacement lipomatosis, in dis- pected,and a nephroureterectomy is performed; tinction to the large lipid-filled infiltrating malacoplakia is diagnosed only on histologic macrophages found in xanthogranulomatous examination of the resected specimen. pyelonephritis The involved kidney enlarges. Renal sinus Erdheim-Chester Disease fat is exaggerated and replaces atrophied parenchyma. This extensive fat deposition is Erdheim-Chester disease, an uncommon sys- identified by CT and US and aids in differenti- temic histiocytosis, is discussed in more detail ating replacement lipomatosis from the infiltra- in Chapter 14.Although retroperitoneal involve- tive xanthogranulomatous pyelonephritis. At ment is common, perirenal complications are times the overall appearance suggests a fat- 600

ADVANCED IMAGING OF THE ABDOMEN containing neoplasm, but the latter generally Hypervascular tumors are generally cancers but results in little parenchymal atrophy. hypovascular tumors include cancers, adeno- mas, angiomyolipomas and even an occasional hemorrhagic cyst. Tumors Phase-inversion tissue harmonic imaging is superior to B-mode US in study of focal kidney The Indeterminate Renal Tumor lesions (37); it achieves greater image quality, lesion conspicuity and better fluid-solid differ- Wide use of imaging techniques has led to a rise entiation than B-mode US. in the number of incidentally detected renal A renal tumor believed to contain a cystic tumors. Although many are not associated with component is best approached with US; many of any clinical signs and symptoms and although these are identified as simple cysts. Complex most are shown to be simple renal cysts, a cysts, however, are indeterminate with US and number are neoplastic and thus present a diag- require further evaluation. Contrast CT, and nostic dilemma. Imaging classification of some lately MRI, are preferred for a tumor containing of these is straightforward, but others are inde- a solid component. If needed, scintigraphy terminate in their appearance. In particular, using a cortical imaging agent distinguishes tumors <1cm in diameter are difficult to char- functioning renal tissue from nonfunctioning acterize by imaging, and the literature provides neoplasms. If the tumor is still indeterminate, little guidance about their management. Initial biopsy provides a histopathologic diagnosis annual imaging appears reasonable to establish for most but not all solid tumors, although whether growth occurs, but such an approach is with current imaging few indeterminate renal based more on intuition than on any hard data. tumors need a biopsy. In the very young, the very old, and those with Among renal tumors suspicious for being a limited life expectancy, an argument can be malignant on CT, a majority appear heteroge- made for watchful waiting. Imaging and possi- neous on T2-weighted images and enhance on ble therapy of a small indeterminate renal dynamic MRI. An occasional one does not tumor in a young adult poses a dilemma; if US enhance, primarily due to hemorrhage, but even is nondiagnostic for a simple cyst, an argument these tend to be heterogeneous on T2-weighted can be made for CT follow-up and resection images (38). only if it grows. The role of 2-[18F]-fluoro-deoxy-D-glucose In general,CT and MR can readily distinguish (FDG)-PET in evaluating indeterminate renal between a benign cyst and a malignancy. More cysts is not defined, and currently insufficient problematic is differentiating solid tumors—a evidence exists to suggest it for the study of renal cell adenoma, carcinoma, oncocytoma, indeterminate renal tumors. metastasis, lymphoma, and other less common tumors tend to have a similar appearance. The differential diagnosis often also includes Nonneoplastic inflammatory conditions, some hemorrhagic or Ectopic Splenic Tissue infected renal cysts, abscesses, and some vascu- lar abnormalities. Imaging often cannot reliably Ectopic splenic tissue within the kidney can distinguish between these conditions, with the mimic a solid tumor.A radionuclide spleen scan exception of angiomyolipomas. A small but should suggest the diagnosis. heterogeneous tumor generally represents a cancer, keeping in mind that CT shows some Lobar Dysmorphism cancers to be homogeneous. At times CT sug- gests focal inflammation in a solid tumor by Renal lobar dysmorphism is a normal develop- detecting peripheral rim contrast enhancement. mental variant that simulates a renal tumor. Perinephric infiltration is found with both Some are detected incidentally by imaging.They inflammatory conditions and lymphomas. range from intrarenal to peripelvic in location. Most cancers tend to be hypoechoic on US; Contrast CT can suggest the diagnosis; during hyperechoic tumors range from angiomyolipo- the corticomedullary phase the oval-shaped mas, some cancers and an occasional adenoma. lobar dysmorphism is detected in the perihilar 601

KIDNEYS AND URETERS medulla, while the nephrogram phase reveals Intravenous urography and CT identify an accumulation of contrast within pyramids. intraluminal polyp. Some of these tumors are rather large and fill almost the entire renal Inflammatory Pseudotumor pelvis. These polyps are a cause of ureter obstruction and the resultant hydronephrosis. Inflammatory pseudotumors, of controversial An occasional one is cystic and contains septa. pathogenesis, are rare in the kidneys or ureters Ureteral fibroepithelial polyps tend to mimic (this condition is discussed in Chapter 14). transitional cell carcinoma. The radiographic Imaging identifies a soft tissue tumor. and ureteroscopic appearance of a ureteral rhabdomyosarcoma suggested a benign Rosai-Dorfman Disease (Sinus Histiocytosis) fibroepithelial polyp (40). A rare benign entity first described in 1969, Rosai-Dorfman disease consists of sinus his- Vascular Tumors tiocytosis with massive lymphadenopathy, Arteriovenous Malformation although several patients with bilateral renal infiltration by inflammatory cells, including his- Arteriovenous malformations develop in both tiocytes, and without adenopathy, have been the kidneys and the ureters. They are a cause of described. hematuria, which at times is massive. Ultrasonography in one patient revealed Imaging findings of some renal arteriovenous large, heterogeneous hypoechoic renal tumors malformations are similar to those of renal cell containing calcifications (39); postcontrast CT carcinomas. Some renal arteriovenous malfor- showed less homogeneous tumor enhancement mations are misdiagnosed with CT as a solid than renal parenchyma and no invasion,but col- tumor, suggesting a malignancy. lecting system distortion was evident. Hematuria due to an arteriovenous malfor- mation can generally be controlled by transar- terial embolization and ablation; hematuria Hamartoma can recur and these malformations are A cystic hamartoma of the renal pelvis is a rare amenable to retreatment; complications include tumor consisting of fibroblasts, smooth muscle, varying degrees of renal infarction, pulmonary and epithelial tissue. Some mesoblastic nephro- embolism, and renin-dependent hypertension. mas reported in the literature may represent cystic hamartomas. These cystic tumors Hemangioma develop adjacent to the renal pelvis and are detected by most imaging. Most renal hemangiomas occur as part of Angiomyolipomas are discussed later in this Sturge-Weber syndrome or Klippel-Trénaunay chapter (see Mesenchymal Neoplasms). syndrome. They are not common. Both capillary and cavernous varieties occur, but cavernous ones are more common. Most renal heman- Fibroepithelial Polyp giomas are discovered incidentally, with an The benign fibroepithelial polyp contains occasional one manifesting by bleeding. epithelium and stromal tissue. Whether these Imaging usually suggests a solid renal tumor polyps represent a hamartoma or are part of a similar to a renal cell carcinoma. An occasional reactive postinflammatory process is debatable. one occurs at the renal hilum or even renal Most occur in the renal pelvis. Some develop a capsule. thick stalk covered by normal overlying transi- tional epithelium. Anecdotal reports describe Papillary Endothelial Hyperplasia multiple ureteral fibroepithelial polyps. They should be differentiated from papillomas, Precontrast CT of renal intravascular papillary which are neoplastic in origin. They are rare in endothelial hyperplasia (Masson’s tumor) children. revealed a 3-cm perirenal hypodense tumor, Clinically, these polyps bleed or the patient while dynamic CT identified peripheral enhan- presents with pain due to obstruction. cement during an early phase and homoge- 602

ADVANCED IMAGING OF THE ABDOMEN neous enhancement during delayed phase (41); Table 10.5. Bosniak system of classifying cystic renal masses the appearance mimicked a hemangioma. Category I Simple cyst Category II Mildly complicated but clearly benign Cystic Nonneoplastic Conditions Thin septa, few calcifications Category III More complicated cyst—indeterminate, Classification need histological diagnosis Some of the renal tumors having a cystic com- Thicker septa, multilocular, increased ponent detected with imaging are listed in Table density, more calcifications 10.4. Discussed in this section are the more Category IV Cystic neoplasm common cystic renal conditions. Cystic hamar- Thick walls, enhancing soft-tissue tomas have already been mentioned. Various component cystic neoplasms are covered later in their Source: Adapted from Bosniak (42). respective sections. The Bosniak system of classifying cystic renal masses is based on their CT appearance (Table 10.5). It is of practical use. Cysts in category II contain one to two thin septa; if in doubt, a cat- Table 10.4. Renal cystic tumors egory III cyst should be considered, which has a more complex gradation, is indeterminate, and Simple cyst many need a histologic diagnosis. About half Complex cyst or so of category III cysts are malignant. Solid Hemorrhagic cyst nodules in a cyst (category IV cyst) enhancing Infected cyst with contrast imply a malignancy. Aspiration is Dialysis acquired cysts indicated of cysts in category IV,and if the aspi- rate is bloody a neoplasm is likely. A chronic Congenital cystic disorders renal abscess is in the differential for a category Multicystic dysplasia Autosomal dominant polycystic disease IV cyst. A study of patients with cystic renal Autosomal recessive polycystic disease tumors from two teaching institutions found Glomerulocystic disease that all resected Bosniak category I and von Hippel-Lindau disease II tumors were benign and category IV tumors Tuberous sclerosis were malignant (43); on the other hand, 59% of Ehlers-Danlos syndrome category III tumors were malignant. Congenital megacalyces The Bosniak classification does have limita- Focal hydronephrosis tions; some minimally complex cystic renal tumors contain malignant cells; some malignant Calyceal diverticulum tumors in categories II and III have contrast Pyelogenic cyst enhancement of less than 10 HU. In general, cat- Urinoma egory II cysts are better evaluated with CT than US. Magnetic resonance imaging and renal Infection/inflammation angiography have a role in defining Bosniak cat- Papillary necrosis egory II and III cysts, but even here diagnostic Cystic renal pelvis hamartoma confidence is at times difficult, especially with smaller cystic tumors. Cystic neoplasms The Bosniak classification has been applied Multilocular cystic nephroma using MR imaging criteria. In general, CT and Cystic carcinoma MR imaging findings are similar, but in some Vascular causes cysts MR depicts additional septa, thicker cyst Aneurysm wall and septa, or different enhancement pat- Renal vein varices terns, resulting in upgrading of the Bosniak Arteriovenous malformations classification (44). Hematoma A primary imaging function both for cysts Hemangioma and solid tumors is to differentiate intrarenal 603

KIDNEYS AND URETERS from extrarenal ones, a task not always possible. in order: a renal cyst attenuation increase up to Capsular tumors are one example, yet at about 10HU postcontrast is often due to an arti- times even a retroperitoneal lesion adjacent fact from surrounding parenchymal enhance- to the kidney mimics an intrarenal neoplasm. ment (46). A rare mucinous cystadenoma originating in With gray-scale US a simple cyst should show retroperitoneal tissues can suggest a renal cyst. an anechoic lumen, well-defined walls, acoustic enhancement posterior to the cyst, and no as- sociated nodularity or wall thickening. Thin Simple Cyst septa may be identified, findings often not seen Clinical with CT. The differential diagnosis for a “simple Simple renal cysts are present in about 10% of cyst” detected by gray-scale US includes an the population. They are not common in chil- obstructed calyx, calyceal diverticulum, papil- dren but increase in size and number with age. lary necrosis, an aneurysm, and a vascular Their pathogenesis is unknown. Most simple tumor. A pseudoaneurysm mimics a cyst on cysts are solitary, unilocular, and located in the gray-scale US, and Doppler US is necessary to cortex, with the more central ones known as differentiate between them; Doppler US shows parapelvic cysts. Perinephric cysts are those no flow, thus excluding a vascular lesion (except located beneath the renal capsule. The terms a thrombosed one). parapelvic and perinephric cyst are useful to Similar to other nonflowing fluid of water describe a cyst’s location. Exoparenchymal cysts density, a simple cyst is hypointense or almost are larger and have a greater tendency to has a signal void on T1- and is hyperintense on increase in size than endoparenchymal cysts. T2-weighted MRI. It does not enhance postcon- Most simple cysts are detected incidentally. trast. The cyst wall should be imperceptible; Some larger ones are associated with hematuria otherwise a more complex cyst etiology should or flank pain. be suggested.

Imaging Therapy A simple cyst should have a sharp, well-defined A high recurrence rate is common after aspira- margin at its interface with normal renal tion of a simple cyst. Typical therapy consists of parenchyma. Simple cysts do not have thick percutaneous injection of a sclerosing agent, walls or prominent septa. Likewise, no associ- with repeat injection if a cyst recurs. Use of 95% ated soft tissue mass should be present. Many of to 98% alcohol is effective and leads to complete these cysts are defined by US, but any sugges- regression of most cysts, except those >10cm in tion of an associated solid component or wall diameter. One technique consists of catheter thickening requires CT, or, in some instances a insertion under US control, cyst drainage and biopsy. Some benign cysts have thin, linear sampling for bacteriologic and cytologic study, calcifications corresponding to the cyst wall or cyst opacification with contrast, instillation of septa. Any mottled or amorphous calcifications roughly half the cyst volume of ethanol, and should be viewed with suspicion. Septa in a clamping for 20 minutes. Some authors prefer benign cyst should be uniformly thin. two sequential sclerosing agent injections over Computed tomography attenuation of a a 48-hour period. Local infiltration or intravas- simple cyst should be that of water. A density cular injection results in lysis of cell membrane, greater than 10HU suggests a complex cyst. protein denaturation, local vascular occlusion, Higher densities are seen with hemorrhage into and cell death. a simple cyst. Infection results in a thickened Laparoscopic decortication of simple renal wall. Compared to an unenhanced density, the cysts is effective therapy for pain relief. Such attenuation coefficient of a cyst should increase therapy must be limited to Bosniak categories I by no more than 10HU during the corti- and II cysts with their low risk for cancer. comedullary and parenchymal phases (45). Any In an occasional hypertensive patient, greater enhancement or nodularity should raise drainage of a simple cyst corrects hypertension; suspicion for a malignancy. However, a caveat is rather than ascribe hypertension directly to the 604

ADVANCED IMAGING OF THE ABDOMEN cyst, it is more likely that the cyst had com- Delayed postcontrast CT is occasionally pressed and narrowed an adjacent renal artery. helpful in differentiating a homogeneous complex renal cyst from a neoplasm; those Parapelvic Cyst showing no change in attenuation between initial postcontrast and delayed CT are most Radiologists describe a cyst located in the renal consistent with a cyst, but cysts showing an sinus region, adjacent to renal pelvis, as a renal attenuation decrease suggest presence of vascu- sinus cyst or parapelvic cyst. Most are simple larity (47). cysts. Many of these cysts presumably form by Pre- and postcontrast MR is helpful in evalu- prior urine extravasation or are embryologic ating complex cysts, although the MR appear- lymphocysts. Most are detected as an incidental ance of benign and malignant complex cysts finding, but an occasional one compresses the overlaps. Cyst content varies considerably in adjacent renal pelvis sufficiently to produce intensity on precontrast T1- and T2-weighted some degree of obstruction. They vary in size, images due to different protein concentrations, and range from solitary to multiple and unilat- but cyst content should not enhance postcon- eral to bilateral. trast. In particular, a complex cysts containing a These cysts mimic a portion of the renal heterogeneous MR fluid signal intensity should collecting system on precontrast imaging and be viewed with suspicion for a malignancy. do not enhance on postcontrast CT. Delayed Cysts with an irregular, thick cyst wall or mural images postcontrast identify the lack of com- nodules tend to be malignant. munication with the urinary collecting system. An occasional cyst is more dense than renal At times US confuses a parapelvic cyst with parenchyma on precontrast CT. These hyper- hydronephrosis. An occasional one suggests a dense cysts contain old blood, milk of calcium, cystic neoplasm. or a similar component. In fact, a cyst may not be suspected because of the hyperdense CT Complex Cyst appearance; US should reveal their cystic nature. These cysts may contain internal echoes. While a complex cyst is a pathologic entity,radi- While some of these cysts may be followed seri- ologists use the term in a descriptive sense for ally, an occasional cystic renal carcinoma also a cyst containing blood, septa, a thick wall, or has a hyperdense CT appearance. calcifications. Complex cysts have thicker walls than simple cysts, better defined septations, a suggestion of nodularity, and calcifications Infected Cyst may develop, or they do not contain clear fluid. An infected cyst often develops a discrete, thick- Occasionally a fluid–fluid level develops in a ened wall. Gas or debris is part of the cyst cyst after a recent hemorrhage. Differentiation content in some. Septations develop in both from a simple cyst is one of gradation. Thus infected and hemorrhagic cysts. bleeding or infection in a simple cyst changes Most suspected infected cysts are drained cyst fluid composition and leads to wall thick- both for therapy and to exclude an underlying ening. From an imaging viewpoint, the major malignancy. importance of a complex cyst is its mimicry of a malignant cyst. The risk of a complex cyst being malignant Hemorrhagic Cyst increases with imaging findings of more complex structures; thus discrete cyst wall In adults, hemorrhage into a benign renal cyst thickening, irregular septations, or any nodular- is relatively common. It is rare in children. ity points toward a cystic malignancy, and aspi- Nevertheless, caution is required in ascribing ration of such a cyst serves little purpose; even hemorrhage to an underlying benign cyst; hem- if a benign aspirate is obtained, such a cyst orrhage also occurs into renal cell carcinomas, should be assumed to contain a malignant especially in patients with renal failure. component. Computed tomography of a hemorrhagic Increased fluid echogenicity is generally sec- cyst reveals a hyperdense cyst. Cyst content ondary to blood or infection. does not enhance postcontrast. Gray-scale US 605

KIDNEYS AND URETERS

shows increased internal echoes. If followed appear as multicystic tumors, peripelvic or per- serially, findings should regress with time. In an inephric in location. Rather than being cystic, at occasional hemorrhagic cyst both CT and US times diffuse perinephric fluid is identified.This suggest a solid tumor, and these cysts are gen- fluid is close to water density, except if tainted erally resected. by hemorrhage.Aside for an often more periph- T2-weighted MRI within days of hemorrhage eral location and perinephric fluid, imaging into a cyst reveals a hypointense signal. Later, findings tend to mimic multilocular cysts found hemorrhage results in a hyperintense signal in more common disorders. on both T1- and T2-weighted images. Some In some, lymphangiectasia is associated with hemorrhagic cysts contain a fluid–fluid level. A a preserved rim of renal cortex and decreased benign cyst should have a very thin wall. medullary attenuation. Ultrasonography reveals a hyperechoic kidney. Computed tomography Lymphangiectasia and US findings suggest the diagnosis (Fig. 10.9).Aspiration of chyle from perinephric fluid Renal lymphangiectasia (also called lymphan- should be diagnostic. giomatosis and lymphangiomas when cystic) is considered to be a lymphatic developmental Localized Cystic Disease malformation, although some authors believe inflammation and lymphatic blockage are incit- Localized cystic disease of the kidney is a ing factors while still others classify it as a mes- descriptive term for a condition that cannot be enchymal neoplasm. A rare familial association readily classified. These patients had unilateral is described. These cysts are lined by endothe- multiple cysts varying in size, separated by lial cells. They are rare in the kidneys. Most normal renal parenchyma, and contained in a affected patients are asymptomatic, but pain or larger nonneoplastic tumor (48). No family hematuria is an occasional presentation. A rare history of autosomal-dominant polycystic association is with renal vein thrombosis. kidney disease is found. Hematuria or flank Detected mostly in children and young pain is a usual presenting symptom. Imaging adults, renal lymphangiectasia is one of the reveals one or several cysts in a larger tumor, at causes of an enlarged kidney. Lymphangiomas times suggesting a cystic neoplasm.

A B

Figure 10.9. Renal lymphangiectasia. A,B: Transverse contrast-enhanced CT images show bilateral perirenal fluid (arrows), peripelvic fluid (arrowheads), and fluid around great vessels. Attenuation of the perinephric collections is less than 10HU (Source: Ramseyer LT.Case 34: renal lymphangiectasia.Radiology 2001;219:442–444,with permission from the Radiological Society of North America.) 606

ADVANCED IMAGING OF THE ABDOMEN

Renal Cell Adenoma and metastases at initial presentation. Classification of these carcinomas is incomplete. Renal Adenocarcinoma medullary carcinomas associated with sickle Throughout this book most benign and malig- cell trait (discussed later) are also collecting nant neoplasms are discussed as separate enti- duct neoplasms. ties, but such differentiation is impractical with One limitation of a morphologic classi- renal cell adenomas and carcinomas. Whether a fication as outlined above is the heterogeneity of renal adenoma is a separate and distinct entity some of these tumors. To overcome this, the or whether it is a premalignant version of a Heidelberg Classification of Renal Cell Tumors renal cell carcinoma is debatable. Indeed, patho- was developed in 1996, based on tumor genetic logic criteria defining a renal cell adenoma are properties correlated with their histologic not clear and while clinically a distinction is findings (50); this classification subdivides obviously desirable, both pathologically and renal cell tumors into benign and malignant radiologically the boundaries between renal cell parenchymal neoplasms. Benign tumors are adenomas and adenocarcinomas are blurred. further classified into metanephric adenomas Tumors smaller than about 3cm tend not to and adenofibromas, papillary renal cell adeno- metastasize, and some investigators believe mas, and oncocytomas. Malignant tumors are these represent mostly adenomas. From an classified into conventional renal cell adenocar- imaging viewpoint it appears best to discuss cinoma, papillary (chromophil) renal cell carci- these tumors as part of a spectrum. noma, chromophobe renal cell carcinoma, and The term hypernephroma is often used collecting duct carcinomas. Some of these synonymously for a renal adenocarcinoma. tumors cannot be readily classified. Others An older term, Grawitz tumor, is rarely represent separate entities. encountered. At times helical CT findings can suggest a particular subtype. Clear cell carcinomas have greater contrast enhancement than chromophil Classification (papillary), chromophobe and duct of Bellini carcinomas (51); chromophobe carcinomas One practical classification of renal cell adeno- tend to have homogeneous contrast enhance- mas and carcinomas is based on their primary ment. Calcifications are more common in chro- morphological features (49): mophil and chromophobe carcinomas than in other types. The latter tend not to invade venous 1. Clear cell type carcinomas structures. 2. Chromophil (papillary) adenomas and carcinomas 3. Chromophobe adenomas and carcinomas Clinical Aspects 4. Duct of Bellini carcinomas General 5. Oncocytic adenomas (oncocytoma) Discussed in the next few sections are the clin- 6. Metanephroid adenomas ical, imaging, and therapeutic aspects of the 7. Transitional cell carcinomas most common type of renal cell carcinoma, 8. Neuroendocrine carcinomas namely clear cell adenocarcinomas. Cystic car- cinomas, chromophil carcinomas, and others Tumors originating from proximal tubules are covered in later sections. (clear cell and chromophilic cell types) make No specific serum markers are available for up approximately 85% of renal cancers (49); renal cell carcinomas. Renal cell carcinomas tumors from connecting tubules and ducts do not produce a-fetoprotein, with an occa- (chromophobic, ducts of Bellini, and oncocytic) sional exception.Although of limited sensitivity make up about 11%. Others are rare. and specificity, a radioimmunoassay of tumor- Collecting duct carcinomas occur in a wide associated trypsin inhibitor appears promising. age range and are more common in males. They Renal cell carcinomas are not common in are centered in the renal medulla but infiltrate children; their prevalence increases with age. extensively, and many patients already have When detected in childhood, these tumors tend 607

KIDNEYS AND URETERS to be at an advanced stage. Yet prognosis dominant transmission with reduced pene- appears favorable even at this stage. trance. A number of these hereditary renal cell Hematuria is still the primary presentation cancers are detected incidentally in asympto- for about 60% of these tumors; a minority matic individuals. Currently a patient present- present with systemic symptoms or a paraneo- ing with bilateral, multiple, or an early onset of plastic syndrome. Flank pain or a palpable mass renal cancer should be investigated for von is found in a minority. Hippel-Lindau disease and possibly other syndromes. Birt-Hogg-Dubé syndrome, proba- bly familiar only to dermatologists, appears to Paraneoplastic Syndrome and be associated with familial renal tumors, includ- Systemic Manifestations ing oncocytomas and papillary renal cell carci- nomas (52). Renal cell carcinoma is associated with several Patients in chronic renal failure undergoing paraneoplastic manifestations. A nephrogenic dialysis who then develop acquired cystic liver dysfunction syndrome without jaundice kidney disease are at increased risk of develop- (Stauffer’s syndrome) or cholestatic jaundice ing renal cell carcinomas. These cancers tend to develops in some patients. be hypovascular and difficult to detect early in Some renal cell carcinomas produce hor- their course. mones that have their own manifestations. Exposure to certain chemicals increases the These include renin (hypertension), parathor- risk of developing renal cell carcinoma. Thus mone (hypercalcemia), erythropoietin (ery- long-term exposure to trichloroethylene, an throcytosis), gonadotropin (gynecomastia), and industrial solvent, leads to an increased inci- adrenocorticotrophic hormone (Cushing’s syn- dence of these tumors. Patients exposed to high drome). Hyperglycemia is rare. Hypercalcemia and cumulative doses of this solvent have muta- occurs in a number of clinical settings, includ- tions in the VHL gene. An association exists ing such malignancies as lung, breast, ovary, between the number of mutations and the squamous cell,and renal,and some hematologic severity of exposure to this solvent (53); the cancers. Hypercalcemia is rare with other geni- mutations are often multiple and show a loss of tourinary malignancies. heterozygosity. Some patients with proven renal cell carci- Radiation therapy–induced renal cell carci- noma and without an obvious cause of serum noma is rare.In the few reported patients,radio- alkaline phosphatase elevation, such as metas- therapy occurred several decades earlier. tases or other liver or bone diseases or preg- With the increased survival seen after therapy nancy, have an elevated phosphatase level, for childhood neuroblastomas, these patients probably due to a paraneoplastic syndrome. In appear to be at increased risk for subsequent some patients alkaline phosphatase normalizes renal cell carcinoma. after nephrectomy, and metastases develop later without phosphatase elevation. Associated Conditions Etiology A synchronous second primary is uncommon, Several syndromes are associated with familial with anecdotal reports describing double renal cell carcinomas, with the best known primary tumors of the kidney and ovary. A being von Hippel-Lindau disease. Renal cell car- higher than expected synchronous association cinomas in this disease tend to be multicentric appears to exist between renal cell carcinoma and bilateral. and non-Hodgkin’s lymphoma. A greater than Hereditary papillary renal cell carcinoma is expected risk of a metachronous second probably in a distinct class of inherited malig- primary also exists in these patients, with the nancies. Germline missense mutations, allelic most frequent second neoplasm being in the losses and duplications of certain chromo- gastrointestinal tract. somes, and mutation of the VHL gene occur Renal cell carcinoma is association with renal in some renal cell carcinomas. Involved cystic diseases, including simple renal cysts, individuals appear to exhibit an autosomal- acquired cystic diseases of the kidney, multilo- 608

ADVANCED IMAGING OF THE ABDOMEN cular cysts, and occasionally even polycystic of these patients. Nevertheless, tumor size is kidney disease. related both to tumor stage and survival, with larger tumors generally being of an increased Incidental Tumor stage and associated with a worse prognosis; keep in mind that some very large renal cell car- Most studies suggest that incidentally discov- cinomas tend to have a favorable prognosis. ered renal cell carcinomas tend to be smaller, Rare spontaneous regression of a renal cell are more often localized to the kidney, show less adenocarcinoma is reported. Most contain vascular invasion, and are of a lower tumor calcifications or a cystic, necrotic cavity and few stage, and these patients have greater survival viable carcinoma cells. compared to a symptomatic tumor. Some studies suggest, however, that no prognostic Screening differences exist for the same tumor stage. Practically, numerous exceptions exist and it is Several sonographic screening studies have difficult to generalize. eventually led to a renal cell carcinoma diagno- Over the last several decades the number of sis in <0.2% of healthy adults. Most detected incidental renal cell carcinomas detected has hyperechoic renal tumors are angiomyolipo- increased considerably, while deaths from renal mas, with others being some other tumor, a cyst, cancer have decreased. A kidney-sparing opera- or simply a normal variant. tion is now much more often feasible than in the past. Of interest is that the examination most Pathologic Study responsible for discovering an incidental tumor is US. Renal adenomas are defined as those having a low nuclear grade tubulopapillary histology, Multicentric Tumors and <5mm in diameter (54); most are located in the cortex and have a discrete border. Autopsy Renal cell adenomas and carcinomas occur studies commonly identify what appear to be bilaterally and are often multicentric (Fig. cortical adenomas. Pathologists use the term 10.10). Multiple synchronous renal cell carcino- renal cortical neoplasm of low malignant poten- mas occur in von Hippel-Lindau disease and the tial for similar low-grade histology but slightly acquired cystic conditions developing in end- larger tumors (54). stage renal disease. The reported prevalence Renal cell carcinomas show considerable his- of multicentricity varies, ranging from 10% to tologic variability. Many adenocarcinomas have almost 50%. Whether a relationship exists varying degrees of tubular differentiation. Some between multicentricity and the size or stage of are difficult to classify. Some require immuno- a primary tumor is not clear, realizing that histochemical staining and electron microscopy whether a partial or total nephrectomy is for adequate evaluation. performed is often based on the size of the One grading scheme consists of applying the carcinoma. worst grade that occupies more than 10% of a A rare patient is found to have multiple renal tumor; the presence of a higher grade, the cell adenomas or adenomatosis. This condition number of satellite tumors, and vein invasion is more common in a setting of end-stage renal are directly proportional to tumor size. Thus disease. small carcinomas tend to contain more grade 1 carcinomas, with their frequency decreasing Growth with increasing tumor diameter as grade 3 cancers increase in frequency; venous involve- Renal cell carcinomas tend to be relatively slow- ment and risk of metastases also correlates growing tumors. Typical tumor volume dou- directly with tumor size. Multifocal carcinomas bling time is over 1 year; on the other hand, are also more prevalent in larger tumors. Necro- metastases grow considerably faster, and the sis, hemorrhage, and cystic degeneration are microenvironment appears to play a role in common in larger cancers. They invade locally, their growth rate. Because of their slow growth, spread to regional lymph nodes, and metasta- watchful waiting appears appropriate for some size mostly hematogenously. 609

KIDNEYS AND URETERS

A

B

Figure 10.10. Bilateral renal cell carcinomas.A: Inferior pole right renal tumor. Arterial phase (B) and delayed phase (C) of smaller left renal midpole tumor (arrow). The patient underwent a right nephrectomy and left wedge resection. (Courtesy of David Waldman, M.D., University of Rochester.) C

Some renal cell carcinomas contain intracel- Detection lular lipid and glycogen; the clear cell appear- ance of chromophobe carcinomas is due in large One problem in comparing results from differ- part to such lipid content. In fact, fat staining for ent studies is that often renal cell carcinomas are intracellular lipid is an established technique to not subclassified into subtypes, yet the subtype identify renal cell carcinomas in urine cytology affects not only its imaging appearance but also specimens. This lipid is rarely detected by CT, the prognosis. For instance, the MR appearance but needs to be taken into account with more of most clear cell carcinomas is different from sensitive MR studies. that of papillary cell carcinomas. And not all of 610

ADVANCED IMAGING OF THE ABDOMEN

these tumors are malignant, thus affecting prog- should be considered malignant. Adenomas nostic considerations. have a similar imaging appearance to that of Although hematuria has numerous causes, carcinomas (Fig. 10.11). Serial follow-up is generally a neoplasm needs to be excluded and problematic because some renal cell carcinomas both upper and lower urinary tracts must be show little or no size change over a year or more. studied. Traditionally, IV urography was the Renal cell cancers tend to be larger, are more initial study for the upper urinary tracts but it round and more encapsulated than metastases. has been supplanted in some institutions by US, Enlarged perirenal lymph nodes, on the other although the documentation for such a change hand, are more common with metastases. is rather weak. In either case, if one study is Ultrasonography is generally the first imag- negative and a bladder tumor has been ing test obtained in children with a palpable excluded, then the other study is indicated. abdominal tumor. Except for a suspected cystic Some investigators believe that with a negative tumor, either contrast CT or MRA is obtained first study, CT should be the second study, but next. here also firm evidence is lacking. With an ambiguous first study, on the other hand, CT Computed Tomography seems reasonable. A minority of renal cell carcinomas contain Computed tomography is considered to be calcifications, with the prevalence increasing accurate in detecting renal tumors. Some with tumor size.Calcifications range from punc- studies have reported CT sensitivities and tate to linear and are located either in the center specificities >98% in detecting these tumors, but or on the periphery. Peripheral calcifications are enthusiasm for these high percentages should seen more often in association with cysts but do be tempered by an inherent build-in patient occur in cystic adenocarcinomas. Calcifications selection bias. Detection varies with tumor size, are less common in most other solid renal with a majority of tumors <5mm not detected. tumors, and detection of calcifications makes a Because most renal cell carcinomas originate renal cell carcinoma more likely. from the cortex, a renal contour bulge is Renal function tends to be preserved except common. On precontrast CT most small tumors with very extensive tumors. Lack of function are isodense to renal parenchyma. Larger should suggest renal vein thrombosis. tumors tend to necrose and bleed and are Using current imaging techniques, in general, heterogeneous in appearance. Postcontrast, any solid non–fat-containing renal tumor carcinomas exhibit variable CT enhancement,

A B

Figure 10.11. A renal adenoma (arrows) is isointense on T1- (A) and T2- (B) weighted MR images. (Source: Burgener FA, Meyers SP, Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.) 611

KIDNEYS AND URETERS

A B

Figure 10.12. Clear cell renal cell carcinoma. A: Corticomedullary phase CT shows a heterogeneously enhancing tumor (arrow.) B: Nephrographic phase CT better defines tumor. (Source: Szolar DH, Kammerhuber F,Altziebler S, et al. Multiphasic helical CT of the kidney: increased conspicuity for detection and characterization of small (<3cm) renal masses. Radiology 1997;202:211–217, with permission from the Radiological Society of North America.)

generally less than normal renal parenchyma hypervascular tumor having inhomogeneous (Figs. 10.12 and 10.13). Small tumors tend to contrast enhancement. have homogeneous contrast enhancement, Computed tomography often detects collat- while larger ones are heterogeneous. A nonen- eral renal capsular veins, and at times even hancing central scar surrounded by an irregular gonadal vein collaterals. These collateral veins enhancing rim is found in some. Larger tumors are a manifestation of the extensive high-flow tend to have an indistinct margin between the state and arteriovenous shunting present in tumor and the adjacent normal parenchyma. many of these highly vascular tumors; they tend A not uncommon appearance for a renal carci- to be more prominent with larger tumors. An noma at initial presentation is that of a large arteriovenous fistula is detected in some cancers. A common assumption is that radiographi- cally visible fat does not occur in a renal cell car- cinoma, and the presence of fat, if detected by CT, essentially excludes a carcinoma. Yet excep- tions do occur. Some renal cell carcinomas encase adjacent fat. Metaplasia within a necrotic tumor results in fat. The presence of fat is even more relevant with MR studies (discussed later).

Ultrasonography Renal cell carcinomas range from hypoechoic to hyperechoic compared to normal renal parenchyma. Acoustic shadowing is not found. Smaller tumors tend toward a hyperechoic appearance, and US cannot differentiate small Figure 10.13. Right renal cell carcinoma. Computed tomo- renal cell carcinomas from angiomyolipomas. graphy identifies a poorly enhancing tumor (arrow). (Courtesy An anechoic or hypoechoic rim is detected in of Algidas Basevicius, M.D., Kaunas Medical University, Kaunas, a minority of solid renal cell carcinomas, a Lithuania.) finding not seen with angiomyolipomas. Con- 612

ADVANCED IMAGING OF THE ABDOMEN

trast enhanced second harmonic US detected a variation exists, however, and some small rim of perilesional enhancement, mostly in the tumors are missed on noncontrast images (Figs. tardive phase, in 86% of renal cell carcinomas 10.14 and 10.15). Larger tumors tend toward a but not in noncarcinomas (55). heterogeneous appearance. The use of gadolin- Doppler US detection of blood flow within a ium improves tumor detection and characteri- cyst suggests a malignancy. Hypervascularity, zation. Postcontrast, carcinomas <3cm in intratumoral high flow arterial signals, and a diameter range from hypervascular (enhance- high pulsatility index within a complex cyst ment greater than that of renal cortex) to hypo- also suggest a malignancy. Some inflammatory vascular (56), while those >3cm tend more tumors, however, have similar findings; also, toward hypovascularity. hypovascular malignancies will be missed. Some renal cell carcinomas contain sufficient In particular, small tumors are difficult to fat that they undergo a loss of signal intensity characterize. on chemical shift opposed-phase MRI (Figs. 10.16 and Fig. 10.17); generally insufficient fat Magnetic Resonance is present to be detected by CT. Magnetic reso- nance findings in these tumors overlap those Magnetic resonance is useful in renal cancer seen with little or no fat-containing angiomy- detection and preoperative evaluation when olipomas, and thus the dictum that renal cell other imaging modalities are limited by arti- adenocarcinomas rarely contain fat should be facts or the use of iodinated contrast agents is modified when applied to MR. These intracellu- contraindicated. Current MRI techniques lar lipid-containing carcinomas are mostly achieve accuracies in renal tumor detection and chromophobe (clear cell) carcinomas, and thus characterization similar to those of CT. chemical shift imaging tends to differentiate Small renal cell carcinomas tend to be hypo- them from other renal cell carcinomas. to isointense on T1-weighted MR images and Chemical shift gradient-echo MRI reveals a iso- to hyperintense on T2-weighted images; significantly higher signal loss in clear cell car- regions of high signal intensity on precontrast cinomas compared to non–clear cell carcinomas T1-weighted images represent intratumoral (57); a significant correlation exists between hemorrhage, while hypointensity on T2- specimen fat staining and signal loss. Signal weighted image is caused by hemosiderin, intensity loss on opposed phase images is not hemorrhage, or necrosis. Considerable intensity seen with all clear cell carcinomas and even in

A B

Figure 10.14. Small alveolar renal cell carcinoma in posterior aspect of right kidney (arrows).The tumor is isointense on T1-weighted (A) and hyperintense on T2-weighted (B) MRI. (Source: Shinmoto H, Yuasa Y, Tanimoto A, et al. Small renal cell carcinoma: MRI with pathologic correlation. J Magn Reson Imaging 1998;8:690–694, with permission of Wiley-Liss, a subsidiary of John Wiley & Sons.) 613

KIDNEYS AND URETERS

A B

Figure 10.15. Small papillary renal cell carcinoma (arrows).The tumor is somewhat isointense on T1-weighted (A) and hypointense on T2-weighted (B) MRI. (Source: Shinmoto H,Yuasa Y,Tanimoto A, et al. Small renal cell carcinoma: MRI with pathologic correlation. J Magn Reson Imaging 1998;8:690–694, with permission of Wiley-Liss, a subsidiary of John Wiley & Sons.)

A B

C D

Figure 10.16. Magnetic resonance fat detection in clear cell renal cell carcinoma. T2-weighted fast spin echo (FSE) (A) and T1- weighted spin echo images (B) identify this tumor (arrow). In-phase (C) and out-of-phase (D) chemical shift gradient echo images show that it has a lower signal intensity on out-of-phase imaging. Chemical shift imaging helps identify fat within clear cell carci- nomas,which differentiates these tumors from other carcinomas (Source:Yoshimitsu K,Honda H,Kuroiwa T,et al.Magnetic resonance detection of cytoplasmic fat in clear cell renal cell carcinoma utilizing chemical shift gradient-echo imaging. J Magn Reson Imaging 1999;9:579–585, with permission of Wiley-Liss, a subsidiary of John Wiley & Sons.) 614

ADVANCED IMAGING OF THE ABDOMEN

A

B

Figure 10.17. Left renal cell carcinoma. Pre- (A) and postcontrast (B) T1-weighted coronal MR images using fat suppression reveal a heterogeneous renal tumor (arrow). (Courtesy of Patrick Fultz, M.D., University of Rochester.)

any one tumor is not uniform, resulting in a het- Staging erogeneous appearance. Also regions of tumor necrosis do not lead to a signal loss. General Stage is the most important prognostic factor in Scintigraphy renal cell carcinoma patients. Two classification systems are in use for staging renal cell carci- Bone scintigraphy can be positive in a hyper- nomas: Robson staging system, more popular in vascular clear cell renal neoplasm. the United States and somewhat simpler to use; An FDG-PET scan detects most but not all and the tumor, node, metastasis (TNM) system renal cell carcinomas. Angiomyolipomas and (Table 10.6). Both suffer limitations to staging some other tumors result in false-positive accuracy and both tend to understage more findings, and in renal cancer detection PET often than overstage. offers no significant advantage over other Lymphatic spread of renal cell carcinoma imaging modalities. Positron emission tomog- during initial detection is about 10% or less; raphy depicts solid renal neoplasms as regions most affected patients have advanced stage of increased uptake and cysts are seen as disease, distant metastases, a large tumor, and photopenic regions. poor survival.

Biopsy Imaging In most instances a renal cell carcinoma is diag- nosed with imaging, and a biopsy or aspiration Either a chest radiograph or chest CT is helpful cytology is not obtained prior to surgery. Even in a search for metastases, although which of tumors with an atypical imaging appearance are these two is preferred is debatable. generally investigated surgically. In particular Currently helical CT is the primary staging for small, discrete lesions, the efficacy of aspira- modality used. How reliable is CT in staging tion cytology in determining tumor pathology renal cell carcinoma? A number of studies is limited and has led to complications. suggest that overall T-staging accuracy is only Currently the primary role for aspiration about 60% (58). Although of prognostic impor- cytology is in a nonoperable patient where a tance, the low CT sensitivity and specificity in tissue diagnosis needs to be established prior to detecting fat invasion is not crucial because per- alternative therapy or if metastases or lym- inephric fat is also resected during a nephrec- phoma are suspected. tomy for cancer and imaging detection of 615

KIDNEYS AND URETERS

Table 10.6. Tumor, node, metastasis (TNM) classification of enhanced and time-of-flight sequences primary renal cell carcinoma achieved good T and M staging, but was poor Primary tumor: for N staging (59); MRI can readily assess Tx Primary tumor cannot be assessed venous invasion. T0 No evidence of primary tumor Both CT and MR detect adenopathy but T1a Tumor 4cm or less in greatest dimension cannot determine whether an enlarged node is limited to kidney secondary to inflammation or tumor. Some T1b Tumor more than 4cm but less than 7cm in authors believe that CT staging accuracy for greatest dimension limited to kidney lymphadenopathy is close to chance (58). The T2 Tumor more than 7cm in greatest dimension limited to kidney. role of MR in evaluating adenopathy and metas- T3a Tumor invades adrenal gland or perinephric tases continues to expand. Ultrasonography tissues but not beyond Gerota’s fascia appears inferior in adenopathy detection. T3b Tumor invades renal vein or vena cava below A reasonable preoperative staging strategy in diaphragm the occasional pregnant woman developing a T3c Tumor grossly extends into vena cava above malignant renal tumor consists of abdominal diaphragm or invades wall of vena cava US and MRI to define local tumor extension T4 Tumor invades beyond Gerota’s fascia. and a chest radiograph to detect pulmonary Lymph nodes: metastases. Nx Regional lymph nodes cannot be assessed. Either CT or MR is used to detect adjacent N0 No regional lymph node metastasis. organ invasion. Bone scintigraphy has a limited N1 Metastasis in a single lymph node role in initial tumor staging unless clinical or N2 Metastasis in more than one regional node laboratory evidence suggests bone involvement. Distant metastasis: Mx Distant metastasis cannot be assessed M0 No distant metastasis Vascular Invasion M1 Distant metastasis Even small carcinomas tend to invade adjacent Tumor stages: renal vein branches, but extension as a tumor Stage I T1 N0 M0 thrombus into the renal vein and inferior vena Stage II T2 N0 M0 cava is uncommon for small tumors; the risk of Stage III T1 N1 M0 invasion increases with tumor size, and venous T2 N1 M0 extension to the right atrium is not uncommon T3 N0 M0 with large tumors (Figs. 10.18 and 10.19). Obvi- T3 N1 M0 ously, detecting venous extension is important Stage IV T4 N0 M0 in planning resection. Imaging should also T4 N1 M0 any T N2 M0 detect any anomalous vascularity. Angiography any T any N M1 currently does not have a role in the staging of renal cell carcinomas but is occasionally per- Note: Above classification applies to clear cell renal carcinoma,pap- formed to define blood supply and as a prelude illary renal carcinoma, chromophobe renal carcinoma, and collect- to preoperative embolization (Fig. 10.20). ing duct renal carcinoma. Contrast CT and MRA have supplanted angiog- Source: From the AJCC Cancer Staging Manual, 6th edition (2002), published by Springer-Verlag,New York,NY,used with permission of raphy’s role both in a search for renal vein inva- the American Joint Committee on Cancer (AJCC), Chicago, IL. sion and in providing a vascular road map for the surgeon (Fig. 10.21). Even small vessel invasion affects prognosis. perinephric fat invasion does not influence One of the reasons is that a tumor thrombus surgery. contains more dividing cells than a primary Dynamic MRA is an alternate in place of CT tumor, that is, a tumor thrombus has a shorter in a setting of severe renal dysfunction, exten- tumor doubling time and thus is more aggres- sive polycystic kidney disease, or a contraindi- sive, a conclusion reached by comparing the cation to iodinated contrast media. Potentially, proliferation index of primary renal cell carci- MR could replace CT in staging these tumors. nomas and their corresponding neoplastic Compared to surgical and pathologic staging, thrombi (60). Patients with renal cell carcino- MRI using T1-, T2-weighted, gadolinium mas exhibiting micro- or macrovascular 616

ADVANCED IMAGING OF THE ABDOMEN

A

B

Figure 10.18. Venous extension of renal cell carcinoma. A: A cancer has invaded the renal vein to the level of inferior vena cava (arrow). B: With further growth, the cancer now extends above one of the hepatic veins (arrow).

A B

Figure 10.19. Venous invasion of renal cell carcinoma. A,B: Two precontrast CT images identify a right renal tumor and a hypo- dense right renal vein (arrow) and vena cava. C: A contrast- enhanced image identifies tumor vessels within the inferior vena cava (arrow).(Courtesy of Algidas Basevicius,M.D.,Kaunas Medical C University, Kaunas, Lithuania.) 617

KIDNEYS AND URETERS

Figure 10.20. Right renal cell carcinoma. Contrast filling and stretching of intrarenal vessels in a vascular tumor are evident. Metastases were also detected. (Courtesy of David Waldman, M.D., University of Rochester.) Figure 10.22. Coronal MR image identifies an intraluminal infe- rior vena cava filling defect defect (arrow) in a patient with a left renal cell carcinoma. (Courtesy of Brian R. Herts, M.D., Cleveland Clinic Foundation.) invasion have a significantly worse prognosis than those without such invasion; prognosis also varies with the extent of vascular invasion. Detection of small vessel invasion is beyond the Imaging can determine whether the inferior resolution of the current imaging modalities. vena cava is simply compressed by an extrinsic tumor or whether a tumor extends intralumi- nally (Fig. 10.22). The extent of inferior vena caval involvement determines the type and complexity of the resection. To reduce blood loss, surgery in a setting of inferior vena cava invasion necessitates either direct caval clamp- ing or the use of cardiopulmonary bypass. Imaging should thus identify whether a throm- bus barely involves the vena cava,remains below most inferior hepatic veins, terminates between the hepatic veins and the diaphragm, or extends above the diaphragm and possibly into the right atrium. Contrast-enhanced imaging differenti- ates between a bland thrombus and a tumor thrombus. Invasion of the caval wall, although not common, is difficult to determine with imaging, which is unfortunate because invasion necessitates partial vena caval resection. MR is superior to both CT and US in detecting inferior vena cava tumor thrombi, although technically good CT is often adequate. CT tends not to iden- Figure 10.21. Transverse MR image reveals a left renal cell car- tify the cephalad extent of a tumor thrombus. cinoma with renal vein invasion (arrow). (Courtesy of Brian R. Preoperative helical CT detects renal vein Herts, M.D., Cleveland Clinic Foundation.) invasion with a sensitivity of >80% and a 618

ADVANCED IMAGING OF THE ABDOMEN specificity approaching 100%; reported sensi- Interleukin-2 was approved by the Food and tivity varies depending on whether small Drug Administration in 1992 for treatment of intrarenal venous thrombi are considered or metastatic renal cell carcinoma. The response to not. False-positive results occur due to interleukin-2 therapy is difficult to evaluate with unopacified blood producing a flow void arti- imaging due to residual deformity. 2-[18F]- facts. Magnetic resonance imaging should fluoro-deoxy-D-glucose—PET imaging appears detect all distal renal vein involvement; cavog- useful in these patients, but if interleukin-2 raphy should be considered if neither CT nor therapy is contemplated, a pretherapy scan aids MR is satisfactory. in establishing a baseline. Ultrasonography identifies tumor venous Interferons, produced by the body in extension as renal vein or inferior vena cava dis- response to viral infections, also have an anti- tention by echogenic material and decreased or tumor effect due to direct cytotoxicity and absent flow in this segment, as detected by activation of a number of immunologic path- Doppler US. Tumors limited to the intrarenal ways. Both recombinant a-interferon and g- veins account for some false-positive results. interferon, at times combined, have been used The current role of color Doppler US in detect- to treat metastatic renal cell carcinoma, ing tumor venous extension appears to be in although little data is available on the effect of those patients with an incomplete or equivocal interferon therapy on survival in patients with CT examination and unavailability of MR. inoperable renal cell carcinoma. Preliminary With a suspected carcinoma invading the results suggest prolonged survival in interferon- inferior vena cava and possibly extending treated patients. into the right atrium, transesophageal echocar- Cimetidine blocks histamine-mediated diography is useful to establish the cephalad activation of suppressor T-cells and appears to extent of a cavoatrial tumor and aid surgical have antitumor immune properties. Anecdotal management. reports suggest a response in some patients If needed, intraoperative US defines the treated with cimetidine for metastatic renal cell extent of vena caval invasion. Ultrasonography carcinoma. may aid instrument placement and decrease the risk of tumor thrombus dislodgment. Resection Therapy Refinements in surgical technique have led to more conservative surgery such as enucleation Controversy surrounds the therapy of small and heminephrectomy. Current experience sug- (<2cm) renal cell tumors of low malignant gests that in selected patients conservative potential. In most patients these tumors are surgery is as effective as radical surgery.With an resected (often with a nephron-sparing resec- increasing number of small tumors detected tion), but in a high surgical risk patient an incidentally, conservative (nephron sparing) argument can be made for CT follow-up and surgery achieves good long-term results. Com- resection only if tumor growth ensues. Conven- plicating the issue, however, is multicentricity of tional chemotherapy and radiotherapy are some small tumors. Also, an invasive growth largely ineffective for renal cell carcinomas. pattern, high-grade nuclear atypia, and Bellini duct carcinomas are associated with a poor Medical Therapy prognosis.Some surgeons believe that even with a localized renal cell carcinoma radical nephrec- Interleukin-2 is a T-cell growth factor that also tomy has a role; it has low morbidity, excellent enhances natural killer cell function. Its prelim- local tumor control, and high survival. These inary use suggests a role in metastatic renal cell surgeons maintain that for patients with a carcinoma. The response appears to be greater normally functioning contralateral kidney, for metastatic foci rather than for the primary no convincing evidence exists to justify a renal tumor, with an objective response rate of nephron-sparing operation on a routine basis. about 15% to 30% of patients. Tumor regression Nevertheless, laparoscopic wedge resection of is achieved in up to one third of patients, with smaller renal carcinomas is successfully per- a complete response in an occasional one. formed. One indication for nephron-sparing 619

KIDNEYS AND URETERS

surgery is bilateral renal cell carcinomas. tumors have round contours and enhance with Because of its high spatial resolution, intraoper- contrast, resolving eventually except for a small ative US is very useful in such a setting to better cortical scar. define indeterminate lesions, revealing more An occasional solitary metastasis is resected. extensive or satellite lesions and establishing Pulmonary resection for metastatic renal cell tumor margins. Intraoperative US and frozen carcinoma is viable therapy for some selected section biopsy may spare the patient a slow-growing tumors. nephrectomy. Successful tumor enucleation implies that a Tumor Embolization tumor has a discrete border (i.e., has a pseudo- capsule). Such a pseudocapsule is best defined Need for a definitive diagnosis prior to tumor by T2-weighted MRI and dynamic T1-weighted embolization or ablation therapy is obvious, yet MRI. a number of benign tumors have undergone Lymphadenectomy is indicated for patients needless therapy before a diagnosis is estab- with enlarged lymph nodes or a large tumor but lished. This problem appears more acute in the without distant metastases and,in general,those kidney than the liver and often revolves around tumors believed to be curable. On the other nonfat-containing angiomyolipomas. hand, the vast majority of patients with lymph Tumor embolization is performed both as a node involvement already have additional, stand-alone procedure and preoperatively. mostly multifocal metastases, and thus exten- Embolization of extensive renal cell carcinomas sive lymph node dissection on a routine basis as decreases blood loss and simplifies surgery part of a radical nephrectomy appears to have a (Figs. 10.23 and 10.24). Some patients develop limited effect on survival (node dissection is spontaneous renal vein-to–portal vein ana- useful, however, for staging). stomoses, and such anastomoses need be Similar to other malignancies, a postopera- considered prior to embolization. Aside from tive imaging study is useful in establishing a embolization, selective angiography aids in baseline for detecting future tumor recurrence. planning a nephron-sparing operation. Invariably, the underlying anatomy is distorted Embolization in a setting of tumor thrombus at surgery. At times imaging after a nephron- in the renal vein or inferior vena cava carries a sparing operation reveals a pseudotumor; these potential risk of distal tumor embolization. A

A B

Figure 10.23. Hypervascular renal cell carcinoma. A: Arteriography reveals a right renal tumor (arrows). B: Successful embolization of the major artery feeding this tumor was performed. (Courtesy of David Waldman, M.D., University of Rochester.) 620

ADVANCED IMAGING OF THE ABDOMEN

A B

Figure 10.24. Embolization of right renal cell carcinoma. Images before (A) and after (B) renal artery spring coil embolization prior to surgery.A considerable decrease in tumor vascularity is evident,but some feeding vessels still remain.(Courtesy of David Waldman, M.D., University of Rochester.)

suprarenal inferior vena cava filter minimizes replaced by a hypointense zone, identified on this risk. T2-weighted images acquired intermittently A major role for tumor embolization is palli- during ablation. Preliminary results are encour- ation of hemorrhage or pain in inoperable aging (63). One reported complication is skin patients. Superselective embolization of inoper- metastasis at the electrode insertion site. Iso- able renal tumors is occasionally performed in lated local recurrences after radical nephrec- patients with a solitary kidney; insufficient data tomy are also amenable to radiofrequency preclude drawing any firm conclusions about ablation (64). Contrast enhanced CT immedi- the validity of such an approach. ately after ablation detects residual viable tumor. US identifies a hyperechoic interface at Other Ablation Therapy the junction of normal renal parenchyma and frozen tissue. Laparoscopic cryoablation of small renal tumors is feasible (61); the efficacy of such Therapy for Bilateral Tumors therapy is incompletely studied. Percutaneous injection or coagulation Conservative surgery, such as heminephrec- therapy of renal neoplasms has lagged similar tomies, is the initial consideration for bilateral counterparts in the liver. More than in most and synchronous renal cell carcinomas. Occa- other organs, renal neoplasm therapy has sionally bilateral nephrectomy and chronic dial- remained in the province of the urologist and ysis is the only viable option, in which case renal generally intraoperative US guidance is used. transplantation should be considered. Feasibility of percutaneous image guided radiofrequency ablation of renal cell carcino- Recurrence/Follow-Up mas has been established in poor surgical risk patients (62). Interactive MR image guided Renal carcinoma metastases more often are of a radiofrequency interstitial thermal ablation of higher grade of malignancy than the primary renal cell carcinomas is a new field. A low field rather than of a lower grade. Thus prognosis in strength unit monitors until the tumor is patients with metastatic disease is based both 621

KIDNEYS AND URETERS on primary tumor grade and on that of the with stage T3 disease undergo abdominal CT metastases. every 6 months for the first 2 years (65). A small tumor detected on a postcancer A nephrectomy in the presence of metastases resection imaging study is generally considered is often justified as an attempt to prolong life or to be a recurrence or a new cancer (assuming it improve quality of life. A cure even after resec- was not evident on preresection imaging). tion of a solitary metastasis is not common. The presence of small synchronous renal cell carcinomas and an increased prevalence of metachronous cancers suggest that serial Sites of Metastases imaging surveillance, possibly on an annual Renal cell carcinoma is unpredictable in its basis, of residual ipsilateral renal tissue (if any) spread, and metastases develop to unusual and the contralateral kidney is indicated. sites. Most common are metastases to the lungs Initially most lung metastases are asympto- and bone. Metastasis to the pancreas is not matic and are detected by screening. Bone rare, in spite of statements to the contrary by metastases, on the other hand, become sympto- some authors. Some metastases are already matic early on. Chest follow-up is with either evident at the time of initial cancer diagnosis; in chest radiograph or CT, with proponents advo- fact an occasional metastasis is detected and cating either one or the other. Certainly CT is resected even before the primary tumor site is more sensitive in detecting metastases both in discovered. the chest and adjacent bones (assuming bone Spread to the adrenal glands is by either windows are used) and more often detects direct extension or metastasis. Direct adrenal the rare solitary and resectable lung metastasis. invasion is uncommon by a superior pole tumor On the other hand, CT also detects benign less than several centimeters in diameter. Some incidental nodules, often leading to unnecessary of these metastases are from a contralateral biopsy. kidney, presumably hematogenous in nature. Currently CT is the study of choice to detect Unlike transitional cell carcinomas, metasta- abdominal recurrence. Ultrasonography is less sis along the ipsilateral ureteral stump following sensitive than CT. Magnetic resonance imaging a previous radical nephrectomy is rare for renal is rarely employed for primary screening, cell carcinomas. although preliminary evidence suggests that it Resection of liver metastasis is often feasible, is equal, if not superior, to CT in tumor detec- especially with a single focus, with prolongation tion. It has a role in select patients, such as those of survival but at a cost of a high mortality rate. with an iodine allergy. Nuclear scintigraphy requires separate scanning for bone, liver- spleen, etc. Nuclear scintigraphy is currently the Late Recurrence examination of choice in detecting bone metas- tases, but whether serial scans are beneficial in Late recurrence is arbitrarily defined as 10 years the absence of bone symptoms is debatable, and or longer postnephrectomy. Tumor recurrence they are not often employed. years after initial therapy suggests that use of a Rarely, a metastasis regresses spontaneously. 5-year survival time frame is too short for this Thus spontaneous regression of pulmonary tumor. Renal cell carcinoma can recur years metastases does occur. One should realize, after nephrectomy.Anecdotal reports abound of however, that not all lung tumors in a patient pulmonary, pancreatic, and other metastases with known renal cell carcinoma are metastases. developing many years after nephrectomy. In general, prognosis is better in those with late rather than early recurrence. Prognosis Based on tumor recurrence patterns, one rec- Cystic Carcinomas ommended follow-up schedule is based on tumor stage: patients with stage T1 carcinoma About 10% of all renal cell carcinomas are are evaluated yearly clinically, those with stage cystic. Complicating the picture is that more T2 disease also have an annual chest radiograph often a solid renal cell carcinoma is associated and abdominal CT every 2 years, while those with an incidental cyst close by, such as a simple 622

ADVANCED IMAGING OF THE ABDOMEN cyst or acquired cystic disease of the kidney.The a simple renal cyst was resected; 1 year later solid component of most cystic carcinomas is numerous cysts encased the kidney, with cyst located close to underlying renal parenchyma. walls lined by a single layer of cuboidal epithe- Rarely, a carcinoma arises from the outer lium (67). The degree of differentiation argued surface of what appears to be a simple cyst. against a carcinoma and suggested a cystic Cystic carcinomas are classified into several mesothelioma, cystic lymphangioma, or even a patterns: multilocular, unilocular, necrotic, and multicystic dysplastic kidney, yet the tumor those originating in the wall of a simple cyst; recurred repeatedly, invaded bowel, and became histopathologically, multilocular carcinomas almost solid. can be divided into macrocystic and microcys- Aspiration cytology tends to be negative with tic. Macrocystic tumors appear multilocular on cystic neoplasms, and a negative aspirate is of US and contrast-enhanced CT; angiography limited significance. A number of cystic carci- reveals neovascularity in most tumors. When nomas yield clear fluid, but this finding cannot first detected, most multilocular cystic renal cell be relied on. Comparing fluid aspirated from carcinomas already have a significant cystic benign renal cysts and cysts containing a carci- component. When small, however, imaging noma, interleukin-6, basic fibroblast growth shows them to be solid, although histology of factor concentrations, and epidermal growth resected specimens does reveal a microcystic factor levels tend to be higher in malignant component. On precontrast CT, microcystic cysts. tumors range from hypodense to hyperdense Laparoscopic biopsy, followed by open resec- depending on the amount of hemorrhage. They tion is an option for complex cysts suspicious exhibit slight CT contrast enhancement, are for cancer. hyperechoic, and do not appear cystic on US; Prognosis is similar both for solid and cystic MRI reveals high signal intensities on both carcinomas. T1- and T2-weighted images, and dynamic enhancement shows an irregular contrast enhancement pattern. Angiography of these Chromophil (Papillary) Adenoma small tumors typically shows little evidence of and Carcinoma neovascularity. Unilocular carcinomas consist of a cystic Renal papillary adenomas are common renal tumor containing either an irregular wall or epithelial neoplasms; most are in the several mural nodules, detected by contrast-enhanced millimeter size range. Papillary renal cell carci- CT and US. Necrotic tumors range from ane- noma is the second most common carcinoma of choic to varying echogenicity, while their CT the renal tubules. These neoplasms manifest an appearance varied from cystic with mural adenoma-to-carcinoma evolution, and a contin- nodules to an irregular tumor. Neovascularity is uous tumor spectrum ranging from papillary common in viable tumor surrounding necrotic adenoma to papillary carcinoma is encoun- regions. tered. Synchronous papillary renal adenomas US using Levovist enhanced pulse inversion and carcinomas occur. Several families of a harmonic imaging shows that the thick wall of hereditary papillary renal cancer syndrome are both cystic renal cell carcinomas and complex reported. inflammatory cysts has intense contrast enhan- These tumors tend to be multifocal and bilat- cement during the arterial phase (66). eral. They have specific immunohistochemical Larger cystic renal cell carcinomas tend to and genetic features distinct from other renal have a complex cystic imaging appearance. In carcinomas. general, a cyst with a thick or irregular wall, Detected papillary renal cell carcinomas tend prominent septa, wall calcifications, septations, to be large, well-defined, and relatively hypo- or associated with an adjacent soft tissue vascular, and tend to enhance less with CT con- component suggests a malignancy. Neverthe- trast than do clear cell tumors. Some exhibit less, overlap occurs between benign complex occasional short intratumoral contrast-related cysts and cystic malignancies, and tumor stranding. Computed tomography revealed identification is difficult. Temporal changes nine of 10 papillary renal cell carcinomas to be occur in some of these tumors. As an example, rounded, well-circumscribed, and sharply mar- 623

KIDNEYS AND URETERS ginated tumors containing central hypodense relationship of this tumor with transitional cell regions representing necrosis, surrounded by carcinomas. viable tumor seen as contrast-enhancing ser- This rare, aggressive neoplasm manifests in a piginous tissue (68).An occasional cystic tumor younger population than the more common contains multiple nodules. Some are associated clear cell carcinoma. It develops in children. with cholesterol necrosis and these tumors Hematuria is a common presentation. Some mimic an angiomyolipoma (69). patients have positive urine cytology. It is not Although US detects fewer papillary tumors uncommon to find metastases at the time of first than CT, it aids in evaluating any cystic presentation. component. Because duct of Bellini carcinomas originate Papillary renal tumors tend to be hypointense predominantly centrally in the medulla, they on T2-weighted images, often due to hemo- tend not to deform the renal outline, a finding siderin, hemorrhage, and necrosis, although distinguishing these tumors from more hypointensity in some appears to be intrinsic to common renal cell carcinomas. Imaging shows the papillary component. a solid, hypodense, and hypovascular or even These tumors often pose a diagnostic avascular renal tumor with limited contrast dilemma because of their benign appearance. enhancement. They tend to protrude into the central sinuses. Chromophobe Carcinoma A chromophobe renal carcinoma is considered Oncocytoma a subtype of renal cell carcinoma exhibiting Clinical a low chromosome number. Histology reveals a mix of clear cells containing lipid and glycogen Some authors classify oncocytomas as a type of and eosinophilic cells. renal adenoma. Epithelial oncocytes have a These carcinomas occur in childhood. Prog- granular eosinophilic cytoplasm rich in mito- nosis is considerably better than with conven- chondria. These cells are not limited to onco- tional renal cell carcinomas. cytomas but are also found in granular cell These tumors range from hypovascular to carcinomas (oncocytic adenocarcinomas) and avascular. A minority of chromophobe carcino- some clear cell adenocarcinomas. Oncocytomas mas contain a central scar. occur in several organs, but most often are found in kidneys. Mitochondrial DNA analysis Duct of Bellini Carcinoma suggests that a specific mitochondrial DNA alteration is responsible for oncocytomas. Carcinoma of ducts of Bellini, or collecting duct Renal oncocytomas are more common in carcinoma, originates from ducts of Bellini some families. These tumors are often detected epithelium in the distal tubules located in the incidentally in asymptomatic individuals; some renal medulla. The prevalence is about 1% of all are multiple and bilateral, with a rare patient renal carcinomas. having hundreds of nodules scattered through- Whether this tumor should be classified as a out both kidneys. separate carcinoma or is a variant of a renal cell Renal oncocytomas are probably benign carcinoma is not clear.Histologic differentiation tumors consisting primarily of oncocytic cells. from a more common renal cell carcinoma is They appear to originate from the cortical part difficult, although morphologically, immuno- of collecting tubules. Their prevalence is chemically, and cytogenetically it can be defined difficult to gauge because some have been mis- as a separate entity. Chromosome analysis sug- classified as renal cell carcinomas or chromo- gests that molecular development of this neo- phobe carcinomas. Especially in the older plasm is different from that of a more common literature an occasional one has been reported renal cell carcinoma. Specific tumor-suppressor to metastasize, but whether these are mis- genes appear to be involved in its pathogenesis. classified is difficult to gauge. Embryologically,collecting ducts originate from Percutaneous biopsy or cytology tends to be the wolffian duct system, similar to renal calyces misleading because some oncocytomas mimic and ureters, and a point can thus be made of a a granular renal cell carcinoma. On the other 624

ADVANCED IMAGING OF THE ABDOMEN hand, a biopsy or aspiration cytology from a precede, are synchronous with, or are metachro- region rich in oncocytes may not detect an adja- nous with a malignant urothelial tumor, and cent focus of carcinoma unless extensive sam- thus the discovery of one requires a search for pling is performed. Pathologically, a diagnosis other urinary tract tumors. of an oncocytoma is one of exclusion by elimi- The imaging appearance of papillomas is nating other, more ominous, tumors. similar to that of other urothelial neoplasms. An occasional renal oncocytoma ruptures. They range from sessile to pedunculated. The Adjacent fat next to such a ruptured oncocy- differential diagnosis includes transitional cell toma can mimic an angiomyolipoma. carcinoma, blood clots, a fungus ball, calculi, fibroepithelial polyp, and malacoplakia. Imaging Local excision appears sufficient for these tumors. Oncocytomas are solid, homogeneous, well- marginated, and often large tumors. They have no specific imaging findings; CT, US, and MR Transitional Cell Carcinoma simply reveal a solid, well-marginated tumor. Clinical Especially when small, their imaging appear- ance is indistinguishable from that of renal cell Urothelial origin malignant neoplasms include carcinomas. In distinction to renal adeno- transitional cell carcinoma, squamous cell car- carcinomas, necrosis and hemorrhage are not cinoma, and adenocarcinoma. Of these, transi- common, although larger oncocytomas tend to tional cell carcinomas predominate and, after contain a central stellate scar that mimics the renal cell adenocarcinomas, represent the necrosis seen in a renal cell carcinoma. Cystic second most common renal neoplasm in adults. changes and calcifications are rare. They tend to A minority contain a squamous cell metaplasia be somewhat hypervascular. In general, imaging component. A rare transitional cell carcinoma can suggest an oncocytoma but will not differ- contains a sarcomatoid component. Data from entiate it from a renal adenocarcinoma. the Dutch hereditary nonpolyposis colorectal Oncocytomas are hypointense on T1- cancer registry suggest that patients with hered- weighted MR images but vary in intensity on itary nonpolyposis colorectal cancer are at an T2-weighted images. About half have a well- increased risk of developing upper urinary tract defined capsule. Post-MR contrast a minority of transitional cell carcinomas (70). oncocytomas reveal a “spoke-wheel” enhance- Among transitional cell carcinomas originat- ment pattern. These MR findings do not exclude ing in renal collecting systems, roughly one a renal cell carcinoma. quarter are in an upper calyx, one quarter in a lower calyx, one quarter in renal pelvis, about 5% in a middle calyx and the rest are more Urothelial Tumors extensive; in the ureters, slightly under 10% are Papilloma in the upper segment, 20% in the middle, slightly under 50% in the lower segment, and Papillomas are transitional cell epithelial 20% in the distal ureteral. A rare patient has the tumors that are difficult to classify. Histolo- entire ureter affected. A number of reports gically, differentiation from a low-grade tran- describe a ureteral stump transitional cell carci- sitional cell carcinoma is difficult, and noma developing years after a nephrectomy for controversy exists about whether they are a benign or malignant condition. indeed a separate benign entity or whether they The most common clinical finding with these represent a spectrum of transitional cell carci- tumors is intermittent hematuria, followed by nomas. They are rare in the upper urinary tract. flank pain. Ureteral obstruction and a nonfunc- A male predominance is evident. tioning kidney develop eventually and thus a The even rarer upper urinary tract inverted need for retrograde pyelography. A rare papillomas are of uncertain malignant poten- obstruction leads to ureteral rupture. tial. Etiology of this proliferative tumor is While positive cytology is obviously diagnos- unknown, and histopathologic diagnosis dif- tic, negative cytology does not exclude a transi- ficult. Of note is that some inverted papillomas tional cell carcinoma. Especially with intrarenal 625

KIDNEYS AND URETERS tumor, washings tend to be nondiagnostic.Also, differentiating a superficial tumor from one positive cytology does not identify the site of invading muscle layers or renal pelvis. Proximal origin. hydronephrosis tends to result in overstaging; CT sensitivity and specificity is considerably Imaging greater in assessing renal parenchymal invasion than in detecting ureteral or perirenal fat inva- Transitional cell carcinomas range from poly- sion. Staging accuracy is improved by decreas- poid, to nodular, to flat. Some polypoid ones are ing CT thicknesses through the tumor. on a stalk; these tend to be low grade and are If sufficiently large, US shows these tumors to often associated with adjacent ureter dilation, be hyperechoic to renal parenchyma. but differentiation from a stone is difficult in Endoluminal US holds promise; tumor loca- some patients, even with retrograde pyelogra- tion, size, and staging can be studied with this phy. The flat type, often containing squamous technique. cell carcinoma components, tends to infiltrate, These tumors are hypointense on T2- has little if any intraluminal component, and weighted MRI. Some of these hypovascular car- usually is of a higher grade malignancy; as cinomas enhance considerably with contrast expected, this type is more difficult to detect. If MRI. extensive, a more proximal infiltrating one will obstruct (“amputate”) a calyx. Calcifications are Therapy/Survival rare. When large, these tumors infiltrate exten- Upper tract carcinoma in situ is occasionally sively and mimic a renal cell carcinoma, treated by bacillus Calmette-Guérin instillation; although, being centrally located, they are less although normalization of urinary cytology is prone to producing a renal contour abnormal- reported, only limited studies are available. ity. Some intrarenal transitional cell carcinomas Ureteroscopic biopsy and cytology are are highly invasive, become necrotic, and helpful in defining and grading these tumors. involve a large portion if not the entire kidney. Tumor stage and grade are interrelated and have Only a rare transitional cell carcinoma extends prognostic significance; most tumors with a low into the vena cava as a tumor thrombus. or moderate grade are at a low stage and those Being urothelial in origin, pyelography (IV, with a high grade are at a stage T2 or T3. retrograde or antegrade) should have a high Among Japanese patients with renal pelvic or tumor detection rate, even higher than with CT ureteral cancer who underwent lymph node dis- and gray-scale US. A major limitation of IV section, no lymph node involvement was found pyelography is the lack of sufficient contrast in about two thirds (71). The 5-year survival rate opacification. was 79% for pN0, decreasing to 12% for pN1, Computed tomography identifies a transi- 20% for pN2, and 0% for pN3. These are some- tional cell carcinoma as a soft tissue density what biased statistics because only patients tumor adjacent to water density urine. It is iso- selected for lymph node dissection are included. dense to renal parenchyma. Its density is lower Because of these tumors synchronous and than that of blood clots. Computed tomography metachronous potential, a nephroureterectomy identifies a cystic component in a minority. is generally performed. A search for associated These tumors enhance slightly after contrast, bladder cancers is also warranted. Close follow- although enhancement is less than that of renal up is necessary for metachronous tumors, espe- parenchyma.At times a lucent stone is in the dif- cially during the first several years after initial ferential diagnosis, but CT should differentiate surgery. even a uric acid stone, which is denser than a transitional cell carcinoma. Nephrogenic Metaplasia/ Computed tomography is used in staging Adenoma/Adenocarcinoma transitional cell carcinomas, although the type of staging criteria used and the presence of Nephrogenic metaplasia, or nephrogenic hydronephrosis influence staging accuracy. adenoma, is a rare, benign urothelial condition While CT detects invasion of adjacent struc- histologically consisting of glandular struc- tures and distant metastases, it is limited in tures. This condition is more common in the 626

ADVANCED IMAGING OF THE ABDOMEN bladder but occasionally is detected in the Sarcomatoid Carcinoma ureters or renal collecting systems. Most meta- plasias are associated with chronic infection, Sarcomatoid carcinomas contain elements of and the pathogenesis presumably includes adenocarcinoma, transitional cell carcinoma, metaplasia in response to a prior inflammation and sarcoma. Some of these carcinomas are or trauma. Some tumor cells show severe related to prior radiation therapy to other nuclear atypia and staining for anti-p53, sug- organs. About 5% of renal cancers are histolog- gesting that p53 has a role in adenoma-to-ade- ically sarcomatoid in nature.Survival of patients nocarcinoma transformation of these tumors.A with these cancers is measured in months. rare adenoma is cystic. Imaging findings of most sarcomatoid carci- Although nephrogenic metaplasia is consid- nomas are similar to the more common renal ered to be a benign condition, a rare primary adenocarcinomas. nephrogenic (urothelial) adenocarcinoma is reported, at times consisting of nephrolithiasis, Medullary Carcinoma nuclear atypia suggesting a malignancy, a tubulovillous adenoma, and intestinal metapla- Renal medullary carcinoma is a rare collecting sia in adjacent epithelium. A typical scenario duct neoplasm affecting teenagers and young consists of urography in a patient with pain and adults with sickle cell trait or hemoglobin SC hematuria revealing a ureteral tumor, a biopsy disease. Presumably an unidentified genetic identifies nephrogenic metaplasia, and this component is a factor in its pathogenesis. The segment is resected. tumor has a distinctive microscopic appearance Although resection should be curative, recur- consisting of a diffuse and glandular growth rence is not uncommon. Whether recurrence is pattern, an inflammatory infiltrate, and the due to incomplete resection or a new focus from presence of rhabdoid/plasmacytoid cells or diseased urothelium is often unknown. even sarcomatoid cells. This entity should be considered in a young patient with sickle cell trait or hemoglobin SC Squamous Cell Carcinoma disease who develops hematuria. Distant metas- Squamous metaplasia (also known as keratiniz- tasis at the initial presentation is not uncom- ing and desquamating malpighian metaplasia) mon. These tumors are centrally located and and subsequent squamous cell carcinoma infiltrate the renal parenchyma and renal sinus; develop in a setting of chronic urolithiasis or occasionally a necrotic tumor communicates infection. Upper tract infection with Schisto- with the collecting system. They show heteroge- soma hematobium is associated with this tumor. neous contrast enhancement, presumably due No distinguishing imaging characteristics to necrosis. Venous invasion and nodal metas- identify squamous cell metaplasia. At best, it tases are common. appears as a polyp, often in the renal pelvis. It is This is an aggressive malignant neoplasm diagnosed either from a biopsy specimen or on having a poor prognosis. The interval from histologic study after nephroureterectomy. diagnosis to death averages only several These carcinomas range from flat, ulcerated months; no objective response is seen to chemo- plaques to large, bulky renal pelvis tumors. and immunotherapies. They have a tendency for intramural growth. Associated stones and xanthogranulomatous Other Renal Epithelial Tumors pyelonephritis make detection difficult.At times their imaging appearance mimics a transitional A number of mostly cystic renal neoplasms cell carcinoma. Both local spread and metasta- cause considerable confusion and defy ready sis are common at the initial presentation.As an classification. The traditional method is to example, a man with a destroyed and painful divide them into benign (metanephric kidney containing a staghorn calculus and adenoma, multilocular cystic nephroma, nep- believed to contain pyonephrosis underwent hronogenic nephroma, and congenital mesobla- nephrectomy (72); a renal pelvis squamous cell stic nephroma) and malignant (Wilms’ tumor, carcinoma had invaded the kidney and psoas atypical mesoblastic nephroma, and cystic muscle. partially differentiated nephroblastoma) neo- 627

KIDNEYS AND URETERS plasms, although some defy discrete classifi- kidney contains metanephric tissue, the con- cation. From a radiologic perspective it appears tralateral kidney is at increased risk of contain- more appropriate to classify them into solid and ing a Wilms’ tumor. Persistent metanephric cystic neoplasms and then subdivide by patient tissue is found in a number of syndromes, age (Table 10.7). In addition to the neoplasms including Beckwith-Wiedemann syndrome listed in the table, a multicystic dysplastic (discussed earlier; see Congenital Abnormali- kidney and segmental multicystic dysplasia in a ties, above), Denys-Drash syndrome (gonadal duplicated renal collecting system are also in the dysgenesis, nephropathy, and renal failure), differential diagnosis. Perlman syndrome, hemihypertrophy, neurofi- An association of fetal nephrogenic rests and bromatosis, and sporadic aniridia. Early and multicystic dysplasia has already been dis- often bilateral Wilms’ tumors develop in cussed. Nephrogenic tissue is also associated patients with these syndromes. with some neoplasms; benign ones include Denys-Drash syndrome is caused by a muta- multilocular cystic nephroma and nephrogenic tion in the WT1 gene on chromosome 11p13, a nephroma, and the malignant ones are Wilms’ tumor-suppressor gene. It is highly expressed tumor and mesoblastic nephroma. And then during genital and renal development. Wilms’ there is cystic partially differentiated nephrob- tumors in this syndrome are derived from cells lastoma (discussed below); pathologists usually homozygous for this mutation. classify it as a separate entity, but strong evi- A kidney diffusely affected with nephroblas- dence for this is lacking. tomatosis is enlarged and has a plaque-like or lobular outline. Imaging shows a subcapsular tumor or tumors. Data from the German Nephroblastoma Study Group identified Wilms’Tumor (Nephroblastoma) nephrogenic rests as multinodular, peripheral Nephroblastomatosis cortical lesions, with diffuse extension being less common (73); the rests were homogeneous Persistence of renal blastema tissue in a neonate and hypodense, hypoechoic, and hypointense is known as nephroblastomatosis. While imma- on both T1- and T2-weighted images and were ture metanephric tissue (nephrogenic rests) best seen with postcontrast CT and T1-weighted found in nephroblastomatosis is not intrinsi- MRI. They enhance less post–CT contrast than cally neoplastic, it is believed to be able to do renal parenchyma. Lesions <1cm were rarely undergo neoplastic change, and nephroblas- identified by US. Overall, homogeneity was tomatosis is probably a precursor of Wilms’ the most reliable criterion in differentiating tumors, or at least some of them. If one resected nephrogenic rests from Wilms’ tumors.

Table 10.7. Classification of primary renal neoplasms (by age and solid versus cystic) Age Mostly solid Mostly cystic Neonates Mesoblastic nephroma Cystic mesoblastic nephroma Children Wilms’ tumor (nephroblastoma) Cystic Wilms’ tumor Mesoblastic nephroma Multilocular cystic nephroma Metanephric adenoma Cystic partially differentiated nephroblastoma Chromophobe carcinoma Cystic clear cell sarcoma Duct of Bellini carcinoma Cystic mesoblastic nephroma Cystic renal cell carcinoma Adults Renal cell carcinoma Multilocular cystic nephroma Wilms’ tumor (rare) Cystic renal cell carcinoma Mesoblastic nephroma (rare) Cystic partially differentiated nephroblastoma Metanephric adenoma Cystic Wilms’ tumor (rare) Chromophobe carcinoma Duct of Bellini carcinoma Oncocytoma 628

ADVANCED IMAGING OF THE ABDOMEN

Children Clinical A Wilms’ tumor, or nephroblastoma, is the most common solid abdominal malignancy in child- hood. The vast majority originate in the kidneys, with only an occasional one developing in other extraperitoneal structures, presumably from retained mesonephric tissue. Some are bilateral, with most of these being synchronous rather than metachronous. An occasional Wilms’ tumor first manifests as pulmonary metastases. It is rare in the neonate; neverthe- less, synchronous bilateral Wilms’ tumors in neonates are described. A majority are detected in children below the age of 5 years. Figure 10.25. Anaplastic Wilms’ tumor in a 6-year-old with a An occasional Wilms’ tumor is familial. Chil- palpable abdominal tumor. Computed tomography identifies a dren with hemihypertrophy are at an increased left renal tumor deviating the kidney anterior and medial.A claw risk of having Wilms’ tumor; the risk is about sign suggests the diagnosis. Adenopathy is also present. Other 5%, and these children should undergo serial studies detected pulmonary metastases. (Courtesy of Luann surveys up to about the age of 8 years. The Teschmacher, M.D., University of Rochester.) prevalence of Wilms’ tumors is considerably higher in children with aniridia, who should also undergo serial surveillance. An occasional distorting adjacent renal parenchyma (Fig. Wilms’ tumor develops in a setting of cryp- 10.25). Some are mostly exophytic. Necrosis is torchidism. A number of chromosome abnor- common. An occasional Wilms’ tumor contains malities are evident in some of these patients, fat or calcifications, although in general calci- including a Wilms’ tumor-suppressor gene at fications in a juxtarenal tumor in a child should 11p13. suggest a neuroblastoma. A minority of these tumors contain bone, car- Postcontrast CT and nonenhanced MRI tilage, fat, or other atypical tissue. Some investi- appear equally accurate in establishing size and gators label these as “teratoid Wilms’” tumors. tumor origin, although both are inaccurate in Some such teratoid Wilms’ tumors contain a staging. Ultrasonography can assess tumor size cystic component. but not origin. Ultrasonography most often A palpable abdominal tumor is a common identifies a large, well-marginated tumor of presentation. Bleeding develops in some heterogeneous, increased echogenicity due to tumors and they enlarge suddenly due to hem- necrosis and hemorrhage. Possible renal vein orrhage. A hematoma or urinoma is not an and inferior vena caval invasion is evaluated uncommon association. Renin is produced with Doppler US. by a minority and these children develop Magnetic resonance typically reveals these hypertension. tumor to be hypointense on T1- and hyper- These tumors spread hematogenously to intense on T2-weighted images. Larger ones lungs, liver, bone, and other organs. The overall often contain blood and are heterogeneous in prognosis (long-term cure) in children with appearance. Their postcontrast enhancement is Wilms’ tumors is approximately 80%. variable. Ultrasonography-guided needle biopsies of Renal vein invasion is common, and some pediatric renal tumors, including Wilms’ extend into the inferior vena cava; and an occa- tumors, have been safely performed, although sional one even grows into the right atrium the technique is controversial. (Fig. 10.26). A tumor thrombus extending into the left renal vein can obstruct the gonadal vein Imaging and result in a varicocele. Ultrasonography should identify most such tumor extensions. Typically, when first detected these are large, Aortic encasement is uncommon. These tumors round, soft tissue tumors infiltrating and also grow into the calyces and adjacent ureter. 629

KIDNEYS AND URETERS

A B

Figure 10.26. Wilms’ tumor. A: T2–weighted transverse MR image identifies a right renal tumor (arrows) with extension into the renal vein (arrowhead). B: Coronal T1-weighted image shows tumor extension into the vena cava (arrow). (Source: Burgener FA, Meyers SP,Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.)

A rare one even extends intraluminally in the Follow-up of the remaining kidney in chil- ureter. dren after unilateral nephrectomy for Wilms’ A rare Wilms’ tumor is multicystic and tumor reveals that only half develop renal mimics a multilocular cystic nephroma hypertrophy. or benign renal cystic disease. Likewise, differentiation from a neuroblastoma can be Adults difficult, although a neuroblastoma tends to be ill-defined and more heterogeneous in appear- A Wilms’ tumor is rare in adults. Histologically, ance. Also, a neuroblastoma tends to metasta- these tumors are similar to the ones seen in chil- size early and extensively. Superficially, a Wilms’ dren, and the therapy likewise is similar, but tumor can be confused with xanthogranuloma- these tumors grow rapidly and prognosis is tous pyelonephritis. worse than in children, possibly due to their more advanced presentation. Even extrarenal Therapy and Outcome Wilms’ tumors have developed in adults (76). A typical Wilms’ tumor in an adult consists of Bilateral Wilms’ tumors present a therapeutic a complex mass often containing a cystic com- dilemma. Conservative surgical therapy with ponent. These tend to be large, hypovascular initial biopsy followed by chemotherapy and and multilocular tumors containing a limited delayed tumor resection in children with bilat- solid component. The differential includes a eral Wilms’ tumors in the United Kingdom Chil- cystic carcinoma and a multilocular cystic dren’s Cancer Study Group resulted in a mean nephroma. preserved renal mass of 45%, but initial surgi- cal resection followed by chemotherapy left a renal mass of 35% (74); children in both groups Multilocular Cystic Nephroma/Cystic had similar survival and similar renal function. Partially Differentiated Nephroblastoma Imaging after chemotherapy usually identi- Clinical fies necrosis, hemorrhage and calcifications. In one child CT after chemotherapy showed an These tumors consist of a mixture of epithelial increase in tumor size and extensive fatty and mesenchymal components. In the past, a infiltration (75); resection revealed no residual multilocular cystic nephroma, also called multi- blastema. cystic nephroma, cystic lymphangioma,and 630

ADVANCED IMAGING OF THE ABDOMEN multilocular cyst, was considered a hamartoma, solid component, and the presence of a solid although the current thinking leans toward a component should suggest either malignant neoplastic origin. Some authors classify multi- transformation or another diagnosis. locular cystic nephroma and cystic partially dif- Magnetic resonance imaging of a multilocu- ferentiated nephroblastoma in young children lar cystic nephroma reveals a complex solitary as one entity and believe that they represent renal cystic tumor often protruding into the cystic Wilms’ tumors having little potential for renal collecting system and containing thin invasion or metastasis (77); in adults, however, septa, with the cystic component varying from these authors believe that multilocular cystic hypo- to hyperintense on T1-weighted images. nephroma is a separate benign entity inde- Any solid component and septa enhance post- pendent of Wilms’ tumor, although a rare one contrast in all cases. does undergo malignant transformation and Nephrectomy in a patient with a multilocular develops into a carcinoma or sarcoma. In one cystic nephroma should be curative. With a adult, a cystic partially differentiated nephrob- cystic partially differentiated nephroblastoma, lastoma exhibited cell maturation intermediate however, some tumors recur locally. between a multilocular cystic nephroma and a Wilms’ tumor (78). Metanephric (Embryonal) Adenoma A similar condition is found in some infants with other gastrointestinal and skeletal abnor- A curious tumor composed of small tubular, malities,including visceromegaly (Perlman syn- papillary, and glomeruloid structures and con- drome), an autosomal-recessive condition. sisting of proliferating primitive epithelial cells In children (mostly young boys) a multilocu- mimicking an embryonal nephron was first lar cystic nephroma is radiographically and described in 1980 and called a nephronogenic grossly indistinguishable from a cystic partially nephroma (79). Later, a similar benign mixed differentiated nephroblastoma. Both are cystic epithelial and mesenchymal renal tumor was thin-walled tumors containing multiple septa- termed an embryonal adenoma. Since then, a tions surrounded by a fibrous capsule. These number of reports have used the term tumors differ histologically in that a multilocu- metanephric adenoma. Whether this tumor lar cystic nephroma is composed of mature represents a benign counterpart of Wilms’ differentiated tissue and does not contain tumor is conjecture. Metanephric adenomas blastemal elements, while septa in a cystic par- and metanephric adenofibromas (discussed tially differentiated nephroblastoma do contain below) are closely related neoplasms. In either embryonal cells. Calcifications are uncommon case, a renal metanephric adenoma is a distinc- in children. tive renal cortical neoplasm usually classified among nephroblastic tumors. Its histologic Imaging appearance is similar to that of metanephric hamartomas found in nephroblastomatosis. Imaging detects both of these cystic tumors In spite of a morphologic similarity to Wilms’ but cannot differentiate between them. Their tumor, genetics suggest a relationship to appearance is similar to other cystic tumors. papillary adenomas and papillary renal cell They occur unilaterally. In children, the numer- carcinomas. ous small cysts can appear solid, and imaging These tumors consist of differentiated cells findings resemble a Wilms’ tumor. In adults containing few or absent mitoses; tubules and (mostly women), imaging and even aspiration glomeruli are often identified. Its metanephric biopsy findings mimic a cystic renal cell carci- (embryonic) architectural and cytologic noma, although these tumors are not related. appearance is characteristic, although patho- Computed tomography reveals multilocular logic study of some tumors suggests a malig- cystic nephromas to be homogeneous, multi- nancy. Needle biopsy and aspiration cytology cystic tumors containing thin septa without a specimens have been misdiagnosed as Wilms’ solid components; for some reason a lower pole tumor. The reverse is also true: a renal cell location predominates. The cystic component carcinoma and a metastasis from a poorly dif- does not enhance with contrast. Their hallmark ferentiated thyroid carcinoma can be misdiag- is that septa tend to be their only prominent nosed as metanephric adenomas. Most authors 631

KIDNEYS AND URETERS consider these tumors to be benign, although a Histology reveals onion-skin cuffing around metanephric adenoma in a 7-year-old girl entrapped renal tubules, heterologous glial or metastasized to lymph nodes (80). cartilage differentiation, and vascular changes There are two age peaks; half occur in chil- consisting of angiodysplasia of entrapped arte- dren and the other half mostly in women in rioles and juxtaglomerular cell hyperplasia of their 50s. Most tumors are discovered inciden- entrapped glomeruli (82). tally, with only a minority of patients having The mean age of 31 patients with a pain, hematuria, or a palpable tumor. Poly- metanephric stromal tumors was 2 years; most cythemia and acquired von Willebrand’s disease tumors presented as an abdominal tumor (82); develop in some patients. An association of a they did not metastasize. The differential diag- metanephric adenoma with embryonal hyper- nosis includes renal clear cell sarcoma. plasia of Bowman’s capsular epithelium was reported in a 9-year-old boy on peritoneal dialysis (81). Mesoblastic Nephroma (Bolande’s Tumor) Metanephric adenomas are well-circum- Infants scribed, unencapsulated tumors varying in size. Some contain fibrosis and calcifications. Com- Congenital mesoblastic nephroma, at times puted tomography, US, and MRI usually reveal called congenital Wilms’ tumor, comprises about a solid tumor with occasional necrosis and half of renal tumors encountered during the cystic degeneration, suggestive of a hypovascu- neonatal period. Most occur within the first lar renal cell carcinoma. They are iso- to hyper- month of life, and their prevalence decreases dense on CT. They range from hypo- to during childhood. They present as a large hyperechoic on US. abdominal tumor. The prognosis depends on Simple resection is curative in almost all the infant’s age, being best for tumors discov- patients. ered early in life. Earlier publications considered mesoblastic Metanephric (Nephrogenic) Adenofibroma nephromas to be a benign neoplasm, possibly even hamartomatous in origin. In fact, the The histology of metanephric adenofibromas favorable prognosis of Wilms’ tumors in (previously also called nephrogenic adenofi- neonates reported previously is suspect because bromas) reveals a proliferation of spindle cells, many of these were probably mesoblastic similar to what is found in congenital mesoblas- nephromas rather than Wilms’ tumors. tic nephroma, encasing nodules of embryonal The morphologic and cytogenetic evidence epithelium similar to the nephroblastomatosis suggests a relationship between congenital associated with Wilms’ tumor; it is thus not mesoblastic nephromas and infantile fibrosar- surprising that these tumors have been misdi- comas. Not only are these tumors similar his- agnosed as Wilms’ tumors and mesoblastic tologically, but also both are associated with nephromas. similar chromosome polysomies and they may These are childhood tumors. A not uncom- represent a single entity. Congenital mesoblas- mon presentation is hematuria, hypertension, tic nephromas and Wilms’ tumors also appear or polycythemia. to share common genetic pathways and abnormalities. Metanephric Stromal Tumor Mesoblastic nephromas are mostly solid tumors which usually follow a benign course A metanephric stromal tumor is a renal but tend to invade adjacent structures. Some medullary spindle cell (fibrous) tumor contain- authors subdivide these tumors into congenital ing smooth-walled cysts that entrap native and atypical, with the latter including aggressive kidney tissue. Although such a description sug- and potentially malignant variants. The aggres- gests that it should be classified under mes- sive variety tends to recur or metastasize. A enchymal tumors, it is histologically identical rare aggressive mesoblastic nephroma ruptures to the stromal component of metanephric spontaneously. adenofibroma and is discussed with the latter Imaging reveals a solid, homogeneous, entity (see above). usually large tumor. Hemorrhage and necrosis 632

ADVANCED IMAGING OF THE ABDOMEN develop in the aggressive and malignant solitary to multiple tumors, diffuse infiltration, variants, although cystic degeneration is not or invasion from adjacent structures. Even common. Their imaging appearance mimics a perirenal involvement varies considerably Wilms’ tumor. from focal tumors to plaque-like infiltration. Some mesoblastic nephromas show uptake of Retroperitoneal lymphoma generally invades Tc-99m-DMSA. the kidneys through renal sinuses, and thus the renal medulla is more often involved than the cortex. Adults Necrosis is uncommon in renal lymphomas, The rare similar adult renal tumor consisting even when large. Likewise, lymphoma rarely of epithelial and stromal tissue is probably results in a vascular tumor thrombus. a different entity than the pediatric variety. Computed tomography findings in the rare Immunohistochemistry and electron micro- primary non-Hodgkin’s renal lymphoma range scopy aid in identifying this tumor. Some from a single nodule, multiple nodules, and mesoblastic nephromas in adults may represent diffuse infiltration, to a lymphomatous mass cystic hamartomas. An adult mesoblastic encasing the kidney. Lymphomatous foci are nephroma can grow either intra- or predomi- homogeneous and mostly slightly hyperdense nantly extrarenal, at times even mimicking an to isodense on precontrast CT and do not adrenal tumor. enhance as much as normal renal parenchyma postcontrast. Focal tumors maintain a dis- crete margin. Diffuse infiltration results in an Lymphoma/Leukemia overall renal structure disorganization. A not unusual appearance is renal invasion by Clinical retroperitoneal lymphoma, but the lack of adja- cent adenopathy is unreliable in excluding lym- True lymphatics are not present in the kidneys phoma. While CT allows evaluation of the site and primary renal lymphoma is rare. Secondary and size of involvement, it cannot establish a involvement is either via contiguous spread diagnosis; similar findings are seen with a from perirenal disease or from hematoge- renal cell carcinoma, transitional cell carci- nous dissemination. Involvement with non- noma, metastatic disease, or even some chronic Hodgkin’s lymphoma is considerably more inflammatory conditions. common than Hodgkin’s lymphoma. Kidneys Two sonographic patterns are evident: either of immune-deficient patients are more prone a bilateral nodular infiltrate or diffuse renal to involvement by lymphoma. Infiltration is enlargement with loss of differentiation be- usually bilateral. tween renal sinus echoes and parenchyma. The Lymphoma involvement in other locations typical infiltration is hypoechoic, but at tends to dominate the clinical findings. Most times homogeneous involvement results in an renal involvement does not lead to symptoms anechoic pattern mimicking a cyst. until late in the course. A rare presentation is Magnetic resonance imaging shows iso- or acute renal failure. slight hypointense tumors on T1- and A granulocytic sarcoma (also called a hypointense tumors on T2-weighted images. chloroma) develops in a minority of patients Postcontrast lymphomas show minimal tumor after therapy for some leukemias. These solid enhancement, in distinction to renal cell carci- renal tumors are hypointense on T1- and hyper- nomas where early enhancement is common. intense on T2-weighted images. They show little Whether CT or MR is superior in identifying contrast enhancement. and defining lymphomatous involvement is not clear. Ureteral involvement consists either of Imaging encasement or displacement by an adjacent lymphomatous focus. Imaging detects only a minority of lymphoma- Leukemic involvement results in symmetri- tous renal involvement. No typical pattern pre- cally enlarged kidneys and compressed collect- dominates, and renal lymphoma ranges from ing systems. 633

KIDNEYS AND URETERS

Multiple Myeloma Renal histology in patients with myeloma nephropathy revealed 14% with tubulointersti- tial nephritis, 11% with amyloidosis, 7% with acute tubular necrosis, and 4% each with nodular glomerulosclerosis and plasma cell infiltration (83); at times renal biopsy pro-vides the first clue to a diagnosis of myeloma by iden- tifying myeloma cast nephropathy. Tubular precipitation of Bence-Jones proteins is a cause of renal failure in multiple myeloma patients. Haphazard IV contrast injection is a cause of such precipitation, but with preplan- Figure 10.27. Renal angiomyolipomas in a 17-year-old with ning and adequate hydration a number of these tuberous sclerosis. The left fat-containing tumor is obvious. A patients have undergone contrast studies smaller angiomyolipoma is also present in the right kidney without complication. (arrow). (Courtesy of Luann Teschmacher, M.D., University of Resorption of calcium from bone and the Rochester.) resultant hypercalcemia lead to nephrocalci- nosis. The kidneys enlarge, and the collecting systems are compressed. These patients are also prone to developing uric acid calculi. oleiomyomatosis, and tumors at other sites, but Unexplained renal failure in a patient even in general extrarenal angiomyolipomas are rare. with absent skeletal lesions can still be due to These tumors develop in the renal capsule, multiple myeloma. cortex, and medulla. Histologically they are composed of haphazardly arranged blood Mesenchymal Neoplasms vessels, disorganized smooth muscle fibers, and varying amounts of fat. Some contain sheets of Angiomyolipoma epithelioid cells,suggesting a malignancy.Those without fat mimic a leiomyoma. Histologically, Clinical no sarcomatous transformation should be Classification of angiomyolipomas has evolved evident in either the leiomyomatous or from their being considered hamartomas to lipomatous components. benign neoplasms, although a rare one does Serial CT and US provide a measure of renal undergo sarcomatous transformation and a angiomyolipoma growth rates. The mean propensity to metastasize. Even the usually growth rate of isolated tumors is about 5% per benign variety tends to be locally aggressive and year, being considerably more in those with produces considerable mischief. In some studies tuberous sclerosis. No correlation exists 20% to 50% are detected in tuberous sclerosis between the amount of fat in a tumor and its patients, where they tend to be multiple and growth rate. Growth tends to be unpredictable. bilateral. Angiomyolipomas are associated to a Some tumors are stable for years and then lesser degree with von Recklinghausen’s disease, undergo a fast increase in size, followed by von Hippel-Lindau disease, and adult polycystic another period of quiescence. Rapid growth disease, and are found in about half of patients occasionally occurs in pregnancy, suggesting with pulmonary lymphangiomyomatosis. In that hormones play a role in their growth. An general, a finding of multiple angiomyolipomas occasional angiomyolipoma is huge at initial should suggest tuberous sclerosis (Fig. 10.27). presentation. In tuberous sclerosis, angiomyolipomas occur Spontaneous, solitary tumors are most earlier in life than sporadic ones, and most common in middle-aged women and are rare in are discovered incidentally. An occasional children. Pain, a palpable tumor, or hematuria is tuberous sclerosis patient develops bilateral a common presentation, although many of these renal angiomyolipomas,pulmonary lymphangi- tumors are asymptomatic. 634

ADVANCED IMAGING OF THE ABDOMEN

Pathologists describe a rare epithelioid Even when associated with fat, calcifications angiomyolipoma as a separate entity. It tends to should suggest a carcinoma. mimic renal cell carcinoma; it contains regions Diagnostic difficulty occurs when a tumor is of hemorrhage and necrosis. Fatty tissue is not small or contains very little fat. Conventional CT identified. may not detect fat in tumors smaller than The rare liposarcoma is indistinguishable several centimeters in size. Multislice helical CT with imaging from an angiomyolipoma. This is more sensitive and is preferred for small problem is especially pertinent when an inci- lesions. These low-fat tumors are homoge- dental renal angiomyolipoma is detected in the neously hyperdense on unenhanced CT, show work-up of another carcinoma and a metastatic homogeneous postcontrast CT enhancement, liposarcoma is suspected. and are isoechoic on US. Recent hemorrhage tends to mask any fatty component. Occasion- Imaging ally in such tumors a small amount of fat is detected with chemical shift MRI but not CT; in Angiomyolipomas are diagnosed with CT, US, these, a renal cell carcinoma is in the differen- or MR (Figs. 10.28 and 10.29); most contain tial diagnosis. sufficient focal fat to be identified with CT, The diagnosis appears more difficult in chil- appear as homogeneous and hyperechoic dren. Some of these tumors in children contain tumors containing smooth margins with US, little fat and imaging simply identifies a large and have hyperintense signals on T1- and renal tumor. Even a fine needle biopsy may be hypointense signals on T2-weighted MRI. misleading and a Wilms’ tumor initially sus- Focal fat is also found in lipomas and some pected. The reverse is also true; US detection of liposarcomas, but these tumors are rare in the a hyperechoic tumor in a child with von Hippel- kidneys. Clear cell renal cell carcinomas contain Lindau disease suggests an angiomyolipoma, intracellular lipid and glycogen, which is yet an occasional such tumor is a renal cell detectable with chemical shift MR, but this fat carcinoma. is diffuse. Focal regions of fat are rare in renal A CT diagnosis is straightforward with most cell carcinomas. angiomyolipomas. Fat intermixed with other Calcifications are not a feature of angio- tissue detected on thin-section nonenhanced myolipomas except secondary to hemorrhage. CT is strong presumptive evidence for an

A

Figure 10.28. Right renal angiomyolipoma.A: CT identifies a fat- containing tumor in the superior renal pole (arrow). B: Selective angiography shows a poorly vascular tumor that was sub- sequently embolized. (Courtesy of David Waldman, M.D., University of Rochester.) B 635

KIDNEYS AND URETERS

A B

C D Figure 10.29. Angiomyolipoma with a retroperitoneal bleed.A: CT reveals a fat-containing left renal tumor (arrows).Arterial-phase (B) and delayed-phase (C) arteriography also identify the tumor but did not detect a site of bleeding. D: An inferior vena cavagram study reveals caval compression from the left side by the extensive retroperitoneal bleeding (arrow). (Courtesy of Oscar Gutierrez, M.D., University of Chile, Santiago, Chile.)

angiomyolipoma. Precontrast CT should be With an atypical CT appearance aspiration used; postcontrast enhancement may increase biopsy or cytology should provide a definitive the density to the level of water. Angiomyolipo- diagnosis. mas tend to be well marginated but do not have A typical sonographic appearance of an a capsule. Cystic regions are not common. angiomyolipoma is that of a well-circum- Larger tumors often extend outside the kidney. scribed, homogeneous, hyperechoic tumor. 636

ADVANCED IMAGING OF THE ABDOMEN

Shadowing is detected in some, a finding mas using a combination of sequences. Thus unusual for a carcinoma. Because many small in-phase sequences show them to be minimally renal cell carcinomas are also hyperechoic, it is or moderately hyperintense relative to the renal necessary to confirm US findings with other cortex, and fat-suppressed sequences reveal a imaging. In some instances, however, a homo- loss of signal intensity (84). Some tumors geneously hyperechoic lesion is accepted are difficult to identify due to limited signal without confirmation as a probable angiomy- differences or breathing artifacts. olipoma, especially in patients under the age of 50 and with a tumor smaller than 15mm or Complications possibly 10mm in diameter. In some patients with tuberous sclerosis and a confluence of mul- Complications include compression of adjacent tiple angiomyolipomas, US simply reveals dif- calyces and intratumoral, subcapsular, perire- fusely increased echogenicity in markedly nal, or pararenal bleeding and hematoma (Fig. enlarged kidneys. 10.30). These tumors undergo cystic degenera- Ultrasonography frequency-dependent atte- tion. Spontaneous rupture is not uncommon nuation is potentially useful in differentiating and an angiomyolipoma should be high in the renal cell carcinomas from angiomyolipomas. differential for the patient presenting with Frequency-dependent attenuation values of spontaneous rupture and bleeding of a renal renal cell carcinomas are significantly lower tumor. than those of angiomyolipomas. Some overlap Extrarenal extension into the perirenal fat does exist, and the practical application of this and lymph nodes is common, and these technique remains to be established. enlarged pararenal lymph nodes cause addi- The fat component even in small tumors is tional diagnostic and therapeutic dilemmas. identified by fat-suppressed T1-weighted MRI. Computed tomography shows these enlarged Fat in these tumors tends to be scattered lymph nodes to be of soft tissue density, throughout the lesion. Opposed phase MRI although an occasional one contains fat. alone, being sensitive even to intracytoplasmic Extension into a renal vein and inferior lipid found in some renal cell carcinomas, is vena cava as a tumor thrombus represents an inappropriate to evaluate the gross fat in additional complication. Computed tomogra- angiomyolipomas and differentiate them from phy can occasionally detect fat within a throm- carcinomas. Magnetic resonance imaging can bus.Renal vein involvement is more common on reliably identify small (<1.5cm) angiomyolipo- the right and does not necessarily imply malig-

A B

Figure 10.30. Bleeding left renal angiomyolipoma. Noncontrast CT reveals a fat-containing left renal tumor (A, arrow), surrounded by a well-marginated infiltrate having a CT density similar to aorta (B). (Courtesy of Algidas Basevicius, M.D., Kaunas Medical University, Kaunas, Lithuania.) 637

KIDNEYS AND URETERS nant transformation. Complicating matters, an calcifications. Computed tomography and US occasional one is associated with a renal cell reveal a heterogeneous and hypoechoic tumor. carcinoma. Imaging shows most sarcomas as large, invasive, necrotic tumors. They tend to mimic a Therapy large renal cell carcinoma. Poorly defined calcifications are seen in a minority. Metastases Many of these tumors are still treated with a at initial presentation are common. nephrectomy, although a trend is toward a more conservative approach—partial nephrectomy or enucleation is feasible in some patients. Angiomatous Neoplasms Incomplete tumor excision, however, leads to A primary renal angiosarcoma is very rare, with recurrence, often rapidly. only case reports described. They are also In patients with tuberous sclerosis, emboliza- known as a malignant hemangioendothelioma, tion is effective in long-term management of hemangioendothelial sarcoma,and vascular hemorrhage; most of these patients require sarcoma and appear as single or multiple several embolization sessions. If needed, a tumors. They arise from blood vessel endothe- partial nephrectomy is then performed. lial cells. Hemorrhage is a common presenta- Symptomatic renal angiomyolipomas have tion. Some contain fat cells suggesting an been embolized with a mixture of iodized oil angiomyolipoma. and absolute ethanol (85); some tumors An epithelioid angiosarcoma is a very aggres- decrease in size and others do not change, but sive tumor mimicking a primary epithelial most patients remain asymptomatic (except tumor. with incomplete embolization). Follow-up after embolization reveals that it is the angiomyo- genic components that disappear, while fatty Clear Cell Sarcoma tissue undergoes liquefactive necrosis. Clear cell sarcomas are rare tumors found in younger children. Initially thought to be a Lymphangiomyoma variant of Wilms’ tumor, this tumor has distinct Lymphangiomyomas, considered to be hamar- immunohistochemical and flow cytometric tomas rather than neoplasms by some authors, findings differing from Wilms’ tumors. Its rela- are discussed in more detail in Chapter 14. tionship to mesoblastic nephroma is not clear. Lymphangiomyomas are related to angiomyo- Clear cell sarcomas exhibit p53 protein nuclear lipomas and are occasionally associated with an immunopositivity, suggesting alterations in the angiomyolipoma; they are also suspected of p53 tumor-suppressor gene. being a manifestation of tuberous sclerosis. The imaging findings of clear cell sarcomas One cause of chyluria is renal or retroperi- are similar to those of a Wilms’ tumor, with toneal lymphangioleiomyomatosis. differentiation made by histology. These are cystic, hypervascular lesions, This is an aggressive tumor having a readily confused with renal cell carcinomas. poor prognosis and a predilection for bone metastasis. Leiomyomatous Neoplasms Ossifying Renal Tumor of Infancy Leiomyosarcomas account for half or more of the rare renal sarcomas. Even after resection, The few reported ossifying renal tumors of differentiation between a leiomyoma and its infancy occurred in infants under the age of 14 malignant counterpart is difficult. These tumors months. They appear to be benign. These originate mostly from blood vessels, although tumors contain varying proportions of osteoid, some of the reported renal leiomyomas prob- osteoblastic cells, and spindle cells. Whether the ably represent atypical angiomyolipomas. osteoid component represents a form of urothe- Most benign leiomyomatous tumors are solid lial transformation is speculation. The propor- and well marginated, but degeneration leads to tion of osteoid and the degree of osseous a cystic appearance. An occasional one contains maturation increases with age. 638

ADVANCED IMAGING OF THE ABDOMEN

Gross hematuria is the most common tension, which can be severe, often associated presentation.An occasional infant presents with with hypokalemia and hyperaldosteronism. An a palpable abdominal mass. occasional incidentally discovered reninoma is Typically these tumors are attached to a renal nonfunctioning. As its name implies, these papilla and present as a pelvicalyceal system tumors originate from juxtaglomerular cells. tumor. Some resemble a staghorn calculus. Whether they are hamartomas or neoplasms is not established. They are benign. Histologically, Osteogenic Sarcoma some of these tumors mimic a hemangioperi- cytoma, with the latter tumor occasionally also A primary renal osteogenic sarcoma is very rare resulting in hypertension. and should be distinguished from a sarcoma- These are solid, hypovascular tumors on CT toid variant of renal cell carcinoma with osteoid and hyperechoic on US. Most reninomas are formation. Whether these tumors represent a smaller than 2 to 3cm in diameter. Even if a sarcomatous version of an angiomyolipoma is reninoma is too small to be detected with speculation. imaging, with strong clinical suspicion renal Patients with a primary renal osteogenic vein catheterization and renin-level sampling sarcoma have elevated serum alkaline phos- should suggest a tumor site. It should be kept in phatase levels but no underlying bone disease. mind, however, that some renal cell carcinomas These tumors contain calcifications. A “sun- and other renal tumors on occasion also burst” type of calcification, if present, should produce renin. suggest the diagnosis. The differential diagnosis Resection leads to a marked drop in blood for a calcified renal tumor includes a calcified pressure in most but not all patients, with the inflammatory tumor, renal cell carcinoma, and latter presumably having a residual angiopathy. a metastatic or invading osteogenic sarcoma. Hemangiopericytoma Histiocytoma Hemangiopericytomas are rare in the kidneys. A majority of renal histiocytomas are malig- An occasional one leads to hypertension. These nant. A renal capsule origin is common. A are well-marginated, solid, hypovascular renal review of 44 malignant renal fibrous histiocy- sinus tumors involving the renal hilum to the tomas found an average patient age of 58 years, point of suggesting a renal pelvis transitional no sex predilection, and two thirds of tumors cell carcinoma.Some are large at the initial pres- involving the left kidney (86). Symptoms tend to entation, compressing the renal pelvis and be few, and a late presentation is common. causing hydronephrosis and parenchymal Sudden flank pain suggests spontaneous tumor atrophy. rupture. Needle aspiration cytology may suggest the Imaging reveals a solid tumor tending to be diagnosis, although the appearance is similar to hypodense on CT, hypoechoic on US, and that seen with other spindle cell tumors. hypovascular on angiography (86). A correct Immunohistochemistry is helpful. preoperative diagnosis is not common, with renal cell carcinoma or oncocytoma often being Renal Capsule Neoplasms suspected. These tumors have a poor prognosis. Metas- Neoplasms originating from the renal capsule tases and local recurrence after resection are are not common. They represent a spectrum common. of mesenchymal origin, with some earlier authors simply referring to them as capsulomas. Reninoma (Juxtaglomerular Tumor) They include a histiocytoma, solitary fibrous tumor, leiomyoma, lipoma, and even an These rare renin-secreting tumors, known as angiomyolipoma, the latter a rare site for this reninomas and juxtaglomerular cell tumors, tumor. Differentiating capsular from renal and occur both in children and adults and are more extraperitoneal origin tumors is often difficult, common in females. Their primary importance especially with larger ones. Identifying a capsu- is their renin production and resultant hyper- lar artery by angiography as a primary tumor 639

KIDNEYS AND URETERS feeding artery is helpful. Depending on the type outline. A renal tumor in a patient with wide- of tumor, the adjacent renal parenchyma is spread metastases is most likely metastatic. either compressed or invaded. Often a renal cell Computed tomography often reveals smaller carcinoma or oncocytoma is suspected. and more numerous metastases than US; most Multiple renal capsular leiomyomas have are hypodense and inhomogeneous on precon- been reported. trast CT, while postcontrast CT reveals most to have inhomogeneous enhancement. Most Other Tumors enhance less than normal renal parenchyma. Metastatic thyroid carcinomas, on the other Although a renomedullary interstitial tumor hand, tend to be hyperdense and have variable (previously called medullary fibroma) is contrast enhancement. Renal vein invasion is detected in 26% to 41% of autopsies (87), the rare with metastatic disease. majority are only several millimeters in diame- The sonographic appearance of metastases ter and not detected by imaging. One did not varies; they range considerably in their homo- enhance by CT, was hypointense both on T1- geneity. Most are hypoechoic, although some, and T2-weighted images, and arteriography such as thyroid carcinomas, are hyperechoic or revealed no neovascularity (87). even isoechoic. A normal kidney does not contain fat, and Metastasis from a hepatocellular carcinoma only limited case reports of renal lipomas are tends to mimic a renal cell carcinoma with both published. They predominate in women. imaging and even needle biopsy. A metastatic ovarian or appendiceal cystade- Metastases nocarcinoma presents as a cystic tumor. Renal Ureteral Metastases to the kidneys are common, with Metastases to the ureter can generally be multiple foci and bilateral involvement typical. divided into those from a pelvic cancer and Problems arise when there is a single renal those extrapelvic in origin. tumor in a patient with a history of a malig- A carcinoma metastatic to the periureteral nancy. Is this an isolated metastasis or a second region obstructs the ureter and the patient pres- primary, such as a renal cell carcinoma? Occa- ents with flank pain and urinary tract infection. sionally even an abscess mimics a neoplasm. One conservative approach in patients with The distinction influences subsequent patient metastatic disease is US to monitor for management, and in such a scenario a renal hydronephrosis. biopsy is often necessary. Drainage of ureteral obstruction due to pelvic Most renal malignant melanomas represent or extrapelvic cancer with double-J catheters metastases, but a rare melanoma believed to has a relatively high success rate; if necessary, a be primary to the kidney has been reported percutaneous nephrostomy is performed. (88). Self-expandable Wallstents have had limited Symptoms related to a primary tumor often acceptance in bypassing malignant ureteral overshadow those due to renal involvement. A obstructions. Patient survival is generally patient occasionally presents with acute renal related to the primary tumor and not to stent failure due to diffuse metastases, but more placement. common are silent metastases. Hematuria and proteinuria develop eventually but renal func- Rhabdoid Tumor tion tends to be preserved until a marked tumor load develops. In a number of these patients a Malignant rhabdoid tumors were initially search for renal metastases is more an academic thought to be a variant of Wilms’ tumor but cur- exercise than a practical endeavor. rently are believed to represent a distinct clini- Many renal metastases have a CT, US, and copathologic entity. An occasional rhabdoid MRI appearance similar to that of renal cell car- tumor develops at an extrarenal site. In the cinoma or lymphoma, although metastases tend kidney it is a highly malignant neoplasm occur- to be small, multiple, and not deform the renal ring most often in infants, less often in young 640

ADVANCED IMAGING OF THE ABDOMEN children. Curiously, about half of these tumors Neurilemoma (Schwannoma) have an associated primary or metastatic central nervous system tumor. A neurilemoma originates from neural This is a solid renal hilum tumor. A CT Schwann cells and is rare in the kidneys. It finding of a heterogeneous tumor, together with has no specific imaging findings. Some extra- a peripheral eccentric crescent having an atten- peritoneal ones simply surround and obstruct uation of fluid, representing subcapsular hem- the ureter or ureteropelvic junction. orrhage or peripheral tumor necrosis adjacent Wide excision is the treatment of choice, to tumor lobules, is common with these tumors. because up to one third are malignant. They can Some contain calcifications outlining tumor recur locally or metastasize. lobules. These findings are not pathognomonic, however, and are seen with other renal neo- Carcinoid Tumor plasms in children. A Wilms’ tumor is generally in the differential diagnosis—the distinction is Primary renal carcinoid tumors are rare. These important because of the considerably better tend to be solid, with an occasional one con- prognosis with a Wilms’ tumor. taining calcifications. An occasional one origi- nates from a cyst wall. For some reason renal carcinoids are more common in horseshoe Small Cell Carcinoma kidneys (89), developing even in a horseshoe kidney isthmus. The descriptive term small cell tumor is Some larger carcinoids undergo hemorrhagic applied to a group of neoplasms having similar necrosis. morphologic characteristics. These include lymphomas and various neuroendocrine carci- nomas. Nonneuroendocrine small cell carcino- mas, also called nonfunctioning neuroendocrine Dilated Urinary Tract carcinomas or simply small cell carcinomas,are very rare in the kidneys and ureters. Some Renal collecting system dilation, or hydro- contain hyperchromatic small cells with neuro- nephrosis, can be secondary to obstruction or secretory granules. Others combine features functional in nature. Hydronephrosis varies with a transitional cell carcinoma, and still from barely discernible to gigantic. At times others exhibit adenomatous or squamous huge hydronephrosis displaces the kidney away differentiation. from its usual location. Complicating the issue, These are very malignant tumors with metas- an occasional patient has intermittent hydro- tases common at the initial presentation. Often nephrosis and, when asymptomatic, IV urogra- metastases are discovered first. phy or US reveal only mild renal pelvic dilatation at best. These patients should thus be studied when symptomatic. Neuroendocrine Tumors An occasional malignant primitive renal neu- Urinary Obstruction roectodermal tumor is encountered that cannot be readily classified. General A possible relationship between H2 receptor The etiologies for urinary tract obstruction antagonist therapy and neuroendocrine carci- range from intrinsic to the urinary tract to nomas is suggested. extrinsic, benign conditions to a malignancy. Some unilateral urinary obstructions are insid- Neuroblastoma ious, and renal function is lost before damage is clinically suspected. As an example, in a patient Most neuroblastomas originate in the adrenal with terminal ileal Crohn’s disease, a surround- glands (discussed in Chapter 16). They occur ing inflammatory mass (phlegmon) can involve primarily in the young and often are in the and obstruct the right ureter and lead to irre- differential diagnosis of a renal or suprarenal versible loss of renal function before damage is tumor. detected. 641

KIDNEYS AND URETERS

In general, with unilateral ureteral obstruc- dilated gonadal vein mimics the appearance of tion at an early age, ipsilateral kidney growth is a dilated ureter. impaired while the contralateral kidney under- In a majority of patients with acute renal goes compensatory growth. This association obstruction, unenhanced helical CT reveals that of ureteral obstruction and subsequent renal an obstructed kidney is less dense than the con- growth retardation is probably mediated by tralateral unobstructed kidney (90); this differ- complex regulation of cell proliferation, ence is visually detected and constitutes a destruction, and other factors. secondary sign for acute obstruction. Urinary perforation proximal to an obstruc- Gray-scale US readily detects moderate tion is generally secondary to an acute obstruc- hydronephrosis as an anechoic region conform- tion, typically a stone. An occasional neoplasm, ing to the renal collecting system. Mild such as a transitional cell carcinoma, not only hydronephrosis can be confused with promi- obstructs the urinary tract but also weakens the nent renal veins; Doppler US is helpful in this ureteral wall sufficiently to produce rupture, setting. Determining whether hydronephrosis but the tumor then continues to grow in the is indeed secondary to urinary tract obstruction perirenal urinoma. Resultant extensive defor- is more problematic. Also, the etiology of an mity makes tumor identification difficult. obstruction may not be evident with US. Gray-scale US is reasonable in monitoring Imaging residual postoperative urinary tract dilation in children. Normally infundibular and ureteral Most imaging of suspected obstruction is dilation decrease gradually after surgery. In straightforward. A contrast study of an acute children, US findings pointing to obstruction obstruction shows a persistent unilateral include a hyperechoic renal appearance, a nephrogram and delayed collecting system parenchymal rim of 5 mm or less, contralateral filling. It should be kept in mind that these hypertrophy, a resistive index (RI) of 1.10 or findings are not pathognomonic for urinary greater, an RI difference with diuresis of 70% or tract obstruction, and similar changes may be greater, a ureter diameter 10 mm or greater, and seen with vascular obstruction, a vasculitis, an aperistaltic ureter (91); how practical these infection, and a number of other causes of renal findings are in differentiating obstructive from failure, including acute glomerulonephritis and nonobstructive hydronephrosis is not clear. acute tubular necrosis. Resistance to renal arterial blood flow (RI), as Normally a pyelogram persists for a short measured with renal Doppler US, is increased in period of time after IV contrast. With obstruc- most acute obstructive uropathies. With unilat- tion, a pyelogram can persist for hours. A pyel- eral obstruction, RI and the pulsatility index ogram occasionally persists for weeks if the (PI) are greater in the obstructed kidney than a ureter is encased by tumor, and the lymphatics contralateral kidney, keeping in mind that RI are an obstruction. increases with age and some nephropathies. The Occasionally urinary tract obstruction published RI sensitivities in detecting an acute cannot be readily distinguished from non- urinary obstruction depend on accepted RI obstructive hydroureteronephrosis. In such a cutoff values, but even then they vary consider- setting the Whitaker perfusion test still has a ably, and some authors have concluded that RI role. This is an invasive test requiring per- values are not useful enough to detect acute cutaneous renal pelvis puncture, bladder urinary tract obstruction. catheterization, and measurement of pressure Occasionally endorectal or endovaginal 3D differences between the two sites during con- US is helpful with suspected distal ureteral or trast infusion. ureterovesical junction obstruction. Normal A prominent extrarenal pelvis detected with ureters have forceful ureteral jets. Initially after CT is differentiated from hydronephrosis by stenting, ureters have passive flow, with peri- evaluating the superior and inferior pole col- staltic activity only gradually becoming evident; lecting systems; calyces are not dilated in the Doppler US is not reliable in diagnosing an presence of a simple extrarenal pelvis. Com- obstruction in a stented ureter. puted tomography readily identifies a dilated A respiratory-triggered 3D fast spin-echo MR ureter, keeping in mind that on occasion a technique can detect urinary tract dilation 642

ADVANCED IMAGING OF THE ABDOMEN without the use of IV contrast. Comparing ureterovesical junction, followed by a site just breath-hold heavily T2-weighted sequences distal to the ureteropelvic junction and (thin-slice HASTE) with gadolinium-enhanced midureter at the iliac vessel level. 3D FLASH MR sequences in patients with acute One complication among patients with a flank pain, both MR urography techniques were chronically impacted ureteral stone is a stric- comparable in detecting obstruction (92); ture; a previous ureteral perforation at the however, 3D FLASH was superior for stone site of a stone appears to be a risk factor for detection, reaching a sensitivity of 96% to 100% stricture. and specificity of 100% compared with a sensi- Not all flank pain is due to renal colic.Among tivity of 54% to 58% and specificity of 100% for less common causes mimicking the flank pain HASTE T2-weighted sequences. For the best of renal colic are ovarian vein thrombophlebitis. results, both sequences are recommended in Acute renal artery obstruction can mimic renal patients with acute flank pain. colic pain. A unique cause of renal colic was a Perirenal fluid is common in acutely bird shot calculus after a gunshot wound to the obstructed kidneys but generally not present abdomen (94). with a chronic obstruction. The HASTE MR urography, which identifies not only ureteral Imaging obstruction but also presence of any perirenal fluid, detects a high perirenal signal in most Considerable literature analyzed the role of con- patients with acute ureteric obstruction and is ventional radiography and US in patients with thus useful in differentiating acute from chronic flank pain believed to be renal colic in origin, obstruction. with conventional teaching being that about Radionuclide renography also identifies most 80% of ureteral stones contain sufficient ureteral obstruction if renal function is ade- calcium to be radiopaque and thus could be quate, but does not provide anatomic detail. identified with conventional radiography. Some Either Tc-99m-DTPA or Tc-99m-MAG3 is com- studies reported a sensitivity and specificity of monly used. Radiotracer stasis is evident in a over 90% in detecting a calculus, especially if dilated system, be it obstructed or not. In the conventional radiography and US are com- absence of obstruction, vigorous hydration or bined. More critical studies, however, do not the use of a diuretic result in a washout, but achieve such optimistic results. In some studies an obstruction leads to prolonged retention. conventional radiographs could detect ureteral Comparing furosemide injected 20 minutes calculi with a sensitivity of <50%. A prospective after renography versus furosemide injected 15 study of patients with renal colic achieved US minutes before renography in children, the sensitivity of only 61% in detecting ureteral earlier furosemide injection revealed seven calculi, while CT sensitivity was 96% (95). Inci- times more obstructions than the later injection dentally, conventional abdominal radiography (93). and CT scout radiography have different reso- lution; thus abdominal radiography revealed 60% and CT scout radiography only 47% of Obstruction by Stones (Renal Colic) ureteral calculi (96). Digital abdominal radiog- Clinical raphy identifies most urinary tract calculi >5mm and those calculi having a CT attenua- Acute flank pain and hematuria are typical pre- tion of >300HU (97). Stone visualization can be sentations in patients with acute obstruction. enhanced on a CT scout view by a low kilovolt- About 85% of these patients have hematuria.An age setting. obstruction induces prostaglandin secretion, Traditionally, IV urography was performed which increases renal blood flow and glomeru- for suspected renal colic, but it has been sup- lar filtration rate and results in renal colic. Nev- planted to a large extent by noncontrast CT.That ertheless, a clinical diagnosis of obstruction is noncontrast CT is as effective as or better than not straightforward and is accurate in only IV urography in identifying ureteral calculi and about half of the patients. equally effective in determining the presence Although a stone can obstruct anywhere in or absence of ureteral obstruction has been the ureter, the most common site is at the confirmed by numerous studies. Helical CT also 643

KIDNEYS AND URETERS provides such accessory signs as periureteral A passed stone is occasionally detected in the and perirenal fat infiltration and ureteral bladder. Secondary signs of prior obstruction, edema, and, in fact, achieves greater detection of namely, a surrounding soft tissue rim without renal and ureteral calculi in patients with acute evidence of a ureteral stone, are often still flank pain than IV urography. Most helical CT evident. studies report sensitivities and specificities in A caveat is in order for the patient with clin- the high 90% for detecting obstructing ureteral ically suspected obstruction due to a renal stone calculi. Also, in the absence of urolithiasis an but a normal unenhanced CT study. Renal alternative diagnoses can often be established. ischemia secondary to renal artery obstruction As a result, in a number of countries, including is in the differential diagnosis and will not be the United States, noncontrast helical CT is pre- detected with precontrast CT. Also, a rare renal ferred; in other countries,such as France,US has carcinoma, not evident on precontrast CT, first a more prominent role. presents with flank pain (98), and thus postcon- One side effect of clinicians becoming more trast CT is necessary in these patients. Alterna- comfortable with unenhanced helical CT in a tively, Doppler US should detect major renal setting of suspected acute urinary tract obstruc- ischemia. tion is that the indications for this technique are Once a site of obstruction is identified, being arbitrarily expanded. As a result, the narrow collimation scanning of the region in number of stones being detected is decreasing question often identifies an etiology. Calculi and the number of other diagnoses is increas- as small as 1mm in diameter are detected. ing, a trend bound to continue. Given such Secondary signs of obstruction consist of hy- expanded indications, an argument can be droureter, perinephric and periureteral strand- made for adding a contrast-enhanced CT study ing, ureterovesical junction edema, hydro- if the initial unenhanced CT is negative for nephrosis, and renal enlargement; keep in obstruction by stones, yet little published data mind that calyces are not unduly dilated and supports such an approach. little perinephric stranding is evident early in Phleboliths are in the differential diagnosis of an obstruction or with an incomplete obstruc- pelvic calcifications. Most phleboliths are round tion. In general, the extent of perinephric and on conventional abdominal radiographs edema correlates with the degree of ureteral often have a radiolucent center, a finding obstruction. Although an indirect sign, attenua- identified with CT in about 10%. Their size and tion difference between kidneys greater than or appearance varies and no pathognomonic sign equal to 5.0 on unenhanced helical CT achieved differentiates ureteral stones from phleboliths a 60% sensitivity and 100% specificity in detect- aside from establishing ureteral continuity for a ing ureteral obstruction (99). stone. Especially difficult with noncontrast CT is Whether a stone is impacted at the distinguishing pelvic phleboliths from mini- ureterovesical junction or is already in the mally obstructing distal ureteral calculi,at times bladder can be difficult to determine for stones leading to unnecessary retrograde urography. located close to the ureterovesical junction. If Many ureteral stones are surrounded by a soft the diagnosis is uncertain with the patient tissue rim (soft tissue rim sign), representing imaged in the supine position, a prone position ureteral wall and possible edema, although an image will usually distinguish between these occasional phlebolith also has a soft tissue rim. entities. Surrounding edema is less evident in patients Color Doppler US in patients with complete with chronic renal failure. ureteral obstruction by a stone revealed the An eccentric, tapering soft tissue density absence of a normally present ureterovesical jet; pelvic vein adjacent to a calcification identifies with incomplete obstruction the jet tended to be a phlebolith (comet sign or tail sign); this continuous but decreased in volume and inten- appearance also is not pathognomonic and a sity. Also, a distal ureteral stone diverts the jet curvilinear nondilated ureter can mimic this orientation from its usual anteromedial direc- appearance. Prevalence of the comet sign tion. These findings are indirect evidence for a varies—some studies find it only in a minority ureteral stone. of phlebolith while others believe it is present in Contrast enhanced MRI can also suggest an a majority. obstructed ureter. Defining renal transit time as 644

ADVANCED IMAGING OF THE ABDOMEN the time interval between contrast appearance while some evolve into renal damage. If stable, in the kidney and in the ureter at or below the US is useful in following this condition every 6 lower pole level, a time >490sec suggests an months or so. obstructed ureter (100); a normal transit time is <245sec. Imaging Therapy Urography readily detects a ureteropelvic junc- tion obstruction. Some have suggested that US The degree of obstruction, the stone location, overdiagnoses this condition, although others and the underlying renal function are not major disagree and believe that US allows the detec- issues during initial therapy of patients with tion of an obstruction at an earlier age. acute ureteral stone obstruction. More relevant Computed tomography angiography of is whether CT can predict which stones will pass patients with symptomatic ureteropelvic junc- spontaneously. In patients with a single stone, tion obstruction should achieve near 100% the mean stone diameter in those with sponta- seusitivity and specificity in detecting crossing neous stone passage was 2.9mm and in those arteries. These vessels are either posterior or with failed conservative therapy 7.8mm (101); anterior to the ureter. Axial CT generally is also, perinephric fat stranding and perinephric sufficient, although 3D reconstruction provides fluid collections were significantly higher in better spatial orientation of the surrounding patients with spontaneous stone passage. structures. The usual options for obstruction and infec- Nonenhanced color Doppler US detected only tion due to ureteral calculi are percutaneous 65% of crossing vessels in patients with nephrostomy or retrograde ureteral catheteriza- ureteropelvic junction obstruction, while con- tion with drainage. Both procedures relieved an trast-enhanced Doppler US detected 96% (102). obstruction and infection; the choice depends Doppler US proponents thus maintain that their on procedure availability and cost. detection results are equivalent to those achieved by CT. Ureteropelvic Junction Obstruction Occasionally an infant with a ureteropelvic junction obstruction has such large renal pelves Clinical that they extend almost to the bladder. In such a setting US may suggest an incorrect diagnosis Ureteropelvic junction obstruction is more of ureterovesical junction obstruction.Likewise, common on the left side.Depending on chronic- occasionally vesicoureteral reflux mimics a ity, the resultant distention ranges from an ureteropelvic junction obstruction. almost-normal mild renal pelvis prominence to Patients with an unilateral ureteropelvic junc- severe hydronephrosis. Likewise, patients can be tion obstruction have increased differential asymptomatic or have a palpable mass, with the function as shown with DTPA scintigraphy, later more common in infants. possibly due to compensatory hyperfunction. Both intrinsic and extrinsic obstructions develop at the ureteropelvic junction. Intrinsic obstructions include congenital strictures, Therapy and Outcome ischemic strictures, fibrosis, redundant mucosa, ureteral kinks, or even a peristaltic abnor- Over half of neonates with unilateral hydro- mality. With some apparent strictures no nephrosis detected by pre- and postnatal US underlying abnormality is found. Extrinsic and followed with sequential nuclear renograms obstructions include fibrosis and compression eventually revert to normal renal function and by adjacent blood vessels; the latter are usually washout; those with poor or worsening kidney incidental findings, although an occasional function and drainage require pyeloplasty. crossing renal vessel leads to intermittent Adjacent arteries are a relative contraindica- ureteral obstruction. tion to endopyelotomy, and recognition of Most mild ureteropelvic junction obstruc- crossing vessels is of prognostic value for suc- tions remain stable for prolonged periods of cessful endopyelotomy. Nevertheless, the need time. An occasional one resolves spontaneously for preoperative imaging has been questioned 645

KIDNEYS AND URETERS and successful endopyelotomy has been per- Success depends not only on the underlying eti- formed in patients with ureteropelvic junction ology and the length of a stricture but also on obstruction who had CT evidence of crossing relative operator expertise. Balloon dilation vessels. using a percutaneous approach has become Children with unilateral ureteropelvic junc- popular, including dilation of restenosis, tion obstruction have not only impaired renal although overall the long results of percuta- function but also delayed body growth. Long- neous dilation have been poor and, at times, standing dilation often persists after pyelo- even multiple dilations do not achieve ureteral plasty, but renal function improves, mostly in patency. younger children. Improvement is slow—only A rare cause of bilateral ureteral obstruction in a minority during the first 6 months, but a and hydronephrosis is retroperitoneal systemic majority of the patients improve within 2 years. sclerosis. Long-term follow-up of retrograde balloon dilatation of ureteropelvic junction stenosis reveals variable results; some patients had per- Extrinsic sistent residual stenosis, but in a few the pro- cedure led to complete ureteropelvic junction Ureteral metastases have already been dis- obstruction requiring surgical correction. cussed. Occasionally inflammation surrounding an abdominal aortic aneurysm entraps one or both ureters and results in obstruction. Simi- Ureteral Obstruction larly, extrinsic ureteral compression and Strictures obstruction occurs with abdominal fibromato- sis due to several disorders. The etiologies of a benign ureteral stricture are Aberrant arteries may compress a ureter, listed in Table 10.8. Ureteral ischemia is a not leading to varying degrees of obstruction. As uncommon cause of ureteral stricture. Most already mentioned, the most common location benign strictures involve a short segment, is at the ureteropelvic junction, but it can occur although an occasional one extends for consid- anywhere along the ureter. erable length. Ureteral obstruction develops secondary to Benign ureteral strictures are dilated using an adjacent neoplasm, perforated appendiceal either an antegrade or retrograde approach. abscess, and an adjacent hematoma. An ileoce- cal phlegmon in Crohn’s disease not uncom- monly obstructs the right ureter, but rarely the left. Extensive periureteral venous collaterals due to a thrombosed or absent infrarenal vena cava can result in ureteral obstruction. Anecdo- Table 10.8. Etiologies of benign ureteral strictures (from more tal reports describe an infected urachal cyst, common to less common) uterine prolapse, and even methacrylate migrat- Ureteral stones ing into the pelvic cavity after hip arthroplasty, Ischemia resulting in ureteral obstruction. Castleman’s Thromboemboli disease can present as a recurrent tumor, Vascular reconstructive surgery detected by imaging (103). Sequelae to adjacent organ resection Placement of metallic stents in ureters Polyarteritis nodosa obstructed by an extrinsic tumor, such as an Trauma extensive gynecologic cancer, is effective in maintaining renal function during chemother- Adjacent Crohn’s disease apy or radiation therapy. If necessary, these Infection stents can be augmented by cystoscopically Tuberculosis inserted temporary J endostents. Renal RI, Bilharziasis obtained from Doppler US data, was found Retroperitoneal fibrosis useful in following patients with unilateral extrinsic ureteral obstruction after therapy with Idiopathic double-J ureteral stents (104). 646

ADVANCED IMAGING OF THE ABDOMEN

Retrocaval Ureter Antegrade ureteral intussusception can develop after antegrade instrumentation. A retrocaval ureter represents an anomalous Intussusception can be related to an indwelling vena caval development with persistence of the endoprosthesis. ventral vasculature. A retroiliac ureter is rare. A cholesteatoma in the midportion of the left The clinical significance of a retrocaval ureter ureter led to obstruction and hydronephrosis depends on the degree of obstruction. Urogra- (105). phy suggests the diagnosis. Contrast-enhanced Rarely,polyarteritis nodosa is associated with CT should be diagnostic. ureteral obstructions, presumably due to a peri- Reanastomosis using a laparoscopic ap- ureteral vessel vasculitis. proach is a viable option. During Pregnancy Ovarian Vein Syndrome Proximal ureters dilate during pregnancy due Ovarian vein syndrome consists of ureter com- to extrinsic compression, although hormonal pression between the external iliac artery and a factors may also play a role. At times dilation is dilated ovarian vein. It is more common on the asymmetrical and a superimposed ureteral cal- right. Occasionally a thrombosed right ovarian culus is suspected. Dilation gradually resolves vein produces a distinct impression on the after delivery. ureter, although obstruction is rare. With suspected obstruction during preg- A similar syndrome on the left side is due to nancy US evaluates hydronephrosis and at times ureter compression between a dilated ovarian suggests an etiology. Ureteral jets identified at vein and the psoas muscle. color Doppler US imply lack of obstruction at the ureterovesicular junction. Occasionally late Endometriosis in a pregnancy no ureteral jet is identified in the absence of obstruction; turning the patient to Ureteral endometriosis is generally part of a contralateral decubitus position generally diffuse pelvic involvement. Both focal and restores this sign. diffuse disease lead to ureteral obstruction, gen- Spontaneous urinary tract rupture during erally in the distal ureter. It can be silent and pregnancy is rare and generally occurs in a progress to loss of renal function. At times both setting of a diseased kidney. Rupture is either in ureters are involved. the collecting systems or it involves the kidney A typical appearance is that of a focal or long parenchyma. Most ruptures occur in the second infiltrating-appearing ureteral stricture, similar or third trimester. to encasement by extrinsic fibrosis or tumor. If relief of an obstruction is believed neces- Retroperitoneal fibrosis has a similar appear- sary, a percutaneous nephrostomy rather ance but the two conditions have different clin- than surgical decompression should be con- ical presentations. sidered. Many women with symptomatic acute hydronephrosis are managed with ureteral Hernia stenting. Ureteral herniation is a rare cause of ureteral obstruction. Possible herniation sites include Diabetes Insipidus inguinal, femoral, and sciatic hernias.A number Nephrogenic diabetes insipidus is a cause of of these obstructions are chronic, manifesting nonobstructive urinary tract dilatation. by more proximal hydronephrosis. Any imaging modality visualizing the ureter should detect such a hernia. Reflux

Other Obstructions Clinical Ureteral polyps are not common. Occasionally Vesicoureteral reflux is abnormal. A number of such a polyp intussuscepts and results in an investigators ascribe most reflux to an abnormal acute obstruction. ureterovesical junction, although morphologi- 647

KIDNEYS AND URETERS cally this junction is indistinguishable from often called screening, in a pure sense this is no those without reflux. Nerve density and distri- longer screening but an attempt to detect reflux bution are similar. Especially in male infants, in a symptomatic patient. Young boys probably vesicoureteral reflux tends to be associated with should also be studied if they develop an infec- abnormal voiding urodynamics, such as a small tion because of the relatively high prevalence of voided volume, inadequate voiding dynamics, posterior urethral valves. Screening of girls with markedly dyssynergy, and an obstructive pat- a first infection is somewhat controversial, but a tern. In males an association exists between general trend toward earlier study is evolving. reflux and a simultaneous increase in detrusor In women a search for reflux is appropriate for pressure. A familial tendency to vesicoureteral recurrent infection. reflux exists. The two primary examinations used to detect In children, vesicoureteral reflux is associated vesicoureteral reflux are fluoroscopic voiding with urinary tract infection and impaired cystourethrography and radionuclide cystogra- growth, although whether reflux per se or the phy, with some centers also having introduced often commonly associated renal tubular acido- contrast enhanced voiding urosonography. sis is responsible for growth failure is not clear. Each study has its proponents. Scintigraphy Although both reflux frequency and grade tend has a lower radiation dose but also provides to decrease with age, reflux remains a common fewer anatomic details. One approach is to cause of end-stage renal failure requiring renal use voiding cystourethrography in boys, who transplantation. Some of these children also are more prone to have other underlying develop hypertension or urinary infections and anatomic abnormalities such as urethral valves, thus may also require bilateral nephrectomies of and radionuclide cystography is girls, in whom the native kidneys. anatomic abnormalities are uncommon. Reflux tends to be intermittent, and the time Because of its low radiation dose, radionuclide to resolution varies widely. cystography is useful as a follow-up examina- A ureter inserting into a diverticulum is at an tion, but the lack of anatomic detail limits it as increased risk of vesicoureteral reflux. Patients a first study. with renal dysplasia are also at an increased risk A number of vesicoureteral reflux grading for reflux, although whether dysplasia is systems have been proposed. One classification, secondary to reflux is not clear. based on the results of voiding cystourethrog- raphy, is outlined in Table 10.9. Reflux can be Screening missed with incomplete bladder distention. At times reflux is observed only after several In view of renal parenchymal damage associ- episodes of bladder filling to capacity and ated with vesicoureteral reflux, should US having the patient void. If reflux is detected screening for reflux be instituted early in life? during a voiding cystourethrogram, the study Several studies have found that even using a should be modified so the degree of calyceal and meticulous technique, prenatal and neonatal ureteral dilation can be evaluated and any US achieves a low sensitivity for detecting vesicoureteral reflux. In children, often major renal damage has already occurred when an Table 10.9. Classification of vesicoureteral reflux acute urinary tract infection or a megaureter Grade Description becomes evident. One proposal is to perform I Reflux into ureter cystography in those at risk for reflux, such as II Reflux into collecting system, without dilation newborns with pyelocaliceal dilation and in sib- and with normal calyceal fornices lings of those treated for vesicoureteral reflux, III Reflux into collecting system, with mild to yet such an approach also misses some infants moderate ureter dilation and mild dilation with reflux. of renal pelvis IV Moderate ureter and renal pelvis dilation, obliteration of forniceal angle but papillary Detection outline is preserved A search for reflux appears appropriate in V Severe ureter, renal pelvis and caliceal dilation, papillary outline not preserved infants with a urinary tract infection. Although 648

ADVANCED IMAGING OF THE ABDOMEN underlying obstruction detected. Often a dupli- becomes apparent during a second cycle of cated collecting system can be suspected from bladder filling. When to perform such a second this examination. cycle is not clear; a positive study is more What is the role of US in detecting reflux? common in patients strongly suspected of Intermittent renal collecting system dilation having reflux. and contraction during real-time renal US is an The SPECT Tc-99m-DMSA is a noninvasive indirect sign of vesicoureteral reflux (106). Like- test useful in assessing functional kidney wise, renal pelvis dilation during bladder con- impairment in children due to pyelonephritis or tractions points to reflux, yet a large minority of in those with vesicoureteral reflux. children with negative renal US have reflux at voiding cystourethrography. Therapy In spite of some rather optimistic claims, it is still difficult to gauge the accuracy of intravesi- Due to increased pre- and postnatal US screen- cal contrast enhanced voiding US in detecting ing, more infants with vesicoureteral reflux are and grading vesicoureteral reflux in children. being detected. Reflux is being managed both Although presence of microbubbles in the medically and surgically. Endoscopic therapy ureters or renal pelves does signify reflux, in consists of injecting polytetrafluoroethylene one study 38% of such reflux was graded (Teflon) or polydimethylsiloxane (Macroplas- either lower or higher than with voiding cys- tique). Resection after the failure of endoscopic tourethrography (107). Additional work is nec- therapy reveals that both substances induce an essary to place contrast enhanced voiding US in inflammatory giant cell macrophage reaction, a proper clinical perspective. new vessel formation, and fibrosis (108). An occasional author suggests air as a US Among 302 children under 11 years of age bladder contrast agent; although uncommon, with urinary tract infection and grade III or IV intravasation of an instilled contrast agent does vesicoureteral reflux enrolled in the European occur, especially with the distention pressures branch of the International Reflux Study in generally employed to detect reflux, and air thus Children group and randomly assigned to sur- cannot be recommended. gical or medical therapy, follow-up for 10 years Mild renal pelvic dilation detected at renal US with serial IV urography revealed no significant is not a reliable sign of vesicoureteral reflux. An difference in mean renal growth between the increase in renal pelvic size on postvoid US also two groups (109). Debate continues, however, does not signify vesicoureteral reflux. about the relative merits of conservative versus Upper urinary tract wall thickening in surgical therapy. children occurs secondarily to urinary tract infection, chronic obstruction, and chronic vesi- Conventional Surgery coureteral reflux.Thus voiding cystourethrogra- phy appears reasonable to evaluate for reflux in The classic surgical therapy for vesicoureteral these children if US detects upper urinary tract reflux is ureteral reimplantation. Infants with wall thickening. reflux typically undergo surgical correction at Radionuclide cystography is performed with about the age of 6 months, although in a setting Tc-99m–sulfur colloid (it is not absorbed from of hydronephrosis or renal damage correction the bladder). Reflux is detected as any activity as early as 1 month of age is performed. In some superior to the bladder. A reflux grading system surgical centers a very high success rate in cor- of mild, moderate and severe is generally recting reflux is achieved. employed. This radionuclide test provides A minority of patients with unilateral vesi- grossly similar information to a voiding cys- coureteral reflux treated by reimplantation tourethrogram regarding reflux, although con- develop postoperative contralateral vesi- tinuous monitoring during scintigraphy may coureteral reflux; most such reflux resolved better detect intermittent reflux. Its disadvan- spontaneously.Although it is tempting to attrib- tage is a poorer spatial resolution.At times vesi- ute any new contralateral reflux to the surgical coureteral reflux is not evident during an initial procedure, one should keep in mind that new fluoroscopic or scintigraphic study, but reflux reflux develops in some children. 649

KIDNEYS AND URETERS

In some children with persistent vesi- with an adjacent calyx; thus postcontrast they coureteral reflux after ureteral reimplantation, opacify only after contrast enters the involved subsequent endoscopic subureteral Teflon injec- calyx, differentiating them from papillary tion corrects the reflux in most. necrosis,which,being in continuity with tubules of Bellini, opacifies before the involved calyx. Injection Therapy Some contain debris or stones. Delayed contrast filling is evident with some. Subureteral collagen or polytetrafluoroethylene A cyst communicating with a calyx is a non- (Teflon) injection is an alternative therapy to specific finding: a pyelogenic cyst or any surgical ureteral reimplantation and it corrects inflammatory or neoplastic tumor can rupture reflux in about 80% of patients. In children with into a calyx. Radiographically, an abscess that neurogenic bladder dysfunction and vesi- has drained into an adjacent calyx has a similar coureteral reflux, success rates are greater after appearance. ureteroneocystostomy than after subureteral Percutaneous calyceal diverticulectomy Teflon injection, yet the latter procedure is often (most with stones) consists of stone removal employed in managing reflux because of relative and diverticular neck incision or dilation and procedure simplicity and ability, if necessary, to diverticular wall fulguration. perform secondary reimplantation. The opera- tive cost is considerably less than that for reim- Ureteral plantation, and morbidity is minimal. Results of endoscopic collagen injection in The pathogenesis of ureteral diverticula is not treating children with reflux into a totally dupli- clear. Some authors refer to them as pseudodi- cated ureter system were disappointing; eventu- verticula. They are usually detected during ally many of these children require surgical high-quality urography or retrograde pyelogra- correction. phy and appear as small ureteral outpouchings. Among infants and children with posterior They occur primarily in the upper one third of urethral valves and vesicoureteral reflux, reflux the ureter and generally are multiple and often resolves in only a minority. Most require bilateral. correction. Associated urinary tract abnormalities Ultrasonography shows collagen to be hyper- are common, ranging from bladder outlet echoic compared to the bladder wall shortly obstruction, to neoplasms, to renal stones and after endoscopic subureteral injection, and it others. gradually becomes isoechoic. On a long-term basis US does not detect some residual peri- ureteral Teflon. Calcifications Urolithiasis Diverticula Clinical Calyceal Urolithiasis means a calculus within the urinary tract. Renal (nephrolithiasis) and ureteral Calyceal diverticula are lined by transitional calculi predominate in developed countries, epithelium and communicate with an adjacent while bladder calcifications are more common calyx. They can be located anywhere in the in underdeveloped parts of the world. Stones collecting system, although upper and lower range from small to large. Most radiologists pole fornices predominate. Their pathogenesis have encountered a giant staghorn calculus; is unknown. Most are incidental findings. An these have a complex composition. An underly- occasional one becomes obstructed or is a site ing urinary tract infection is common. for stone formation and a nidus for infection. Most patients with nonobstructing stones are Many of these diverticula have a typical asymptomatic, although an occasional stone radiographic appearance. They communicate results in hematuria or infection. 650

ADVANCED IMAGING OF THE ABDOMEN

In general, about one third of patients with a Patients with gout, Crohn’s disease involving first renal stone develop a recurrence within 5 the small bowel, and some myeloproliferative years. These patients are usually investigated for disorders have an increased prevalence of uric an underlying cause, such as primary hyper- acid stones. Pure uric acid stones are lucent. parathyroidism, renal tubular acidosis, urinary Cystine stones develop in a setting of tract infection, and cystinuria. Urography, lately cystinuria, a rare autosomal-recessive disorder. supplanted by noncontrast CT, is often included These stones form in the first and second in the workup. Stone analysis often guides decades of life, while uric acid stones form in further studies. older patients. Cystine stones are only slightly A study based on data from the Swedish Inpa- radiopaque and range from small to large. tient Register and Swedish Cancer Registry fol- Recurrent stones are common, and lifetime lowed over 61,000 patients hospitalized for renal surveillance is necessary in affected individuals. or ureter stones and concluded that although Patients with struvite stones are prone to per- these patients are not at risk for developing a sistent infections. future renal cell cancer, they are at increased risk for renal pelvis, ureter, and bladder cancer Imaging (110); chronic irritation and infection appear to play a role because tumors tended to develop on Imaging of suspected urinary obstruction is the same side as stones. discussed in the previous Dilated Urinary Tract section. Associated Conditions Unenhanced CT readily identifies ureteral stones; keep in mind that with the use of wide Epidemiologic studies have established an asso- collimation some smaller stones, especially uric ciation between arterial hypertension and renal acid stones, are insufficiently dense to be stone disease. Alterations in calcium metabo- detected. Narrow collimation is thus necessary. lism play a role in both entities. At 1-mm collimation, stones can be grouped by Over 5% of cystic fibrosis patients older than attenuation: uric acid (least dense), cystine and 15 years have had urolithiasis in the past. struvite, calcium oxalate monohydrate, and Renal stone disease is induced by some drugs. brushite and hydroxyapatite (most dense) (112). In France, the most common drugs involved In vitro CT using HU measurements of chemi- are calcium and vitamin D supplements and cally pure stones identified the chemical com- long-term therapy with carbonic anhydrase position of uric acid, struvite, and calcium inhibitors (111). Furosemide therapy of prema- oxalate stones, but could not differentiate ture neonates for hyaline membrane disease is calcium oxalate from brushite stones and associated with urolithiasis. struvite from cystine stones (113); the use of Occasionally reported is heterotopic ossifi- dual CT kilovoltage aids differentiation. cation within a renal stone. A suture retained in The sonographic appearance of a calculus the renal pelvis from prior surgery can act as a reflects its size rather than its internal composi- nidus for subsequent calcification. tion. Calculi are hyperechoic and, aside from Patients with primary hyperparathyroidism small ones, have posterior acoustic shadowing have an increased prevalence of renal stones,but (Fig. 10.31). Ultrasonography is insensitive in only a small percentage of patients with idio- measuring stone size. Ultrasonography is better pathic stones are hyperparathyroid.A metabolic in detecting renal calculi than ureteral calculi. defect is detected in about half of patients who In women, transvaginal US can detect stones in develop calcium stones. the distal ureter, and this modality should be Calcium containing stones consist of calcium considered in the pregnant patient. oxalate and calcium phosphate. Less common An interesting stone finding consists of a are magnesium ammonium phosphate (stru- “twinkling”artifact detected by color and power vite) stones. Calcium oxalate stones are associ- Doppler US (114); this phenomenon appears as ated with certain blood groups. The prevalence a rapidly changing color complex located of these stones in patients with blood group O behind a stone, similar to a comet’s tail. It aids is several times greater than in patients with in stone detection. Also, a twinkling artifact blood group A. depends, in part, on stone composition. Thus it 651

KIDNEYS AND URETERS

Extracorporeal Shock-Wave Lithotripsy

Extracorporeal shock-wave lithotripsy (ESWL) is now the treatment of choice for most larger renal or ureteral calculi. Both US and fluoro- scopic guidance are employed. Occasionally IV contrast is necessary to define a stone. Large stones are often approached by both ESWL and percutaneous nephrolithotomy, while patients with an underlying congenital anomaly tend to undergo surgical reconstruction and stone clearance. Extracorporeal shock-wave lithotripsy is used to treat patients with urolithiasis in a Figure 10.31. Right renal nephrocalcinosis in a child. Longitu- solitary kidney and patients with calculi in dinal US scan identifies numerous discrete hyperechoic foci in anomalous kidneys. An increased risk exists the kidney. (Courtesy of Luann Teschmacher, M.D., University of with a solitary kidney, because a subcapsular Rochester.) hematoma after ESWL in a solitary kidney can result in acute renal failure. Extracorporeal shock-wave lithotripsy is performed in chil- dren; although the procedure is similar to that is present with calcium oxalate dihydrate and in adults, some issues, such as sedation, are calcium phosphate stones, but it is absent with more pertinent to children. calcium oxalate monohydrate and urate stones The overall success rate for lithotripsy is (115). about 80%,although the rate varies among insti- Magnetic resonance reveals a stone as a signal tutions and with stone size and composition.An void, regardless of stone composition. T2- ESWL study found that 95% of calculi <15mm weighted MRI (MR urography) identifies hyper- in maximum length were successfully disinte- intense urine, at times in a dilated ureter, and a grated, while only 8% of those >25mm in length hypointense or signal void stone at the site of were disintegrated (117); for calculi between obstruction. A blood clot also results in a 15 and 25mm, however, instead of maximum hypointense signal. length, volume was a better indicator, with 90% Conventional radiographs are often of calculi <6cm3 successfully disintegrated, employed in follow-up of known stones; stones while none >6cm3 were disintegrated. Spicu- detected only with helical CT should be followed lated, low-density stones are cleared more with that imaging modality. Helical CT allows readily than smooth, dense stones. Peak shock 3D reconstruction of stone shape, number, wave pressure generated by many ESWL units at and size. The role of helical CT in lithotripsy the focus is between 80 and 120MPa, and, in planning is still evolving. theory, the peak pressure required to disinte- grate a 6-cm3 calculus was calculated to be Therapy approximately 80MPa (117). Technetium-99m-DMSA scintigraphy per- The ideal goal of therapy is to eliminate all frag- formed the day before and at least 6 months ments. One proposed stone management strat- after ESWL in children did not identify any egy consists of surveillance for asymptomatic significant parenchymal lesions (118); stone caliceal stones <5mm in diameter; symptomatic fragmentation or elimination was achieved in stones <20mm in diameter are treated with 90% of these children. Likewise, no blood pres- ESWL, while a combination of percutaneous sure or renal function changes were evident. nephrolithotomy and ESWL is used for stones In patients who become stone free after >20mm in diameter (116); stones resistant to ESWL, the ipsilateral typical recurrence-free ESWL, such as cystine stones, often require rates are about 95% and 65% after 1 and 5 years, percutaneous nephrolithotomy or ureteroreno- respectively, and vary depending on the therapy scopic endocorporeal lithotripsy. for any underlying lithogenesis. 652

ADVANCED IMAGING OF THE ABDOMEN

Morbid obesity makes ESWL difficult. thermal chemical decomposition rather than Patients with a bleeding diathesis require to photomechanical or photoacoustical frag- adequate perilithotripsy therapy. The literature mentation (119); thus calcium carbonate was suggests that lithotripsy is feasible in patients found in samples composed of calcium oxalate with calcified aneurysms and cardiac pace- calculi, calcium pyrophosphate in calcium makers, but it requires close monitoring. Preg- hydrogen phosphate stones, free sulfur, and cys- nancy is generally considered a contrain- teine in cystine stones and cyanide in uric acid dication to ESWL. calculi. Patients with a pheochromocytoma have had severe reactions while undergoing ESWL. Percutaneous Nephrolithotomy Less than 1% of patients develop a hematoma; preexisting hypertension is a risk factor for In a retrospective study of lower pole stones 10 perinephric or subcapsular hematoma. These to 20mm in size, a stone-free status was hematomas can be diagnosed by US and most achieved in 44% of patients with ESWL and 72% are managed conservatively. An occasional with percutaneous nephrolithotomy (120); the patient with a perirenal hematoma manifests difference in success rate was less significant for hypertension, generally transient; a rare patient smaller stones. On the other hand, morbidity develops permanent hypertension as a late was higher with the nephrolithotomy technique. finding; a temporal relationship to previous Severe hemorrhage developed in 2% of lithotripsy is difficult to establish; some of these patients after percutaneous nephrolithotomy patients have had decreased renal function (121); renal arteriography revealed a mix of prior to lithotripsy. arteriovenous fistulas, false aneurysms, and Fever suggesting postprocedure obstruction arteriolar injuries, all successfully treated by is approached with urinary tract drainage and embolization. possible ureteroscopy. Drainage catheters are inserted to bypass a heavy stone load. Few Staghorn Calculi complications are associated with these ureteral catheters, although encrustation becomes a Staghorn calculi are usually treated by either problem in catheters retained longer than about ESWL or surgery, but the optimal therapy is still 6 weeks. controversial. Lithotripsy alone is effective in A resultant fibrous scar, detected by imaging, about 50% of the patients. is presumptive evidence for renal parenchymal Ultrasonography guidance is an option for damage during lithotripsy. Posttherapy Tc-99m- percutaneous lithotomy, but the entire stone DMSA scintigraphy should detect any acquired burden is removed only in a minority of parenchymal scars after ESWL. Anecdotal com- patients; others require either lithotripsy or plications include renal laceration, small bowel surgery. perforation, splenic rupture, and even abdomi- Fiberoptic transurethral nephrolithotripsy nal aortic rupture. has been combined with ESWL to treat staghorn calculi. The stones are initially disintegrated by Ureteroscopy nephrolithotripsy, and ESWL is then performed for residual fragments. Using an ureteroscopic approach, therapy options for ureteral stones include laser or elec- Nephrocalcinosis trohydraulic lithotripsy or simply the use of endoscopic baskets and similar grasping tools. Nephrocalcinosis designates renal parenchymal Even intrarenal calculi are amenable to such calcifications. These calcifications range from therapy. discrete to diffuse and tend to be bilateral. Ureteroscopy is more successful than ESWL Nephrocalcinosis can be further subdivided by for larger calculi. One option is ureteroscopic location—cortex or medulla. In either site laser lithotripsy. Lithotripsy stone fragmenta- calcifications can be dystrophic or metastatic. tion is more successful in lower ureteral stones Dystrophic calcifications (those in abnormal than in upper ureteral stones. Stone fragmenta- tissue) develop at sites of ischemic, necrotic, or tion by holmium:yttrium-aluminum-garnet infected tissue, while metastatic nephrocalci- (Ho:YAG) lithotripsy is primarily due to photo- nosis develop in normal tissue. 653

KIDNEYS AND URETERS

Medullary nephrocalcinosis tends to be bilat- A spontaneous nephrocutaneous or neph- eral and symmetrical. It has developed in a roenteric fistula is rare and is usually associated setting of vesicoureteral reflux, presumably with a staghorn calculus and obstruction. A related to urine stasis in collecting tubules. fistula can be secondary to an extrinsic infection Precontrast CT in medullary nephrocalci- or, less likely, a neoplasm. nosis reveals multiple medullary calcifications. Computed tomography shows gas-fluid Some mimic nephrolithiasis. collections within the kidney, perinephric Ultrasonography appears to be reliable in inflammatory changes, and, at times, extension grading nephrocalcinosis, although reliability of renal contrast outside the collecting system. in assessing change between examinations Neither an antegrade nor a retrograde pyelo- is only fair. Ultrasonography in primarily gram may define a renal fistula. medullary nephrocalcinosis reveals hypere- Antegrade stent insertion is the primary choic medullary pyramids. Posterior shadowing therapy of choice for an enteroureteral fistula. develops only when the condition is advanced. If the antegrade approach fails, a cystoscopic Ultrasonography findings may precede the retrograde approach will generally also fail. development of visible calcifications seen with In some patients combining an antegrade conventional radiography. with a retrograde approach succeeds in stent placement. Sarcoidosis Sarcoidosis typically involves lungs, skin, and, at times,eyes.In a setting of sarcoidosis about 25% Renal Failure/Insufficiency of patients develop hypercalciuria and 15% urinary lithiasis. A rare manifestation of renal Clinical sarcoidosis is focal granulomatous interstitial nephritis (122), with secondary ectopic cal- Differentiation of renal failure from renal citriol secretion by the granulomas and result- insufficiency depends on the degree of loss in ant nephrocalcinosis. renal function, with the final end point of renal Rarery, ureteral infiltration by sarcoidosis failure being end-stage renal disease. The eti- leads to obstruction and hydronephrosis. ologies of renal failure are complex, varied, and often interrelated; some are listed in Table 10.10. Calcifications in Cysts Differentiation into acute and chronic renal failure aids in clinical management. A subdivi- An occasional benign cyst contains thin, sion into prerenal, renal, and postrenal etiolo- curvilinear calcifications, probably induced by gies is helpful. Diabetes mellitus is the most prior hemorrhage or infection. Any amorphous common cause of chronic renal failure in adults. calcifications should raise suspicion for a Vesicoureteral reflux is probably the common- neoplasm. est cause of end-stage renal failure in children. Most patients with glomerular kidney disorders Hyperoxaluria have a progressive loss of renal function, with eventual histologic evidence of glomeruloscle- One of the conditions resulting in diffuse corti- rosis and tubulointerstitial fibrosis. Presumably cal calcifications is oxalosis. When extensive, such fibrosis is not the initiating factor in renal these calcifications can be identified with con- failure but represents a final pathway. ventional radiography. Urinary tract obstruction is an uncommon cause of renal failure, except in individuals with a single kidney, where it can lead to either Gas in the Parenchyma or acute or chronic renal failure. Ultrasonography readily detects hydronephrosis and can steer the Collecting System further workup, but keep in mind that an occa- sional obstructed urinary system does not lead Gas in the renal parenchyma or collecting to hydronephrosis. Intravenous urography is system can be secondary to a fistula, abscess, not indicated in acute renal failure even with a or emphysematous pyelonephritis. suspected urinary obstruction. 654

ADVANCED IMAGING OF THE ABDOMEN

Table 10.10. Conditions associated with renal failure Vascular causes (hypoperfusion) Rhabdomyolysis Bilateral renal artery occlusion/stenosis Pregnancy-related Shock Hypertensive nephropathy Nephrotic syndrome Other causes for ischemia Membranous nephropathy Diabetic nephropathy Glomerulonephritis (acute or chronic) Vesicoureteral reflux Hemolytic-uremic syndrome Urinary obstruction Cirrhosis/hepatorenal syndrome Stones Benign strictures Congenital medullary cystic disease Malignant obstruction Polycystic kidney disease Urinary infection Autosomal dominant Autosomal recessive Papillary or cortical necrosis Alport’s syndrome Acute tubular necrosis Chronic tubular dysfunction Acute interstitial nephritis Renal tubular acidosis Drug or poison induced Fanconi’s syndrome Cystinosis Tubulointerstitial nephritis Multiple myeloma

Upper gastrointestinal symptoms are com- called the kidney sweat sign, in 14% of 330 mon in patients with chronic renal failure. Most patients with renal failure (123); this finding patients with chronic renal failure have an occurs bilateral. Magnetic resonance imaging abnormal radionuclide solid meal gastric emp- reveals a loss of corticomedullary interface in a tying time. Renal failure patients developing setting of renal insufficiency due to a variety of upper gastrointestinal bleeding should be sus- conditions. The primary role of imaging is to pected of erosive gastritis, erosive esophagitis, exclude obstruction and detect hydronephrosis, and gastric ulcer. calculi, and location and size of the kidneys. An occasional patient with renal failure Depending on the information needed, US or develops spontaneous hypoglycemia. scintigraphy is sufficient in some patients, while The following discussion of renal failure in others noncontrast CT is necessary. In some causes is subdivided only approximately and patients with renal failure a contrast study is overlap exists. For instance, hypoperfusion necessary to exclude a vascular etiology. (shock) due to trauma is a cause of acute prer- Magnetic resonance imaging measurement enal failure but can also lead to acute tubular of mean cortical thickness in patients with necrosis. glomerular disease differs significantly from that in patients with normal kidneys and those Imaging with other renal parenchymal disorders. The normal postcontrast pyelocaliceal phase MR Renal failure often has no characteristic signal intensity decrease is lacking in renal imaging characteristics per se, but certain insufficiency patients; this change is due to the findings are useful. The kidneys tend to reduced renal concentrating ability in these increase in size in patients with acute renal patients. Also, a minority of patients with renal failure, an increase measurable with US. Chro- disease have diffuse medullary hyperintensity nic renal failure, on the other hand, results in on delayed postcontrast images. small, hyperechoic kidneys due to underlying Serum creatinine level is only a crude esti- sclerosis and fibrosis. Ultrasonography mate of renal function; creatinine clearance is a identified an extracapsular hypoechoic rim, better test, although it is of limited use in a 655

KIDNEYS AND URETERS setting of acute renal failure. Newer methods of 1. Iodinated radiographic contrast agents. estimating glomerular filtration rate include The risk of nephrotoxicity is increased in a plasma clearance of small amounts of iohexol, a setting of impaired renal function. nonionic contrast agent. A correlation exists 2. Viper venom is mainly hemotoxic and between renal clearance of inulin and iohexol causes coagulation abnormalities, but in patients with moderate to severe renal about one third of patients after systemic failure. Doppler US appears useful in following envenomation have renal involvement; acute renal failure; recovery of renal function is renal biopsy in those with severe renal dys- associated with a progressive drop in resistive function reveals acute tubular necrosis. index. 3. Overexposure to aliphatic hydrocarbons The normal postintravenous contrast pyelo- present in diesel fuels and solvents. caliceal phase MR signal intensity decrease is 4. A nephropathy due to Amanita phalloides lacking in renal insufficiency patients; this exposure. change is due to the reduced renal concentrat- ing ability in these patients. Clinically, acute tubular necrosis is mimicked by bilateral renal artery occlusion or severe Vascular Causes stenosis, and these conditions should be excluded. Ultrasonography identifies normal A common cause of acute prerenal failure is kidneys in a setting of acute tubular necrosis. hypoperfusion due to either cardiac failure or Doppler US, however, reveals an increased RI in hypovolemia; the latter condition is detected most of these patients. Scintigraphy with Tc- with a fluid-load challenge.Bilateral renal artery 99m-DTPA or Tc-99m-MAG3 is useful in these or vein occlusion, although rare, also leads to patients to confirm the presence of acute renal hypoperfusion, with a lack of response to tubular necrosis and exclude renal vascular a fluid load. Vascular occlusion in a solitary occlusion; parenchymal activity without excre- kidney is perhaps a more common cause of tion suggests acute tubular necrosis. acute failure than bilateral vascular involve- Intravenous contrast in patients with acute ment; US should exclude this finding. tubular necrosis shows a dense, persisting Atherosclerotic vascular disease or small nephrogram with little or no excretion of vessel disease such as cholesterol crystal contrast from enlarged kidneys. Contrast can embolization have led to acute renal failure. persist in renal parenchyma for a prolonged Drug-induced vasomotor disorders also play a time. role. Bilateral vasculitis leading to renal artery obstruction and small vessel disease are less common causes of acute renal failure. Acute Cortical Necrosis Hypertensive nephropathy and related renal artery stenosis are common causes of chronic The etiology of acute cortical necrosis is usually renal failure. The latter is discussed in Chapter multifactorial. Prior to 1980, obstetrical causes 17. were common; since then sepsis, dehydration, drugs (discussed in the next section), and, in Acute Tubular Necrosis India, snake bite predominate. Shock and trans- fusion reaction have been implicated. Urinary Acute tubular necrosis is a common cause obstruction is occasionally implicated. Chronic of acute renal failure and associated high pyelonephritis, diabetes, and hypotension prob- morbidity and mortality. The causes of acute ably also play a role in this condition. tubular necrosis include nephrotoxic, ischemic, The underlying abnormality is cortical hypotensive, and other factors. It occurs after ischemia with relative sparing of medulla. bilateral ureteral obstruction due to any cause. Peripheral cortical regions remain viable due The evidence suggests that it is induced by to intact capsular vessels. Initially involved tubular damage and tubular obstruction, kidneys enlarge but on a chronic basis shrink in although a role for renin is also suggested. size. Included among nephrotoxic agents are the Acute cortical necrosis can be unilateral or following: bilateral. The papillae cavitate, and communi- 656

ADVANCED IMAGING OF THE ABDOMEN cate with an adjacent calyx, and the sloughing of Acute Interstitial Nephritis papillae leads to calyceal clubbing. In time, linear cortical calcifications develop. Acute interstitial nephritis is believed to repre- A diagnosis of acute cortical necrosis is most sent an acute hypersensitivity reaction, most often suggested by IV urography or postcon- often secondary to drugs, including NSAIDs. trast CT. It can be detected by renal arteriogra- Abnormal leakage from glomerular capil- phy; the renal cortex does not enhance after laries and an interstitial infiltrate lead to contrast injection while the medulla enhances. nephrotic syndrome and eventual renal failure. No contrast excretion is evident from abnor- In general, renal failure resolves after with- mal papillae. Magnetic resonance reveals a drawal of the offending agent, although deaths hypointense cortex on T2-weighted images. are reported. Prolonged renal failure developed in an adult with Henoch-Schönlein purpura after an epi- Drug Induced sode of macroscopic hematuria (125); histology revealed findings of tubulointerstitial nephritis. Renal toxicity is ascribed to numerous drugs, Some infections are associated with acute with some being anecdotal reports with little interstitial nephritis. proof. An increased risk of nephrotoxicity due The kidneys enlarge during the acute to long-term analgesic exposure is suggested by phase. Delayed postcontrast CT reveals corti- a number of studies. Yet one review concluded comedullary contrast enhancement due to vas- that although excessive use of phenacetin- cular and tubular stasis. Ultrasonography containing analgesics probably does cause renal detects diffusely hyperechoic cortices. The papillary necrosis and interstitial nephritis, no kidneys gradually decrease in size as the condi- convincing epidemiologic evidence exists that tion clears. non–phenacetin-containing analgesics (such as acetaminophen and aspirin) or nonsteroidal antiinflammatory drugs (NSAIDs) cause renal damage (124). Nevertheless, the literature con- Chronic Tubular Dysfunction tains numerous reports of an increased risk of Disorders nephrotoxicity from NSAIDs due to dehydra- tion, hypotension and resultant renal hy- Damage to renal tubules often also involves poperfusion, congestive heart failure, and adjacent interstitial tissue and vice versa. The underlying renal failure. The NSAIDs appear to major factor in renal failure, however, is tubular inhibit renal synthesis of prostaglandins. Nor- damage. From a prognostic viewpoint, tubular mally in low perfusion states the vasodilator injury progressing to tubular atrophy leads to a prostaglandins help prevent vasoconstriction permanent loss of renal function. and maintain renal blood flow, and in this setting the inhibition of prostaglandin produc- tion leads to renal failure and fluid retention. Renal Tubular Acidosis Other believed associations with NSAIDs The term renal tubular acidosis describes include acute tubulointerstitial nephritis, papil- several tubular transport disorders. Tradition- lary necrosis, and nephrotic syndrome. ally, it is subdivided into proximal and distal Patients with analgesic nephropathy lose types based on which nephron segment is renal volume bilaterally, and the kidneys involved, although such an approach is an develop an irregular outline. Papillary calcifi- oversimplification of the underlying pathop- cations are common. Even in the early stages of hysiology: analgesic nephropathy, CT detects papillary calcifications with a high sensitivity, and CT is Type I: defect in hydrogen ion secretion superior in detecting calcifications to US and (distal renal tubular acidosis) conventional radiography. Type II: defect involving bicarbonate reab- Even mannitol has led to acute anuric renal sorption (proximal renal tubular acidosis) failure in a setting of chronic renal failure due Type III: defects in both distal and proximal to diabetic nephropathy. renal tubules 657

KIDNEYS AND URETERS

Type IV: aldosterone deficiency and resist- renal failure; infected patients developing acute ance to aldosterone result in a hyper- renal failure have a high mortality. Severe lep- kalemic renal tubular acidosis tospirosis and severe malaria have led to acute renal failure. In general, renal tubular acidosis in child- Reversible acute oliguric renal failure is a rare hood has a congenital etiology, while in adults complication of nonfulminant hepatitis A infec- acidosis tends to be secondary to another con- tion in some patients. dition. The prevalence of renal cysts appears increased in type I renal tubular acidosis. Rhabdomyolysis Some children with vesicoureteral reflux also have renal tubular acidosis; growth failure in Rhabdomyolysis typically develops secondary these children probably is due to the renal to muscle compression, epilepsy, infection, tubular acidosis. ischemia, heat stroke, or trauma, and results in Patients with type I disease develop nephro- acute renal failure. Occasionally nontraumatic calcinosis. Aside from detecting nephrolithiasis rhabdomyolysis develops in a setting of diabetic and nephrocalcinosis and excluding other con- ketoacidosis. Presumably increased myoglobin ditions, imaging has a limited role in these levels are responsible for renal damage in this disorders. condition; myoglobin is a nephrotoxin. Renal tubular acidosis and decreased renal function result in decreased renal accumulation In Pregnancy of Tc-99m-DMSA and increased background activity. Such a renal pattern should lead to a Septic abortion used to be the main cause of search for an underlying defect. renal failure in pregnancy; currently preeclamp- sia and eclampsia are more common factors. In Cystinosis some women renal failure is multifactorial; thus chronic hypertension or acute pyelonephritis Nephropathic cystinosis results in renal tubular in a setting of preeclampsia should be conside- acidosis. red. Occasionally idiopathic postpartum renal The importance of detecting nephropathic failure develops. Chronic renal failure ensues in cystinosis lies in that effective therapy exists for some patients. cystine accumulation. A rare complication is HELLP syndrome (hemolysis, elevated liver enzymes, and low Tubulointerstitial Nephritis platelets) occurring during both pregnancy and puerperium. A major complication of this Medullary cystic disease, a type of tubulointer- syndrome is acute renal failure. In a pregnancy- stitial nephritis, was discussed earlier (see related acute renal failure study, HELLP syn- Congenital Abnormalities). drome accounted for 36%, postpartum Etiology of renal tubulointerstitial fibrosis hemorrhage for 26%, preeclampsia/eclampsia is unknown, although two peptides— for 15%, and abruptio placenta for 10% (126). transforming growth factor-b (TGF-b) and Hemolytic-uremic syndrome is a rare angiotensin II—appear to play a role. Also, both complication developing in pregnancy and interstitial fibroblasts and renal tubular epithe- postpartum. lium are involved in formation of an extracellu- lar matrix. Initially affected patients tend to be Diabetic Nephropathy asymptomatic, and the condition is often dis- covered only when advanced. The most common cause of chronic renal failure is diabetes mellitus. One should keep in Infection mind, however, that diabetic patients also develop renal stones, reflux, and infections, and Among unusual infections, Legionnaire’s in these patients voiding cystourethrography, disease has led to acute renal failure. Rocky urodynamic studies, and at times retrograde Mountain spotted fever, due to infection with pyelography are indicated to exclude related Rickettsia rickettsii, is associated with acute conditions. 658

ADVANCED IMAGING OF THE ABDOMEN

Initially the kidneys enlarge, but with time cular origin. The resistive index is related more shrink in size. A glomerulosclerosis ensues and to the site of disease than to the degree of renal eventually nephrotic syndrome and end-stage failure. A normal RI is found in most patients renal failure develop. with glomerulonephrosis, while patients with Pre- and postcontrast helical CT in type 2 dia- tubulointerstitial or vascular nephrosis have an betic patients reveal that both axial renal diam- increased resistive index. eters and arterial-phase cortical density are less Absent parenchymal uptake during scinti- in those with a nephropathy than in non- graphy with Tc-99m-MAG3 suggests acute nephropathic diabetics and controls (127); these glomerulonephritis. changes are related to the duration of disease. Patients with newly discovered glomeru- Once nephropathy is well established, US lonephritis probably should undergo chest identifies hyperechoic cortices. In patients with radiography not only to detect evidence of insulin-dependent diabetes mellitus but normal cardiac failure and effusions but also to estab- creatinine and blood urea nitrogen levels, lish a baseline appearance. Doppler US–derived renal interlobar artery RI is not sensitive enough in screening for Focal Segmental Glomerulosclerosis glomerular hyperfiltration. Focal segmental glomerulosclerosis is a syn- Glomerulonephritis drome resulting in chronic, progressive renal fibrosis. It is a common cause of renal disease. The subtypes of glomerulonephritis include Histology reveals sclerosis of some but not all membranous, immunoglobulin A (IgA)-related, glomeruli (hence the name). It does not appear vasculitis, and idiopathic. Systemic diseases to be an immune response. Most authors sub- associated with glomerulonephritis include a divide it into a primary form, with no dis- number of infections, polyarteritis nodosa, cernible cause, and a secondary form associated systemic lupus erythematosus, and Wegener’s with a number of diseases, including diabetes, granulomatosis.A minority of cirrhotic patients analgesic abuse, reflux nephropathy, a rejec- have glomerulonephritis ranging from mem- tion phenomenon, HIV-associated nephropa- branoproliferative to focal segmental and mem- thy, and, in some patients, renovascular hyper- branous. An infected ventriculoatrial shunt tension. Collapsing glomerulopathy is a variant can lead to glomerulonephritis, a condition of focal segmental glomerulosclerosis manifest- known as shunt nephritis. Even an occasional ing by the collapse of glomerular capillaries, patient with inflammatory bowel disease devel- marked podocyte enlargement, and associated ops proteinuria due to membranous glomeru- tubulointerstitial disease. lonephritis. Glomerulonephritis and nephrotic Clinically this entity manifests as nephrotic syndrome are associated with solid neoplasm syndrome and leads to progressive renal failure. paraneoplastic syndromes. Histopathology ty- It develops both in children and adults. pically reveals membranous glomerulone- Imaging plays a role mostly in detecting phritis. Proteinuria generally clears after tumor damage due to secondary causes.A hypertensive resection. patient developed unilateral focal segmental Renal enlargement is common in acute glomerulosclerosis associated with contralat- glomerulonephritis. Renal echogenicity varies, eral renal artery stenosis (128); the contralateral but often is greater than in the adjacent kidney presumably was spared glomeruloscle- liver. Echogenicity decreases with clinical rosis by the renal artery stenosis. The patient’s improvement. renal insufficiency resolved after renal artery Chronic glomerulonephritis leads to a stenosis repair, suggesting renovascular hyper- gradual loss of renal parenchyma. Only a tension as the primary cause for focal segmen- faint but persisting nephrogram is identified tal glomerulosclerosis. post–contrast injection. Eventually the kidneys Therapy of any underlying condition is gen- become small, smooth, and hyperechoic, similar erally instituted. Corticosteroids are often used to other end-stage renal disease. to treat patients with idiopathic focal segmental Color Doppler US is helpful in distinguishing glomerulosclerosis, despite a lack of evidence glomerular nephropathy and disorders of vas- for such therapy. The eventual therapy is renal 659

KIDNEYS AND URETERS transplantation. Focal segmental glomeru- tion–associated nephropathy and cyclosporine losclerosis patients who receive a cadaveric nephrotoxicity. These patients also develop transplant have a significantly higher graft loss sepsis, hypotension, and other related complica- rate than those with a human leukocyte antigen tions, and often renal failure is multifactorial. (HLA)-identical living-related transplant. Nephrotic Syndrome Hemolytic-Uremic Syndrome Nephrotic syndrome is an end-stage condition A number of bacterial and viral infections are induced by a number of entities. Clinically it associated with hemolytic-uremic syndrome. manifests by hypoproteinemia, proteinuria, and Thus enterohemorrhagic E. coli infection causes hypercholesterolemia. both hemorrhagic colitis and hemolytic-uremic Nephrotic syndrome is an occasional mani- syndrome. Some patients recover with medical festation of neoplastic disease. Patients with therapy, including hemodialysis. In children, thymoma are prone to developing a nephrotic E. coli–induced hemolytic-uremic syndrome syndrome, ranging from minimal histologic and resultant renal failure are common factors change in some to focal segmental glomeru- leading to kidney transplantation. lonephritis, proliferative glomerulonephritis, Scleroderma renal crisis is a rare cause of and membranous glomerulopathy. Such diverse acute renal failure due to microvascular disease conditions as systemic amyloidosis, lupus ery- and other factors. thematosus, and renal vein thrombosis can Doppler US reveals an increase both in RI and manifest as nephrotic syndrome. Some pati- PI. Renal artery flow is decreased. Renal volume ents with renal vein thrombosis are asympto- is increased. matic,with imaging offering a clue to the under- lying condition; the involved renal vein is Cirrhosis/Hepatorenal Syndrome widened by a thrombus and the affected kidney is enlarged. Increased renal vascular resistance (RI) devel- Patients with nephrotic syndrome undergo- ops in patients with progressive cirrhosis. Even ing bicarbonate hemodialysis have developed in patients with Child’s class A cirrhosis without extensive metastatic calcifications throughout ascites, renal RI is increased (>0.7) in about a the body. These calcifications are detected by third of patients (129). A greater increase in scintigraphy. both RI and PI occurs in those with Child’s B and C cirrhosis. On the other hand, 99mTc- DTPA renography identifies a reduced glomeru- Miscellaneous Conditions lar filtration rate only in more advanced cirrhosis and Doppler US detects earlier than Medullary Sponge Kidney renography those cirrhotic patients at higher risk of developing renal failure. Medullary sponge kidney, or tubular ectasia, Hepatorenal syndrome consists of renal refers to cystic collecting tubule dilation (ducts failure in association with severe liver disease. of Bellini) and is believed to be a congenital dis- The mortality rate is high once this syndrome is order, although usually manifesting in adult- established. hood. It ranges from focal to generalized. In a minority of patients it is associated with Post–Bone Marrow Transplantation calcifications within collecting tubules. Tubular ectasia is the early hallmark of this Acute renal failure is a recognized complication condition, identified by IV urography as con- after bone marrow transplantation. On an acute trast-filled streaks opacifying renal pyramids basis tumor lysis syndrome and marrow- before or simultaneously as adjacent calyces infusion–associated toxicities occur. Veno- (Fig. 10.32).A clear border tends to be preserved occlusive disease leading to hepatorenal-like between the abnormally opacified papillae and syndrome occurs within about 1 month and is calyces. At times faint calcifications develop. a common cause of acute renal failure. Late This condition should be differentiated from a failure includes bone marrow transplanta- normal postcontrast papillary blush, seen as a 660

ADVANCED IMAGING OF THE ABDOMEN

eventual residual blunted calyx (Fig. 10.33). Calcifications develop in the papillary region. Either a portion or the entire papilla is involved; necrosis involves either one or several papilla; it is either unilateral or bilateral. Papillary necrosis should be differentiated from medullary sponge kidney. Radiation Nephritis Damage occurs directly to the renal tubules and glomeruli and is due to radiation vas- culitis. Some patients develop renal failure or hypertension. A sufficient radiation dose results in a shrunken kidney. The renal outline becomes irregular. Damage is limited to the radiation port. Amyloidosis Both primary and secondary amyloidosis affect Figure 10.32. Renal tubular ectasia is identified as barely per- ceptible streaks of contrast (arrows) in the papillary regions the kidneys. Affected patients are prone to during an IV urogram. developing renal vein thrombosis, and the sudden onset of nephrotic syndrome should suggest this diagnosis. Renal failure is common in patients with extensive renal amyloidosis. homogeneous papillary enhancement. Some Benign lymph node hyperplasia (Castleman’s authors use the term benign tubular ectasia to disease) is associated with renal amyloidosis. designate early findings and to differentiate Occasionally a patient with Crohn’s disease them from more advanced medullary sponge and renal amyloidosis develops nephrotic kidney, but whether such early findings indeed syndrome. are part of a spectrum of medullary sponge Initially the kidneys enlarge, but in time kidney is not clear. cortical atrophy ensues and the kidneys Occasionally similar findings are detected shrink. Focal amyloid infiltration mimics a with CT and MR. Ultrasonography shows neoplasm. Occasionally scattered, amorphous increased echogenicity if renal pyramid calci- calcifications develop. At times US reveals a fications have developed. prominent medulla and a hyperechoic renal parenchyma. Papillary Necrosis Lupus Nephritis The term papillary necrosis describes specific damage to the papilla detected by imaging. Lupus nephritis is a manifestation of systemic Common conditions associated with papillary lupus erythematosus. These patients develop a necrosis include analgesic and NSAID abuse, nonspecific sclerotic change and immunoglob- diabetes mellitus, some infections, and sickle ulin deposition within glomerular small arte- cell anemia. The final pathway probably is rioles and capillaries. A patient with lupus ischemia. Findings develop either acutely or on erythematosus who develops a nephrotic syn- a chronic, indolent basis. drome should be investigated for renal vein Imaging findings tend to be rather specific thrombosis. and are best seen with IV pyelography: papillary Renal Doppler US is useful in these patients. erosions, necrosis, sloughing, and eventual A normal RI predicts a better renal outcome passage of necrotic debris distally, with an regardless of creatinine level. 661

KIDNEYS AND URETERS

B

A

Figure 10.33. Papillary necrosis.A: Excretory phase CT shows contrast collections in papilla (arrows). Coronal maximum intensity projection (B) and multiplanar reformatted images (C) confirm bilateral involvement. (Source: Joffe SA, Servaes S, Okon S, Horowitz M. Multi-detector row CT urography in the evaluation of hematuria. RadioGraphics 2003;23(6):1441–1456, with permission from the Radiological Society of North America.) C

Pseudoxanthoma Elasticum in the renal cortex. Thus conditions associ- ated with intravascular hemolysis and the Ultrasonography in pseudoxanthoma elasti- resultant renal cortical iron storage produce a cum reveals highly reflective foci in the renal hypointense cortical signal on T2-weighted parenchyma. While this finding is suggestive of MRI. pseudoxanthoma elasticum, it is not pathogno- monic and is also found in other conditions. Intravascular Hemolysis Dialysis-Associated Hemoglobin from intravascular hemolysis Findings is bound to plasma proteins and metabolized by the liver. Excess unbound hemoglobin is Using typical doses of gadolinium contrasta- filtered by the kidney, some is excreted, gents in dialysis patients, 79% of the contrast and some is reabsorbed by tubules and stored agent was dialyzed after the first dialysis and 662

ADVANCED IMAGING OF THE ABDOMEN

99.6% after the fourth (130); the authors con- occasionally developing even in children. clude that being on hemodialysis is not a con- Some malignant-appearing tumors histologi- traindication for the use of these contrast cally exhibit growth patterns suggesting a agents. benign tumor, including renal cell carcinomas and urothelial carcinomas. Some surveys suggest that especially young patients under- Dialysis-Acquired Cysts going prolonged dialysis who develop renal cysts are prone to renal cell carcinomas and A better name for this condition is acquired they should undergo regular screening by cystic disease of the kidney because the onset of imaging. cysts begins in patients with chronic renal Early postcontrast helical CT achieved a 96% failure even before dialysis is started.A common sensitivity and 95% specificity in detecting a condition in patients with end-stage renal carcinoma in chronic hemodialysis patients, disease undergoing long-term hemo- or peri- while delayed images had an 83% sensitivity toneal dialysis, cyst prevalence increases with and 94% specificity (131); early postcontrast duration of dialysis. Why these cysts form is not images revealed significant enhancement differ- known, but they tend to involute after renal ences between carcinoma and adjacent renal transplantation. Some of these cysts from parenchyma, a finding not seen on delayed dialysis patients are lined with cuboidal images. epithelium. Most patients with these cysts are asympto- matic. Pain and hematuria are mostly due to Other Findings cyst rupture and bleeding. Imaging of these often small, distorted Urinary stones are uncommon in native native kidneys is difficult, especially with US. kidneys in these patients, presumably due to Computed tomography using IV contrast is their decreased urine production, but renal feasible if the patient is on dialysis. These calcifications are common. patients are at increased risk of developing On rare occasions emphysematous pyelon- renal cell carcinoma, and any contrast enhance- ephritis develops in a nonfunctioning renal ment suggests a malignancy. Imaging detects allograft of a diabetic patient. numerous cortical cysts in a small kidney. Intra- Mesenteric ischemia appears to be more cystic hemorrhage and its sequelae tend to common than expected in patients with end- mimic a neoplasm. Cyst wall calcifications stage renal disease. develop, presumably from prior hemorrhage, but limited urinary output makes kidney stones uncommon. Magnetic resonance imaging is an alternative Pyeloureteritis Cystica imaging modality. The content of some cysts is Of unknown etiology but probably due to hyperintense on T1-weighted MRI due to past degeneration, pyeloureteritis cystica consists of hemorrhage. No enhancement is evident numerous fluid-filled cysts in the collecting post–MR contrast, thus differentiating these system or ureter wall. Associated chronic infec- cysts from neoplasms. tion is common. It is not premalignant. The con- Eventually the imaging appearance appro- dition is generally detected incidentally. aches that seen with autosomal-dominant poly- Imaging shows multiple small, uniform size, cystic disease, but unlike polycystic disease and round soft-tissue tumors in a ureter or renal these patients do not develop cysts in other pelvis (Fig. 10.34). Occasionally malacoplakia is organs. in the differential diagnosis, but tumors in the latter condition tend to be more irregular in Malignancies outline and the involved ureter somewhat dilated—findings not seen in pyeloureteritis Long-term dialysis is associated with several cystica. Ureteral varices tend to be more serpig- benign and malignant renal neoplasms, inous in appearance. 663

KIDNEYS AND URETERS

Hematoma Spontaneous nontraumatic subcapsular or perirenal hemorrhage, also called Wunderlich syndrome, is not common. Clinically, an under- lying neoplasm or bleeding diathesis needs to be excluded, although occasionally polycystic kidneys, a vasculitis, glomerulonephritis, or pyelonephritis is responsible. Computed tomography or angiography should suggest an etiology for most of these hematomas. Acute hemorrhage may hide an underlying neoplasm, and some of these pa- tients require exploration or follow-up study after the hematoma resolves. Abscess Most perinephric abscesses are associated with renal or adjacent organ infection. Some abscesses are confined by Gerota’s fascia, while others extend into the adjacent retroperitoneal structures. Most of these abscesses are readily detected with imaging. An occasional perinephric abscess mimics a neoplasm. Figure 10.34. Ureteritis cystica. Ultrasonography of a perinephric abscess often reveals a complex fluid collection. These abscesses can be successfully drained during laparoscopy, although many are drained percutaneously. Perinephric Conditions Tumors Thickening Similarly to infection, tumors spread readily in the perirenal space. Most primary tumors are of The right anterior extrarenal space extends mesenchymal origin. Lymphoma either involves from the perirenal fascia to the liver capsule. this space diffusely, with little displacement of Conditions that widen this space and are hyper- adjacent structures, or develops in a nodular echoic include acute inflammatory conditions pattern. A similar diffuse involvement is also such as pancreatitis, appendicitis, acute cholan- occasionally found with metastatic melanoma. gitis, adjacent abscess, ischemic bowel disease, Differentiation from an adrenal tumor can be and even a penetrating ulcer. An increased difficult. width with normal echogenicity is seen with A diagnosis of perirenal lymphoma is not chronic inflammation, peritoneal metastases, always straightforward; at times even a needle previous surgery, and steroid therapy. Left biopsy is not diagnostic. perirenal fat necrosis develops with severe pan- creatitis; CT and MR reveal a fat-containing infiltrate mimicking a retroperitoneal tumor, Vascular Disorders but associated pancreatic findings should suggest the correct diagnosis. Arteriovenous malformations and heman- Urinomas and lymphoceles are discussed in giomas were discussed earlier (see Vascular Chapter 14. Tumors). 664

ADVANCED IMAGING OF THE ABDOMEN

Ischemia nario, if nonenhanced CT does not reveal an abnormality to explain the patient’s clinical One result of renal ischemia is renovascular findings, a postcontrast CT is indicated to eval- hypertension (discussed in Chapter 17), but in uate for a possible renal infarct. some patients ischemia manifests primarily as Postcontrast CT of a total infarct shows a renal failure (also called ischemic nephropathy). hypodense, nonfunctioning kidney. Prominent Also, renal artery stenosis is but one etiology of capsular collaterals, called the cortical rim renal ischemia, with other etiologies being sign, often lead to surrounding vascular vessel compression by extrinsic tumors, enhancement. A focal infarction appears as a artery thrombosis, emboli, vasculitides, and wedge-shaped region of decreased or absent venous occlusions. Major renal vein obstruction contrast enhancement with sharply defined eventually leads to the ischemia–renal failure margins, most often extending to the capsule. cycle but not to hypertension. In addition, Ultrasonography reveals a wedge-shaped renal vein obstruction has different imaging hypoechoic region. Eventually the involved manifestations. parenchyma atrophies, a scar forms, and an Renal ischemia is incompletely understood. irregular renal outline remains as evidence of Normal kidneys receive more blood than neces- prior infarction. sary for functioning and tolerate considerable Early intraarterial fibrinolysis therapy is indi- underperfusion as long as systolic blood pres- cated if recovery is anticipated. Renal ischemic sure is above 70 or 80mmHg or so. Ischemia is due to renal artery stenosis is treatable by less common in a setting of fibromuscular dys- angioplasty (discussed in Chapter 17). plasia than with atherosclerotic disease. A sufficient decrease in renal blood supply, Nephrosclerosis regardless of etiology, will evolve into renal infarction. Acute infarction has developed in Arteriolar spasm, endothelial spasm, muscle Behçet’s disease, primary renal artery dissection hypertrophy, and eventual fibrosis develop or thrombosis, cocaine abuse, and a subcapsular in hypertension-induced nephrosclerosis. The hematoma secondary to metastasis to the final pathway is renal ischemia. Proteinuria is kidney,and has even been idiopathic.In a setting common. If untreated, renal failure ensues. The of renal artery stenosis, acute renal failure has kidneys gradually shrink and cortical thinning developed after some medications, including becomes evident. Calyces are not affected. diuretics and other antihypertensive drugs. Clinically, acute nontraumatic renal artery thrombosis and resultant ischemia typically Immunosuppression/Acquired manifest by sudden onset of flank pain. On a Immunodeficiency Syndrome more chronic basis decreased arterial flow is less symptomatic, and some of these patients simply General develop a small, nonfunctioning kidney. The onset of flank pain due to acute renal Renal abnormalities are common in HIV- ischemia/infarction mimics that of renal colic. infected patients. Ultrasoaography findings Among 300 patients admitted with renal colic, cousist of enlarged kidneys, decreased corti- renal parenchymal infarction was eventually comedullary definition, decreased renal sinus diagnosed in three patients (132). fat, and a heterogeneous parenchyma, some Intravenous urography of acute renal artery with hyperechoic striations (133). In general, obstruction reveals a nonfunctioning but increased renal insufficiency in AIDS patients is normal-sized kidney. Ultrasonography also associated with pelvocalyceal thickening and a shows a normal kidney. No major renal blood hyperechoic appearance. flow is identified with Doppler US. In such a Cerebral toxoplasmosis in AIDS patients is clinical setting postcontrast helical CT or treated with sulfadiazine, which is associated angiography simply confirms the diagnosis. with acute renal failure due to sulfadiazine- Computed tomography performed without induced crystalluria. Ultrasonography findings contrast in a search for calculi will miss renal consist of hyperechoic foci in renal parenchyma arterial ischemia. Thus in such a clinical sce- and hyperechoic debris in collecting systems. 665

KIDNEYS AND URETERS

Stones and hydronephrosis also develop in these rare patients have also received both kidney and patients. bone marrow transplantation; these dual trans- The HIV-infected patients on indinavir plants are not discussed in this book. sulfate therapy, a protease inhibitor used to treat HIV infection, develop ureteral obstruction due Pretransplant Donor Evaluation to nonopaque indinavir crystals. An occasional AIDS patient develops a spon- Preoperative donor kidney evaluation is perfor- taneous perinephric hematoma. med to detect accessory renal arteries and other anomalies.In a setting of multiple renal arteries, donor renal artery reconstruction rather than Infection ligation preserves renal mass. Although gener- Similar to other sites, renal infection with ally not affecting gross renal function,ligation of Pneumocystis carinii, aspergillus abscess, cyto- accessory renal arteries tends to be associated megalovirus, and other unusual organisms with focal renal infarction. develop in these patients. Some of these infec- Horseshoe kidneys are used for transplanta- tions eventually evolve into multiple, punctate tion. When possible, a horseshoe kidney is parenchymal calcifications. Focal mucormyco- divided at the isthmus and the halves are trans- sis mimics a renal neoplasm. planted into two recipients. Part of a living donor horseshoe kidney can be used. Traditionally, renal vasculature was evaluated Tumor with angiography, a role partially supplanted by CT and now by MRA. Intraarterial DSA achieves Simple renal cysts are considerably more over 95% sensitivity and specificity in detecting prevalent in children with AIDS that in normal accessory renal arteries in kidney donors. children. Other abnormalities detected by arteriography Renal involvement with lymphoma is include fibromuscular dysplasia and atheroscle- common in AIDS. Even rarer lymphomas rosis, findings often affecting planned surgery. develop, such as a non-Hodgkin’s angiocentric Preoperative CT and MRA in living renal renal lymphoma, which shows a propensity to donors detect essentially the same number of invade and destroy small vessels. renal arteries, with disagreement primarily Renal leiomyosarcomas develop in HIV- among several-millimeter-diameter accessory infected patients, including children. vessels (134). Multislice helical CT with trans- verse, coronal, and 3D reconstructions detects most accessory arteries and early branching and Postoperative Changes defines other relevant anatomy, but these are rather technically complex studies requiring Kidney Transplantation close attention to detail. Gadolinium enhanced MRA correctly An uncommon indication for renal transplanta- identifies the arterial supply to native kidneys tion is bilateral, and synchronous renal cell (including accessory renal arteries), most prox- cancers requiring bilateral nephrectomies. imal arterial branches and some anomalous These patients undergo bilateral nephrec- draining renal veins (135,136). Addition of MIP, tomies, a waiting period of several years on volume rendering and SSD algorithms may dialysis follows, and then they undergo renal improve image presentation, but they do not transplantation. Such an approach is undoubt- improve accuracy. MRA can also evaluate renal edly uncommon; most patients with early and size and fetal lobulations without the potential low-grade renal cell carcinomas undergo partial angiography complications. Reported sensitivi- nephrectomies. ties of detecting accessory renal arteries range An occasional patient receives both a kidney from 75% to 100%, with the latter being rather and a pancreas transplant; the consequences of optimistic. Also the ability of MRA to detect the transplanted pancreas, with its exocrine fibromuscular dysplasia is not established. secretions draining into the bladder, are dis- Reported Doppler US sensitivities in detect- cussed in Chapter 9.For a number of indications ing accessory renal arteries range up to 100%, 666

ADVANCED IMAGING OF THE ABDOMEN but these studies are plagued by low include ureteral or bladder fistulas, bladder specificities. outflow obstruction, ureteral stones, and lym- MR urography can potentially detect urinary phoceles. Transplantation complications can be collecting system abnormalities in living renal divided into early and late. Early ones include donors. Whether the technique is sufficiently rejection, urine leaks, and obstruction. The accurate in actual practice to detect ureteric major late complication is renal artery stenosis. duplications and other relevant anomalies is not Posttransplant drug therapy can result in clear. hypersplenism and portal hypertension; these patients present with splenomegaly and Transplantation thrombocytopenia. Whether a voiding cystourethrogram is per- formed in transplant recipients prior to renal Imaging transplantation varies between institutions. Because most transplanted kidneys are located Some believe this study adds little value. rather superficially, gray-scale US can be per- Some children requiring renal transplanta- formed with a higher resolution transducer tion also have bladder dysfunction, such as pos- than usual. As a result, better anatomic detail is terior urethral valves, a neurogenic bladder, achieved than is possible with a native kidney. or vesicoureteral reflux, and augmentation Regions of decreased color on color Doppler cystoplasty is added either before or after US scans in a transplanted kidney appear to be transplantation. related to focal perfusion abnormalities. Such With the exception of small children, the focal hypoperfusion regions include infections, transplanted kidney is nearly always placed in arteriovenous fistulas, a kinked artery, and the iliac fossa, extraperitoneal in location. Here severed accessory arteries. the kidney is close to major vessels and bladder A color Doppler US finding of a significant and is supported by surrounding structures. A decrease in interlobar artery blood flow, but side-to-end arterial anastomosis goes to the with no flow changes in segmental arteries, external iliac artery and an end-to-side venous suggests acute rejection. Decreased interlobar anastomosis goes to the external iliac vein. The artery blood flow is also found in renal artery left iliac fossa is used if a second transplantation stenosis and interstitial edema. is necessary; third transplantations are high in One subset of patients consists of those with the right iliac fossa. an oligoanuric allograft suspected to be due to Renal transplantation is feasible in patients either severe rejection or renal artery or vein infected with Schistosoma haematobium.Pre- thrombosis. Both Tc-99m-DTPA scintigraphy transplant antischistosomal chemotherapy con- and color Duplex US can differentiate minimal trols posttransplant schistosomal infection; the and not perfused renal allografts. increased risk for bladder cancer in these Contrast-enhanced MRI can differentiate patients justifies close follow-up. between graft kidneys with normal function, mild dysfunction, and severe dysfunction. Mag- Posttransplant Evaluation netic resonance imaging in transplant patients Clinical with normal renal function typically shows an expected postcontrast increase in signal inten- Rough data from several sources suggest that sity of the renal cortex and medulla, followed by first-year posttransplant mortality is about 4%, a signal intensity decrease in the medulla. mostly due to infection; transplanted kidney Patients with acute allograft rejection have less loss ranges from 5% to 10%, mostly due to rejec- postcontrast increase in cortical signal intensity tion, with a subsequent graft loss of about 5% than those with normal allografts.Magnetic res- per year. The half-life of transplanted kidneys onance imaging cannot, however, differentiate varies widely, depending on donor compatibil- between normal, acute rejection and acute ity and whether a living donor kidney or a tubular necrosis, but MRA can evaluate renal cadaver kidney is used. artery anatomy (Fig. 10.35). The most common direct surgical complica- Scintigraphy evaluates function in a trans- tion is ureteral obstruction.Other complications planted kidney. A Tc-99m-MAG3 renogram 667

KIDNEYS AND URETERS

A B

Figure 10.35. A,B: Volume-rendered MRI of normal renal trans- plant arteries. C: Thresholding eliminates renal parenchyma and highlights arteries. (Source: Hohenwalter MD, Skowlund CJ, Erickson SJ, et al. Renal transplant evaluation with mr angiogra- phy and mr imaging. RadioGraphics 2001;21:1505–1517, with permission from the Radiological Society of North America.) C

appears useful in determining renal transplant Postural drainage stasis occasionally devel- prognosis during the postoperative period. ops in a transplanted kidney. Postural stasis can Initial tracer uptake is decreased or absent be evaluated by varying the patient position with transplant dysfunctions such as acute during Tc-99m-MAG3 imaging. tubular necrosis, acute rejection, and an Carbon dioxide angiography is feasible in a obstruction than in normally functioning ones. transplanted kidney. Major stenoses, arteriove- A focal photopenic defect in a renal transplant nous shunting, and diffuse arterial disease can suggests tubular injury. Similarly, Tc-99m- be evaluated (137), although insufficient data MAG3 transit time is prolonged in obstructive preclude establishing a specific role to this kidneys. modality. 668

ADVANCED IMAGING OF THE ABDOMEN

Rejection Using surface coils, adiabatic excitation pulses and in vivo phosphorus MR spec- Differentiation between acute tubular necrosis troscopy, phosphorus-31 MR spectroscopy and acute rejection is of obvious importance, appears to have a role in detecting and possibly but imaging provides only limited assistance, differentiating rejection and acute tubular and a biopsy is generally necessary to evaluate necrosis. Patients with rejected kidneys have a graft dysfunction and distinguish between these higher inorganic phosphate-to–a-adenosine two. Biopsy complication rates are low, although triphosphate ratio than controls and a reduced bleeding, pseudoaneurysm formation, or an pH (140). Rejection and tubular necrosis could arteriovenous fistula do form if an adjacent be differentiated from each other by pH. These artery or vein is injured. findings need to be placed in a larger clinical Acute tubular necrosis is due to transplanta- perspective. tion-associated ischemia and occurs within a Scintigraphy in acute rejection reveals day or so. Acute rejection occurs from the decreased perfusion, a finding also seen in other time of surgery to several months after trans- complications. An initial study shortly after the plantation. Rejection leads to renal swelling, a transplant is useful in establishing a baseline. finding seen with other complications. Viral Xenon-CT is used to study cerebral per- infections are often in the differential diagnosis; fusion; it can also measure regional blood flow some, such as Epstein-Barr viral infections, are in a transplanted kidney. Although differences associated with lymphoproliferative disorders in perfusion exist between normal kidney and are detected with a polymerase chain medulla and cortex, these perfusion differences reaction. are less evident in patients with chronic Doppler US appears helpful in monitor- rejection. ing rejection. The pulsatility index, which is dependent on flow resistance, increases with rejection and in some hands when combined Vascular Complications with peak arterial systolic velocity and acceler- Arterial Stenosis ation index achieves a high sensitivity and specificity in differentiating a normally func- Posttransplantation hypertension is common. tioning transplant from a hypofunctioning one. In about one third or so of these hypertensive Others, however, find that Doppler US cortical patients their hypertension is related to renal vascularity data do not correlate with rejection, artery stenosis. The prevalence of renal artery and even severe transplant rejection can be stenosis is more common in cadaveric donor associated with normal vascularity (138). In kidneys compared to living donor kidneys. This children with chronic rejection, power Doppler stenosis-associated hypertension can be treated US using a high-frequency and high-resolution medically, by angioplasty, or by surgical revas- transducer (13MHz) found irregular and cularization. narrow interlobular vessels, in distinction to Stenoses occur at the anastomosis, distal to children with chronic rejection who have a pal- the anastomosis (donor artery), or, least isade-like appearance (139); the authors ascribe common, proximal to the anastomosis in the their results to use of a high-frequency trans- recipient’s artery (Fig. 10.36). Stenosis may be ducer, which was possible because of decreased related to surgery or may be part of rejection. It tissue thickness in children. can recur after angioplasty. Postcontrast MRI holds promise in differen- Acceleration time, obtained with Doppler US, tiating transplant rejection from acute tubular is prolonged with a significant proximal arterial necrosis. Magnetic resonance signal intensity stenosis, although the clinical accuracy in data after contrast injection shows that in detecting arterial stenosis varies depending on patients with transplant rejection the time to the assumed threshold. Another measure is peak intensity in the renal cortex and medulla transplant artery peak systolic velocity, but here are longer than in patients with normal grafts; also results have been inconsistent. Peak systolic in patients with acute tubular necrosis, on the velocity varies considerably even without a other hand, renal cortex and medulla times are stenosis, although use of the iliac artery as a similar to normal. standard is helpful. 669

KIDNEYS AND URETERS

A B

Figure 10.36. Renal artery stenosis in a transplanted kidney.A: Initial arteriogram reveals a tight stricture (arrow).B: Lumen is patent after dilation. (Courtesy of Oscar Gutierrez, M.D., University of Chile, Santiago, Chile.)

Magnetic resonance indications in suspected Arterial Thrombosis renal artery stenosis continue to increase and gadolinium-enhanced MRA is assuming a The etiologies of renal artery throm- major role in detecting transplanted renal bosis occurring shortly after transplantation artery stenosis, in some studies achieving sensi- include hypotension, renal artery stenosis, tivities of >85% and specificities approaching graft rejection with extensive arteriolar 100% and in some patients even being superior occlusions, and retrograde renal artery throm- to DSA. Depending on the sequences adopted bosis, or it may be related to the surgical and the type of reconstruction, transplant procedure. artery stenoses, renal vein thromboses, extrin- Neither arterial nor venous flow is de- sic compression, and perfusion deficits are tected with Doppler US distal to a complete identified with varying degrees of accuracy (Fig. occlusion. 10.37). The relative roles for color Doppler US and MRA are not settled, but MRA appears to Vein Occlusion slightly overestimate renal artery stenosis while color Doppler US is more prone toward false- The consequences of renal vein thrombosis are positive results. similar to those of renal artery thrombosis Posttransplant renal artery stenosis is because the transplanted kidney has no addi- amenable to percutaneous transluminal angio- tional collateral veins. plasty, and in a number of institutions angio- In the absence of proximal renal artery steno- plasty is the procedure of choice for this sis, Doppler US findings suggestive of partial complication. In experienced hands complica- venous occlusion after transplantation include tion rates are low. Surgical revascularization the presence of small amplitude arterial wave- is indicated if angioplasty is unsuccessful, forms but with diastolic flow still present; with although a restenosis after angioplasty can be complete renal vein obstruction no venous flow treated with an endoluminal stent placed across is evident and diastolic flow in the renal artery the site of restenosis. is reversed. 670

ADVANCED IMAGING OF THE ABDOMEN

B A

Figure 10.37. Fibromuscular dysplasia 4 years after renal trans- plant. A,B: Volume-rendered MRI reveal an irregular, beaded appearance to the renal artery. C: CO2 angiography also reveals similar changes. (Source: Hohenwalter MD, Skowlund CJ, Erickson SJ,et al.Renal transplant evaluation with MR angiography and MR imaging. RadioGraphics 2001;21:1505–1517, with permission C from the Radiological Society of North America.)

Vascular Fistula Ureter Complications Renal pelvic and ureteral complications develop The gold standard in detecting vascular fistulas in roughly 10% to 15% of patients undergoing is arteriography. Doppler US detects only some renal transplantation and include obstruction, of these fistulas and early-phase contrast CT necrosis, and urinary fistula. They are more should be considered in a setting of normal common in a setting of multiple donor kidney Doppler US but clinical suspicion of a fistula. renal arteries. Urinary obstruction occurs These fistulas are successfully occluded with roughly equally in living-related donors and transcatheter embolization; nevertheless, the cadaveric donors, but leakage is more common complication rate is high even after successful in living donors. Ureter complications are embolization and includes renal artery occlu- managed with a percutaneous nephrostomy, sion and major hemorrhage necessitating a transurethral bladder drainage, or drainage of nephrectomy. fluid collections. 671

KIDNEYS AND URETERS

Magnetic resonance imaging appears to patients who develop ureteral stenoses or have a role in evaluating posttransplant ureter fistulas is shorter than in those without these complications. Similar to the bile ducts, MR complications. images mimicking conventional urography are Most urinary extravasations occur at the feasible. In patients with suspected urologic ureteral anastomosis and result in a urinoma abnormalities, MR urography identifies dilated (Figs. 10.39 and 10.40). Some leaks are second- renal pelves and detects ureteral leaks and ary to ureteral necrosis, presumably ischemic in obstructions. origin, and are difficult to treat. Ureteral obstruction develops secondary to Ultrasonography detects most urinomas. postoperative edema, anastomotic stricture, Scintigraphy during the acute time period kinking or compression by an extrinsic shows radiotracer activity in the urinoma. urinoma, hematoma, or lymphocele (Fig. 10.38). A posttransplant leak is approached with a The ureteroneocystostomy is the most common percutaneous nephrostomy and antegrade site of obstructions. A ureter can be trapped in placement of a nephroureteral stent; leaks that an obturator hernia. Because of denervation, do not heal require surgical repair. posttransplant patients manifest obstruction Ureteral complications requiring reconstruc- simply by worsening renal function. With a tion range from complete ureteral necrosis to stenosis, US or scintigraphy should detect any long or multiple ureteral strictures. Most often underlying hydronephrosis, but keep in mind with ureteral necrosis a part of the bladder is that dilation is not always secondary to an used as a substitute, although an artificial ureter obstruction. has also been successfully employed. Posttransplant ureteral obstructions are treated with ureteral balloon dilation and Fluid Collections antegrade placement of nephroureteral stents; about two thirds of those with early obstruction Postoperative fluid collections are common are treated successfully, but the success rate and range from hematoma, seroma, urin- decreases in those with late obstruction. oma, and lymphocele, to an abscess. Most Obstruction can also be relieved with a per- small hematomas and lymphoceles resolve cutaneous nephrostomy. Only a minority of spontaneously. patients eventually require open surgery. Many of these fluid collections have a similar In general, the survival of a renal graft in gray-scale US appearance, and fluid aspiration

A B

Figure 10.38. Percutaneous nephrostogram of a transplanted kidney with an obstructed ureter.A: A proximal leak is evident (arrow) in a more distally obstructed ureter. B: A catheter has been advanced through the obstruction. (Courtesy of David Waldman, M.D., University of Rochester.) 672

ADVANCED IMAGING OF THE ABDOMEN

A B

Figure 10.39. Urinoma after renal transplant. Three excretory phase CT images through the kidney (A), slightly inferior (B), and even more inferior (C) reveal contrast extravasation (arrow). (Courtesy of Nancy Curry, M.D., Medical University of South C Carolina.)

B A

Figure 10.40. Urine leak after renal transplantation 1 week earlier. A: CT shows a fluid collection medial to the ureteropelvic junc- tion (arrow). B: Dynamic renal scintigraphy using Tc-99m-DMSA identifies progressive tracer accumulation in this region (arrows). (Source: Titton R, Gervais DA, Hahn PF,Harisinghani MG, Arellano RS, Mueller PR. Urine leaks and urinomas: diagnosis and imaging- guided intervention. RadioGraphics 2003;23:1133–1147, with permission from the Radiological Society of North America.) 673

KIDNEYS AND URETERS is necessary to differentiate between them. A plant patients have changed considerably; hematoma initially is hyperechoic,but gradually central nervous system involvement predomi- becomes hypoechoic and eventually anechoic. nated initially, during the cyclosporine era A seroma, urinoma, and lymphocele are all thoracic and abdominal sites were more hypointense on T1- and hyperintense on T2- common, while isolated involvement of the weighted MRI. Significant urinomas usually transplanted kidney is now more evident. Cur- require reoperation. rently lymphoproliferative disorders most often Lymphoceles develop from the disruption present as solitary or multiple tumors, often of pelvic lymphatics. They tend to become limited either to the allograft or allograft hilum multiseptated. Therapy of these posttransplant (142); most are extranodal in location. Newer lymphoceles includes open or laparoscopic immunosuppression agents are evolving, and marsupialization, percutaneous drainage, and the type of neoplasms encountered in different percutaneous injection of a sclerotic agent. studies reflects, in part, the immunosuppressive External drainage has a high failure rate, but approach used. percutaneous sclerotherapy using a povidone- Lymphoproliferation ranges from a non- iodine agent is a simple technique and has had specific mild adenopathy to malignant lym- considerable application; recurrent lymphoce- phoma. B-cell non-Hodgkin’s lymphoma is les can be retreated percutaneously. Laparo- most common, but other lymphomas are also scopic marsupialization with internal drainage encountered. In general, these lymphomas tend is feasible, and effective therapy for posttrans- to be more aggressive than their counterparts in plant lymphoceles but is more invasive. Intra- nonimmunosuppressed individuals. operative US guidance is often helpful. Transplant patients develop renal cell carci- nomas in the native kidneys and in the renal Stones allograft and ovarian carcinomas. No signifi- cant relationship exists between the prevalence The frequency of urinary calculi in a trans- of renal cell carcinoma and the presence of planted kidney ranges up to 3%, a prevalence acquired cystic kidney disease, patient age, type greater than in the general population. About and duration of dialysis, or drugs used. Screen- half of these stones are composed of urate. Not ing of the native kidneys appears reasonable in all filling defects are stones. Blood clots, fungus patients undergoing US of a renal allograft. balls, or sloughed papillae are also encountered. Those Australian and New Zealand Dialysis and Transplant Registry patients who had Lymphoproliferative Disorder/Neoplasms renal transplantation as a result of analgesic nephropathy were found to be at an increased Renal transplant patients are immuno- risk of developing posttransplant transitional suppressed and, not surprisingly, are at an cell carcinomas of the upper urinary tracts com- increased risk of developing neoplasms. pared to patients undergoing transplantation Epstein-Barr virus infection is believed to be for other causes of renal failure (143); their responsible for most of this increased risk. To tumors tend to be of a higher grade and stage, put this issue in perspective, approximately 1% and they have a worse outcome than do other of renal transplant patients develop a lympho- transplant patients. Screening with urinalysis proliferative disorder, considerably more than and voided urine cytology does not appear to the general population. A retrospective Italian be reliable in detecting upper renal tract study found 15 cancers in 11 posttransplant malignancies. Annual cystoscopy and retro- patients, including skin cancers, Kaposi’s sarco- grade ureteral catheterization with washings, mas, renal carcinomas, transitional cell carci- brushings, and radiologic imaging were advo- noma, and even colon cancer (141); the mean cated in these patients. The patients should also time of immunosuppression until tumor detec- be screened before transplantation. tion was 45 months, and, surprisingly, no lym- Both bladder nephrogenic metaplasia and phomas or female genital tract cancers were nephrogenic adenomas develop in these found. patients; these benign tumors, considered to be Over the years, the sites of lymphoproli- without malignant potential, have a relatively ferative disorder involvement in renal trans- high relapse rate. Their long-term course in 674

ADVANCED IMAGING OF THE ABDOMEN these immunosuppressed patients is not Some of these patients develop acute rejection clear. and undergo steroid therapy. Also, a normal The prevalence of cutaneous squamous cell graft function does not exclude tuberculous carcinoma, basal cell carcinoma, cutaneous infection. malignant fibrous histiocytoma, atypical fibrox- anthoma, and Kaposi’s sarcoma is increased considerably over a control population. Among Failed Transplant other tumors, basal cell epithelioma of the scalp, Failed renal allografts are usually left in situ and gastric adenocarcinoma,central nervous system the patient then undergoes either dialysis or lymphoma, breast carcinoma, and adenocarci- retransplantation. Most of these failed kidneys noma of the colon have been reported. are asymptomatic and gradually shrink in size, An annual abdominal US appears to have a and a number eventually calcify. Some develop role in detecting some neoplasms in asympto- fatty infiltration and become hydronephrotic, matic renal allograft recipients. One should findings detectable with imaging.Acute enlarge- keep in mind, however, that US does not detect ment of a failed transplant should suggest an smaller tumors. Some evidence suggests that infarct and hemorrhage. MR is superior in detecting lymphoproliferative disorders. Lymphomas appear as soft tissue tumors isodense to soft tissue on CT and hypo- Other Complications dense postcontrast, iso- or hypoechoic with US, Torsion of an intraperitoneal renal transplant and hypo- to isointense on T1- and hypointense should be suspected if abnormal perfusion is on T2-weighted MRI and show minimal con- associated with a change in renal axis. trast enhancement. They are located in either Occasionally acute tubular necrosis develops renal parenchyma or renal hilum; at the in a newly transplanted allograft kidney follow- latter location encasement of hilar vessels ing unrelated surgery; Tc-99m-MAG3 scintigra- or excretory tract compression and obstruc- phy detects focal acute tubular necrosis. tion is common. In the absence of therapy, Not all pain in these patients is related to a calcifications suggest necrosis. transplant; right lower quadrant pain in renal transplant patients can be secondary to acute Infection appendicitis and related conditions. Bacterial allograft pyelonephritis leads to acute renal failure. Some patients also have superim- Post–Bone Marrow Transplant posed acute rejection. Viral infections, such as with cytomegalovirus, are also associated with Acute renal failure developed in roughly 25% of rejection. Therefore, in these patients both bone marrow transplant patients, most often imaging and graft biopsy are necessary. A rela- occurring during the first month after trans- tionship between urinary tract infection and plantation. This complication occurs primarily chronic rejection has been raised. in allogenic bone marrow transplantation. The Especially in children, vesicoureteral reflux is etiologies for such failure tend to be multifacto- a risk factor for pyelonephritis and graft dys- rial and include nephrotoxicity, liver veno- function. Comparing voiding cystourethrogra- occlusive disease, and others. phy and contrast enhanced voiding US in adults with transplanted kidneys and suspected of Nephrectomy reflux, US sensitivity and specificity for detect- ing reflux were 93% and 95%, respectively (144); An arteriovenous fistula of the renal pedicle is agreement between the two studies was 95%.An a rare complication of nephrectomy, at times antireflux reimplantation procedure is helpful developing years after a nephrectomy.Turbulent in some of these children. blood flow in the fistula often results in a bruit. Tuberculous nephropathy is uncommon in With time,the artery feeding a fistula and drain- renal transplant patients, even if they have ing vein dilate and collateral vessels develop. had chest tuberculosis preoperatively (145). Doppler US should detect these fistulas. 675

KIDNEYS AND URETERS

Conduits An arteriovenous fistula is probably more common than suspected after a renal biopsy. An ileal conduit is formed after a cystectomy. A Fistulas also develop secondary to renal surgery. not uncommon complication is an ureteroileal Some fistulas manifest with hematuria (Fig. stricture. These strictures are amenable to dila- 10.41), but many patients are asymptomatic. A tion with a balloon catheter, followed by stent- rare fistula leads to renal ischemia or even ing with a double-J stent, with good results. hypertension. Some are associated with a Stents can be inserted through urinary diver- pseudoaneurysm. sion stomas. Color Doppler US readily detects these Major ureteroileal reflux of a Kock pouch is fistulas and is useful in follow-up. Eventually, an occasional complication, and these patients most fistulas tend to resolve. If needed, a fistula undergo an antireflux ureteroileal implantation. is treated by superselective angiographic Follow-up of these patients is with a retrograde embolization, including transcatheter coil study to detect any reflux. occlusion. Usually such embolization results in An adenocarcinoma within an ileal conduit limited renal parenchymal loss. Postocclusion is a recognized but rare complication years hypertension is uncommon. later. If necessary, a ureteral defect is replaced by Catheter and Stent Related an interposed ileal loop (ureteroileoplasty), thus preserving ureter continuity. Several studies Minor complications of ureteral catheters and suggest that such ileal interposition is a safe and stents include hematuria, dysuria, frequency, effective procedure. and flank and suprapubic pain. Major compli- Some of the complications encountered cations encountered are initial catheter malpo- after ureterosigmoidostomy are pyelonephritis, sition, obstruction, stent migration or fracture, hyperchloremic metabolic acidosis, inconti- necrosis, erosion into adjacent structures, nence, and a late development of anastomotic and ureterovascular fistula. Some stents break colon carcinoma. spontaneously; others are associated with stone A patient with a ureterocutaneostomy devel- formation. A broken stent usually can be oped a squamous cell carcinoma at the stomal removed either by ureteroscopy or by using a site; presumably chronic infection and irritation percutaneous approach.An uncommon compli- of the indwelling catheter were factors in carci- cation is a knot forming in a ureteral catheter. A noma formation. stiff guidewire advanced through the catheter lumen aids in untying such a knot. Rarer com- plications include a pelvic abscess and even Examination and Surgical septic hip arthritis. Blood clots and debris can Complications obstruct the lumen, although flow is often both inside and around a stent. The risk of obstruc- Biopsy tion is decreased by using a large-bore catheter. Being foreign bodies, they lead to urinary Needle tract seeding after percutaneous biopsy infection and encrustation (Fig. 10.42). Encrus- occurs with numerous neoplasms, including tation is minimized by high fluid intake, treat- even a Wilms’ tumor, and some investigators do ing infections vigorously, and routine catheter not perform pretreatment needle biopsies of exchange. Both proximal and distal J-loops renal tumors in children for fear of needle tract minimize but do not prevent stent migration tumor seeding. either proximally or distally. Because stents are More hemorrhage, arteriovenous and arteri- radiopaque, their position is generally verified ocaliceal fistulas, and other complications are with conventional radiography. Computed encountered when renal biopsy is performed tomography establishes catheter patency indi- with a 14-gauge needle rather than when an 18- rectly by revealing an interval decrease in gauge needle is used. Also, percutaneous renal hydronephrosis. If necessary, a voiding cys- biopsy can lead to a subcapsular hematoma and togram establishes patency because most hypertension. catheters will reflux. Other tests of catheter 676

ADVANCED IMAGING OF THE ABDOMEN

A B

Figure 10.41. Hematuria after renal biopsy led to an arteriogram.Early (A) and late (B) arterial phase renal arteriograms reveal con- trast extravasation (arrow). Early venous filling was evident on other films. He underwent successful Gelfoam and Ivalon emboliza- tion. (Courtesy of Oscar Gutierrez, M.D., University of Chile, Santiago, Chile.)

A B

Figure 10.42. Ureteral stent encrustation. A: A conventional radiograph shows a right ureteral stent with radiopaque encrustation both proximally and distally. B: A urogram reveals ureteropelvic obstruction due to the proximal encrustation. Several cystoscopic attempts were necessary to treat the vesical encrustations. Renal encrustations were treat percutaneously and eventually the stent was successfully removed. (Source: Dyer RB, Chen MY, Zagoria RJ, Regan JD, Hood CG, Kavanagh PV. Complications of ureteral stent placement. RadioGraphics 2002;22:1005–1022, with permission from the Radiological Society of North America.) 677

KIDNEYS AND URETERS patency include Doppler US detection of Nephrostomy urinary jets and measurement of the resistance index with Doppler US. Nuclear renography, The most common indication for percutaneous often combined with a diuretic agent, evaluates nephrostomy is renal collecting system obstruc- patency in an appropriate clinical setting. tion; an occasional nephrostomy is performed Because urethral catheters positioned with a to bypass a ureteral fistula. These common distal tip in the bladder result in reflux, their procedures are associated with few serious use is inappropriate if additional reflux is complications. Transient hematuria is common detrimental. after the procedure. Occasional hemorrh- Stent erosion into an adjacent vessel is age requires transfusion. Rare complications favored by ischemia—often due to either prior include gallbladder puncture and peritonitis radiation therapy or extensive surgery. and air embolism. Most ureteral stents are retrieved cystoscopi- While palliative percutaneous nephrostomy cally. Occasionally it is necessary to retrieve does decompress a more distal malignant a stent using a percutaneous fluoroscopic obstruction, whether it improves quality of life approach. Some stents remain in place for a in patients with an unresectable cancer is number of years and become encrusted. The another question. initial approach to such a chronic stent should be an IV urogram to evaluate renal function and identify any obstruction. With no significant Related to Other Abdominopelvic encrustation, stent extraction under fluoro- Surgery scopic control is generally successful. With encrustation, ESWL can be successful. With a One complication of gynecologic surgery is fixed proximal J-curved stent percutaneous iatrogenic ureteral injury. The risk of ureteral removal may be successful. injury is about 10 times greater during an abdominal hysterectomy than during vaginal surgery; some of these injuries are relatively Vascular Complications asymptomatic and lead to a silent kidney loss. Significant hematuria occasionally develops A rare complication is a bladder or ureteroac- after an invasive percutaneous renal procedure. etabular fistula, often a result of extensive pelvic Angiography should detect any underlying surgery. vascular injury and, if necessary, transarterial An occasional surgical scar shows uptake of embolization with Gelfoam, steel coils, or other Tc-99m–methylene diphosphonate (MDP). material performed. A rare complication of renal angioplasty is acute pulmonary edema. Ureteroscopy Possible complications of ureteroscopic calculi removal are perforation, stricture, and even Nephrectomy ureter avulsion. Avulsion of the lumbar ureter Either a transabdominal or retroperitoneal is related to both ureteroscope and Dormia approach is used during laparoscopic radical catheter manipulation. During an iatrogenic nephrectomy. The incidence of complications ureteral perforation a calculus can be pushed and the need for conversion to open surgery into the retroperitoneum alongside the ureter. decreases with experience. These complications Such paraureteral calculi should not result in a range from access site complications, such as subsequent stricture. hernia formation and hematoma, to vascular injury, splenic laceration, adrenal injury, and Contrast Nephropathy pneumothorax. Computed tomography reliably identifies According to the Contrast Media Safety Com- postoperative bleeding, urinary leak, or ob- mittee of The European Society of Urogenital struction in these patients. Radiology, hemodialysis and peritoneal dialysis 678

ADVANCED IMAGING OF THE ABDOMEN remove both iodinated and gadolinium contrast agents are not completely innocuous, and occa- agents (146); several hemodialysis sessions or sional reports describe acute renal failure after several weeks of continuous ambulatory dialy- their use. Several reports describe use of sis are necessary to removal all contrast. It gadolinium-based contrast agents for CT should be noted, however, that hemodialysis imaging in patients with renal insufficiency or does not protect poorly functioning kidneys prior severe reaction to an iodinated agent. In against contrast induced nephrotoxicity. fact, the toxicity of gadolinium agents, at doses Contrast-associated nephropathy is a poorly achieving equivalent x-ray stopping power, is understood and generally unpredictable phe- greater than that of nonionic iodinated agents. nomenon. Its prevalence is increased in patients This is in distinction to the use of approved with diabetic nephropathy.Also, elderly patients lower gadolinium doses during MRI, which are and those who are azotemic,hypertensive,dehy- insufficient for useful x-ray contrast, and which drated, or have hyperuricemia are at increased have negligible nephrotoxicity. The European risk of developing contrast nephropathy. High Society of Urogenital Radiology position is that blood urea nitrogen and high creatinine levels gadolinium-based contrast agents are more are additional risk factors. nephrotoxic than iodinated contrast agents in Creatinine clearance is generally employed to equivalent x-ray attenuation doses and use of monitor changes in renal function due to sus- gadolinium contrast agents for angiography or pected contrast nephropathy, although the CT is not recommended. primary effect of contrast agents is on renal tubules rather than glomerular function. In either case, most changes are mild and References reversible and do not need therapy. Occasionally prolonged renal cortical con- 1. Tippins RB, Torres WE, Baumgartner BR, Baumgarten trast retention is evident after vascular contrast DA. Are screening serum creatinine levels necessary injection. While retention can be seen in such prior to outpatient CT examinations? Radiology conditions as hypotension, in some patients 2000;216:481–484. retention persists for several days or even lon- 2. Nemeth AJ, Patel SK. Pyelovenous backflow seen on CT urography. AJR 2004;182:532–533. ger in the absence of any known underlying 3. Nolte-Ernsting CC, Wildberger JE, Borchers H, abnormality. Computed tomography performed Schmitz-Rode T, Gunther RW. Multi-slice CT uro- hours after angiography identifies renal cortical graphy after diuretic injection: initial results. Rofo contrast in a minority of patients; these patients Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 2001;173:176–180. are at an increased risk, albeit low, of contrast- 4. Teh HS, Ang ES, Wong WC, et al. MR renography using associated nephropathy. The large contrast a dynamic gradient-echo sequence and low-dose volumes used correlate with contrast retention gadopentetate dimeglumine as an alternative to and nephropathy. radionuclide renography. AJR 2003;181:441–450. Hydration prior to contrast injection is effec- 5. Gehl HB, Lorch H, Amblank OB, Engerhoff B, Weiss HD. [Comparative magnetic resonance imaging of tive in decreasing the risk of contrast nephropa- renal space-occupying lesions with a high and low field thy. The use of low osmolar contrast agents also MRI system.] [German] Rofo Fortschr Geb Rontgenstr lessens the prevalence of contrast nephropathy. Neuen Bildgeb Verfahr 1998;169:484–489. Preliminary results suggest that prophylactic 6. Donnelly LF,Nelson RC. Renal excretion of gadolinium mimicking calculi on non-contrast CT. Pediatr Radiol prostaglandin E1 may have a role in patients at 1998;28:417. risk. 7. Obuchi M, Takahara T,Takahashi M, et al. [Breath-hold A neutral gadolinium chelate (gadobutrol), 3D MR urography with 2ml Gd-DTPA injection.] injected IV at doses of either 0.1 or 0.3mmol per [Japanese] Nippon Igaku Hoshasen Gakkai Zasshi kg of body weight in patients with margi- 1998;58:163–165. 8. Borthne AS, Pierre-Jerome C, Gjesdal KI, Storaas T, nal excretory function (creatinine clearance Courivaud F, Eriksen M. Pediatric excretory MR urog- <30mL/min), did not affect renal function and raphy: comparative study of enhanced and non- thus appears to be a safe MR contrast agent even enhanced techniques. Eur Radiol 2003;13:1423–1427. in patients with impaired renal function (147); 9. Allkemper T, Tombach B, Heindel W. [Gd-BOPTA enhanced excretory MR urography without adminis- hydration, treatment with diuretics, and tration of diuretics.] [German] Rofo Fortschr Geb hemodialysis are not required after the use of Rontgenstr Neuen Bildgeb Verfahr 2001;173:115– this contrast agent. Yet gadolinium contrast 120. 679

KIDNEYS AND URETERS

10. Neri E, Boraschi P, Caramella D, et al. Magnetic reso- 26. Moore EE, Cogbill TH, Malangoni MA, et al. Organ nance virtual endoscopy of the upper urinary tract. injury scaling. [Review] Surg Clin North Am 1995; AJR 2000;175:1697–1702. 75:293–303. 11. Rybicki FJ, Shu KM, Cibas ES, Fielding JR, 27. Dacher JN, Avni F, Francois A, et al. Renal sinus hyper- vanSonnenberg E, Silverman SG. Percutaneous biopsy echogenicity in acute pyelonephritis: description and of renal masses: sensitivity and negative predictive pathological correlation. Pediatr Radiol 1999;29:179– value stratified by clinical setting and size of masses. 182. AJR 2003;180:1281–1287. 28. Laguna R, Silva F, Orduna E, Conway JJ, Weiss S, 12. Preda A,Van Dijk LC,Van Oostaijen JA,Pattynama PM. Calderon C. Technetium-99m-MAG3 in early identi- Complication rate and diagnostic yield of 515 consec- fication of pyelonephritis in children. J Nucl Med 1998; utive ultrasound-guided biopsies of renal allografts 39:1254–1257. and native kidneys using a 14-gauge Biopty gun. Eur 29. Lonergan GJ, Pennington DJ, Morrison JC, Haws RM, Radiol 2003;13:527–530. Grimley MS, Kao TC. Childhood pyelonephritis: com- 13. Cluzel P, Martinez F, Bellin MF, et al. Transjugular parison of gadolinium-enhanced MR imaging and versus percutaneous renal biopsy for the diagnosis renal cortical scintigraphy for diagnosis. Radiology of parenchymal disease: comparison of sampling 1998;207:377–384. effectiveness and complications. Radiology 2000;215: 30. Kuo YT, Chen MT, Liu GC, Huang CN, Huang CL, 689–693. Huang CH. Emphysematous pyelonephritis: imaging 14. Hogan MJ, Coley BD, Jayanthi VR, Shiels WE, Koff SA. diagnosis and follow-up. Kao-Hsiung I Chih 1999;15: Percutaneous nephrostomy in children and adoles- 159–170. cents: outpatient management. Radiology 2001;218: 31. el Fakir Y, Kabbaj N, Dafiri R, Imani F. [Imaging 207–210. of urinary Candida bezoars.] [French] Prog Urol 15. Patel U, Hussain FF. Percutaneous nephrostomy of 1999;9:513–517. nondilated renal collecting systems with fluoroscopic 32. el Khader K, Lrhorfi MH, el Fassi J, Tazi K, Hachimi M, guidance: technique and results. Radiology 2004;233: Lakrissa A. [Urogenital tuberculosis. Experience in 10 226–233. years.] [French] Prog Urol 2001;11:62–67. 16. Caire JT, Ramus RM, Magee KP, Fullington BK, Ewalt 33. Kirchner TH, Kirchner J, Jacobi V.[Renal parenchymal DH, Twickler DM. MRI of fetal genitourinary anom- defects as signs of renal tuberculosis.] [German] Ront- alies. AJR 2003;181:1381–1385. genpraxis 2000;52:332–234. 17. Choi JY,Kim SH, Kim SH. Double-blind ureteral dupli- 34. Yagi S, Goto T, Kawamoto K, et al. Endoscopic treat- cation: report of two cases. Eur Radiol 2002;12 Suppl ment of refractory filarial chyluria: a preliminary 3:S136–139. report. J Urol 1998;159:1615–1618. 18. Wikstrom M, Hauger W, Sinagowitz E. [A triple ureter 35. Weber MA, Wasser K, Schwenger V, Hallscheidt P, with an ectopic opening into the vagina.] [Review] Nahm AM, Delorme S. [Palpable resistance in the right [German] Rofo Fortschr Geb Rontgenstr Neuen renal area. Xanthogranulomatous pyelonephritis with Bildgeb Verfahr 1999;171:497–498. fistulization in the colon ascendens and M. psoas 19. Zerin JM, Leiser J. The impact of vesicoureteral reflux major.] [German] Radiologe 2002;42:46–50. on contralateral renal length in infants with multi- 36. Leluc O, Andre M, Marciano S, Lafforgue P, Rossi D, cystic dysplastic kidney. Pediatr Radiol 1998;28:683– Bartoli J. [Retroperitoneal complications of Erdheim- 686. Chester disease.] [French] J Radiol 2001;82:580–582. 20. Feather SA, Winyard PJ, Dodd S, Woolf AS. Oral- 37. Schmidt T, Hohl C, Haage P, et al. Diagnostic accuracy facial-digital syndrome type 1 is another dominant of phase-inversion tissue harmonic imaging versus polycystic kidney disease: clinical, radiological and fundamental B-mode sonography in the evaluation of histopathological features of a new kindred. Nephrol focal lesions of the kidney. AJR 2003;180:1639–1647. Dial Transplant 1997;12:1354–1361. 38. Tello R, Davison BD, O’Malley M, et al. Magnetic reso- 21. Hateboer N, v Dijk MA, Bogdanova N, et al. Compari- nance imaging of renal masses interpreted on CT to be son of phenotypes of polycystic kidney disease types suspicious. AJR 2000;174:1017–1022. 1 and 2. European PKD1–PKD2 Study Group. Lancet 39. Bain ES, Kinney TB, Gooding JM, Casola G,Ysrael MZ. 1999;353:103–107. Sinus histiocytosis with massive lymphadenopathy 22. Nicolau C, Torra R, Badenas C, et al. Autosomal domi- (Rosai-Dorfman disease): a rare cause of bilateral renal nant polycystic kidney disease types 1 and 2: assess- masses. AJR 1999;172:995–996. ment of US sensitivity for diagnosis. Radiology 1999; 40. Townsend MF 3rd, Gal AA, Thoms WW, Newman JL, 213:273–276. Eble JN, Graham SD Jr. Ureteral rhabdomyosarcoma. 23. Neumann HP, Bender BU, Berger DP, et al. Prevalence, Urology 1999(online);54:561. morphology and biology of renal cell carcinoma in von 41. Johraku A, Miyanaga N, Sekido N, et al. A case Hippel-Lindau disease compared to sporadic renal cell of intravascular papillary endothelial hyperplasia carcinoma. J Urol 1998;160:1248–1254. (Masson’s tumor) arising from renal sinus. Jpn J Clin 24. Dondi M, Fanti S, Monetti N. Bartter’s syndrome: renal Oncol 1997;27:433–436. scintigraphic appearance after captopril administra- 42. Bosniak MA. The use of the Bosniak classification tion. J Nucl Med 1996;37:1688–1690. system for renal cysts and cystic tumors. J Urol 25. Forget S, Patriquin HB, Dubois J, et al. The kidney in 1997;157:1852–1853. children with tyrosinemia: sonographic, CT and 43. Curry NS, Cochran ST, Bissada NK. Cystic renal biochemical findings. Pediatr Radiol 1999;29:104– masses: accurate Bosniak classification requires ade- 108. quate renal CT. AJR 2000;175:339–342. 680

ADVANCED IMAGING OF THE ABDOMEN

44. Israel GM, Hindman N, Bosniak MA. Evaluation of with or without renal vein thrombosis.] [French] Prog cystic renal masses: comparison of CT and MR Urol 1999;9:649–654. imaging by using the Bosniak classification system. 61. Remer EM, Weinberg EJ, Oto A, O’Malley CM, Gill IS. Radiology 2004;231:365–371. Magnetic resonance imaging of the kidneys after 45. Chung EP, Herts BR, Linnell G, et al. Analysis of laparoscopic cryoablation. AJR 2000;174:635–640. changes in attenuation of proven renal cysts on differ- 62. Mayo-Smith WW, Dupuy DE, Parikh PM, Pezzullo JA, ent scanning phases of triphasic MDCT. AJR Cronan JJ. Imaging-guided percutaneous radiofre- 2004;182:405–410. quency ablation of solid renal masses: techniques and 46. Bae KT, Heiken JP, Siegel CL, Bennett HF. Renal outcomes of 38 treatment sessions in 32 consecutive cysts: is attenuation artifactually increased on con- patients. AJR 2003;180:1503–1508. trast-enhanced CT images? Radiology 2000;216:792– 63. Lewin JS, Nour SG, Connell CF, et al. Phase II clinical 796. trial of interactive MR imaging-guided interstitial 47. Macari M, Bosniak MA. Delayed CT to evaluate radiofrequency thermal ablation of primary kidney renal masses incidentally discovered at contrast- tumors: initial experience. Radiology 2004;232:835– enhanced CT: demonstration of vascularity with de- 845. enhancement. Radiology 1999;213:674–680. 64. McLaughlin CA, Chen MY, Torti FM, Hall MC, Zagoria 48. Slywotzky CM, Bosniak MA. Localized cystic disease of RJ. Radiofrequency ablation of isolated local recur- the kidney. AJR 2001;176:843–849. rence of renal cell carcinoma after radical nephrec- 49. Storkel S, van den Berg E. Morphological classification tomy. AJR 2003;181:93–94. of renal cancer. World J Urol 1995;13:153–158. 65. Hafez KS, Novick AC, Campbell SC. Patterns of tumor 50. Kovacs G,Akhtar M, Beckwith BJ, et al. The Heidelberg recurrence and guidelines for followup after nephron classification of renal cell tumours. [Review] J Pathol sparing surgery for sporadic renal cell carcinoma. 1997;83:131–133. J Urol 1997;157:2067–2070. 51. Kim JK, Kim TK, Ahn HJ, Kim CS, Kim KR, Cho KS. 66. Quaia E, Siracusano S, Bertolotto M, Monduzzi M, Differentiation of subtypes of renal cell carcinoma on Mucelli RP. Characterization of renal tumours with helical CT scans. AJR 2002;178:1499–1506. pulse inversion harmonic imaging by intermittent 52. Toro JR, Glenn G, Duray P, et al. Birt-Hogg-Dube syn- high mechanical index technique: initial results. Eur drome: a novel marker of kidney neoplasia. Arch Der- Radiol 2003;13:1402–1412. matol 1999;135:1195–1202. 67. Shishikura Y, Furusato M, Aizawa S. Cystic renal cell 53. Brauch H, Weirich G, Hornauer MA, Storkel S, Wohl T, carcinoma: arose as a simple cyst, recurred repeatedly Bruning T. Trichloroethylene exposure and specific as a multicystic mass and finally presented as a solid somatic mutations in patients with renal cell carci- mass. Pathol Int 1998;48:623–628. noma. J Nat Cancer Inst 1999;91:854–661. 68. Mahnken AH, Wildberger JE, Bergmann F, Fuzesi L, 54. Ligato S, Ro JY, Tamboli P,Amin MB, Ayala AG. Benign Adam G, Gunther R. [Papillary renal cell carcinoma: tumors and tumor-like lesions of the adult kidney. Part comparison of CT and gross morphology.] [German] I: Benign renal epithelial neoplasms. Adv Anat Pathol Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 1999;6:1–11. 2000;172:1011–1015. 55. Ascenti G, Gaeta M, Magno C, et al. Contrast-enhanced 69. Lesavre A,Correas JM,Merran S,Grenier N,Vieillefond second-harmonic sonography in the detection of A, Helenon O. CT of papillary renal cell carcinomas pseudocapsule in renal cell carcinoma. AJR 2004;182: with cholesterol necrosis mimicking angiomyolipo- 1525–1530. mas. AJR 2003;181:143–145. 56. Scialpi M, Di Maggio A, Midiri M, Loperfido A, 70. Sijmons RH, Kiemeney LA, Witjes JA, Vasen HF. Angelelli G,Rotondo A.Small renal masses: assessment Urinary tract cancer and hereditary nonpolyposis col- of lesion characterization and vascularity on dynamic orectal cancer: risks and screening options. J Urol contrast-enhanced MR imaging with fat suppression. 1998;160:466–470. AJR 2000;175:751–757. 71. Kitamura Y, Watanabe M, Komatsubara S, Sakata Y, 57. Yoshimitsu K, Honda H, Kuroiwa T, et al. Magnetic Miyajima N. [Regional lymph node metastasis in renal resonance detection of cytoplasmic fat in clear cell pelvic or ureteral cancer.] [Japanese] Nippon renal cell carcinoma utilizing chemical shift gradient- Hinyokika Gakkai Zasshi 1998;89:522–528. echo imaging. J Magn Reson Imaging 1999;9:579– 72. Van Glabeke E, Chartier-Kastler E, Delcourt A, 585. Cluzel P,Bruel S, Richard F. [Epidermoid cancer of the 58. Schubert RA, Schleicher C, Mentzel HJ, Wunderlich H, kidney pelvis.] [French] Prog Urol 2000;10:1200– Schubert J, Kaiser WA. [The observed and chance- 1203. corrected agreement of the computed tomographic 73. Rohrschneider WK, Weirich A, Rieden K, Darge K, and histological staging results in renal-cell carci- Troger J, Graf N. US, CT and MR imaging characteris- noma.] [German] Rofo Fortschr Geb Rontgenstr tics of nephroblastomatosis. Pediatr Radiol 1998;28: Neuen Bildgeb Verfahr 1999;170:358–364. 435–443. 59. Ergen FB, Hussain HK, Caoili EM, et al. MRI for 74. Kumar R, Fitzgerald R, Breatnach F. Conservative sur- preoperative staging of renal cell carcinoma us- gical management of bilateral Wilms tumor: results of ing the 1997 TNM classification: comparison with the United Kingdom Children’s Cancer Study Group. surgical and pathologic staging. AJR 2004;182:217– J Urol 1998;160:1450–1453. 225. 75. Jeanes AC, Beese RC, McHugh K, Ramsay AD. Fatty 60. Lebret T, Becette V, Colau A, et al. [Study of the Ki-67 degeneration in a Wilms’ tumour after chemotherapy. antibody immunolabeling of renal adenocarcinomas Eur Radiol 2002;12 Suppl 3:S149–151. 681

KIDNEYS AND URETERS

76. Isaac MA, Vijayalakshmi S, Madhu CS, Bosincu L, gadolinium-enhanced three-dimensional FLASH com- Nogales FF. Pure cystic nephroblastoma of the ovary pared with urography AJR 2001;176:105–112. with a review of extrarenal Wilms’ tumors. [Review] 93. Foda MM, Gatfield CT, Matzinger M, et al. A prospec- Hum Pathol 2000;31:761–764. tive randomized trial comparing 2 diuresis renography 77. Eble JN, Bonsib SM. Extensively cystic renal neo- techniques for evaluation of suspected upper urinary plasms: cystic nephroma, cystic partially differentiated tract obstruction in children. J Urol 1998;159:1691– nephroblastoma, multilocular cystic renal cell carci- 1693. noma, and cystic hamartoma of renal pelvis. [Review] 94. Harrington TG, Kandel LB. Renal colic following a Semin Diagn Pathol 1998;15:2–20. gunshot wound to the abdomen: the birdshot calculus. 78. Nagao T, Sugano I, Ishida Y, et al. Cystic partially J Urol 1997;157:1351–1352. differentiated nephroblastoma in an adult: an im- 95. Sheafor DH, Hertzberg BS, Freed KS, et al. Non- munohistochemical, lectin histochemical and ultra- enhanced helical CT and US in the emergency eval- structural study. Histopathology 1999;35:65–73. uation of patients with renal colic: prospective 79. Pages A, Granier M. [Nephronogenic nephroma com-parison. Radiology 2000;217:792–797. (author’s transl).] [French] Arch Anat Cytol Pathol 96. Assi Z, Platt JF, Francis IR, Cohan RH, Korobkin M. 1980;28:99–103. Sensitivity of CT scout radiography and abdominal 80. Renshaw AA, Freyer DR, Hammers YA. Metastatic radiography for revealing ureteral calculi on helical metanephric adenoma in a child. Am J Surg Pathol CT: implications for radiologic follow-up. AJR 2000;24:570–574. 2000;175:333–337. 81. Keshani de Silva V, Tobias V, Kainer G, Beckwith B. 97. Zagoria RJ, Khatod EG, Chen MY. Abdominal radiog- Metanephric adenoma with embryonal hyperplasia of raphy after CT reveals urinary calculi: a method to Bowman’s capsular epithelium: previously unreported predict usefulness of abdominal radiography on the association. Pediatr Dev Pathol 2000;3:472–478. basis of size and CT attenuation of calculi. AJR 82. Argani P, Beckwith JB. Metanephric stromal tumor: 2001;176:1117–1122. report of 31 cases of a distinctive pediatric renal neo- 98. Chong WK, Wysoki M, Heller LG, Zegel HG. Renal car- plasm. Am J Surg Pathol 2000;24:917–926. cinoma presenting with flank pain: a potential draw- 83. Sakhuja V, Jha V,Varma S, et al. Renal involvement in back of unenhanced CT. AJR 2000;174:667–669. multiple myeloma: a 10–year study. Ren Fail 2000;22: 99. Goldman SM, Faintuch S, Ajzen SA, et al. Diagnostic 465–477. value of attenuation measurements of the kidney on 84. Burdeny DA, Semelka RC, Kelekis NL, Reinhold C, unenhanced helical CT of obstructive ureterolithiasis. Ascher SM. Small (<1.5cm) angiomyolipomas of the AJR 2004;182:1251–1254. kidney: characterization by the combined use of in- 100. Jones RA, Perez-Brayfield MR, Kirsch AJ, Grattan- phase and fat-attenuated MR techniques. Magn Reson Smith JD. Renal transit time with MR urography in Imaging 1997;15:141–145. children. Radiology 2004;233:41–50. 85. Lee W, Kim TS, Chung JW, Han JK, Kim SH, Park JH. 101. Takahashi N, Kawashima A, Ernst RD, et al. Renal angiomyolipoma: embolotherapy with a mixture Ureterolithiasis: can clinical outcome be predicted of alcohol and iodized oil. J Vasc Interv Radiol 1998;9: with unenhanced helical CT? Radiology 1998;208: 255–261. 97–102. 86. Haddad FS, de la Vega DJ, DuBose Dent E Jr, Shippel 102. Frauscher F, Janetschek G, Helweg G, Strasser H, RM. Renal fibrohistiocytic sarcoma. Three cases and a Bartsch G, zur Nedden D. Crossing vessels at the review of the literature. [Review] J Med Liban 1998;46: ureteropelvic junction: detection with contrast- 335–342. enhanced color Doppler imaging. Radiology 1999;210: 87. Tsurukawa H, Iuchi H, Osanai H, et al. [Renomedullary 727–731. interstitial cell tumor: a case report.] [Review] 103. Nishie A,Yoshimitsu K, Irie H, et al. Radiologic features [Japanese] Nippon Hinyokika Gakkai Zasshi 2000;91: of Castleman’s disease occupying the renal sinus. AJR 37–40. 2003;181:1037–1040. 88. Tajima K, Saito K, Umeda Y,Murata T, Satani H. Malig- 104. Geavlete P, Georgescu D, Nita G, Cauni V. [Doppler nant melanoma of the kidney presenting as a primary ultrasonography in the function assessment of double tumor. Int J Urol 1997;4:94–96. J ureteral endoprosthesis in patients with extrinsic 89. Soulie M, Escourrou G, Vazzoler N, et al. [Primary car- ureteral obstruction.] [French] Prog Urol 2001;11: cinoid tumor and horseshoe kidney: potential associ- 22–28. ation.] [French] Prog Urol 2001;11:301–303. 105. Sugamoto T, Yokoyama M, Nishio S, Takeuchi M. 90. Georgiades CS, Moore CJ, Smith DP. Differences of Cholesteatoma of the ureter: a case report.[Review] Int renal parenchymal attenuation for acutely obstructed J Urol 1997;4:621–622. and unobstructed kidneys on unenhanced helical CT: 106. Weinberg B,Yeung N. Sonographic sign of intermittent a useful secondary sign? AJR 2001;76:965–968. dilatation of the renal collecting system in 10 patients 91. Garcia-Pena BM, Keller MS, Schwartz DS, Korsvik HE, with vesicoureteral reflux. J Clin Ultrasound 1998;26: Weiss RM. The ultrasonographic differentiation of 65–68. obstructive versus nonobstructive hydronephrosis 107. Darge K, Troeger J. Vesicoureteral reflux grading in in children: a multivariate scoring system. J Urol 1997; contrast-enhanced voiding urosonography. Eur J 158:560–565. Radiol 2002;43:122–128. 92. Sudah M, Vanninen R, Partanen K, Heino A, Vainio P, 108. Bertschy C, Aubert D, Piolat C, Billerey C. [Uretero- Ala-Opas M. Magnetic resonance urography in evalu- vesical implantation after failure of endoscopic treat- ation of acute flank pain: T2–weighted sequences and ment of reflux: anatomical and histological study of 61 682

ADVANCED IMAGING OF THE ABDOMEN

resection specimens from 40 children.] [French] Prog 126. Selcuk NY,Odabas AR, Cetinkaya R, Tonbul HZ, San A. Urol 2001;11:113–117. Outcome of pregnancies with HELLP syndrome com- 109. Olbing H, Hirche H, Koskimies O, et al. Renal growth plicated by acute renal failure (1989–1999). Ren Fail in children with severe vesicoureteral reflux: 10-year 2000;22:319–327. prospective study of medical and surgical treatment: 127. Angelelli G, Stabile Ianora AA, Scardapane A, the International Reflux Study in Children (European Rotondo A. [Computerized tomography in the study of branch).] Radiology 2000;216:731–737. the diabetic kidney.] [Italian] Radiol Med 2000;99:72– 110. Chow WH, Lindblad P,Gridley G, et al. Risk of urinary 80. tract cancers following kidney or ureter stones. J Nat 128. Johnston RJ, Alkhunaizi AM. Unilateral focal segmen- Cancer Inst 1997;89:1453–1457. tal glomerulosclerosis with contralateral sparing on 111. Daudon M. [Drug-induced urinary calculi in 1999.] the side of renal artery stenosis. AJR 1999;172:35– [Review] [French] Prog Urol 1999;9:1023–1033. 37. 112. Saw KC, McAteer JA, Monga AG, Chua GT, Lingeman 129. Colli A, Fraquelli M, Pometta R, Cocciolo M, Visentin JE, Williams JC Jr. Helical CT of urinary calculi: effect S, Conte D. Renovascular impedance and esophageal of stone composition, stone size, and scan collimation. varices in patients with Child-Pugh class A cirrhosis. AJR 2000;175:329–332. Radiology 2001;219:712–715. 113. Mostafavi MR, Ernst RD, Saltzman B. Accurate deter- 130. Katagiri K, Okada S, Kumazaki T, Tsuboi N. [Clearance mination of chemical composition of urinary calculi of gadolinium contrast agent by hemodialysis: in by spiral computerized tomography. J Urol 1998;159: vitro and clinical studies.] [Japanese] Nippon Igaku 673–675. Hoshasen Gakkai Zasshi 1998;58:739–744. 114. Lee JY, Kim SH, Cho JY, Han D. Color and power 131. Takebayashi S, Hidai H, Chiba T, Takagi H, Koike S, Doppler twinkling artifacts from urinary stones: clin- Matsubara S. Using helical CT to evaluate renal cell ical observations and phantom studies. AJR 2001;176: carcinoma in patients undergoing hemodialysis: 1441–1445. value of early enhanced images. AJR 1999;172:429– 115. Chelfouh N, Grenier N, Higueret D, et al. Characteriza- 433. tion of urinary calculi: in vitro study of “twinkling arti- 132. Vidart A, Pfister C, Bugel H, Savoye-Collet C, Thoumas fact” revealed by color-flow sonography. AJR 1998;171: D, Grise P. [Role of helical tomodensitometry in the 1055–1060. early diagnosis of renal infarction.] [French] Prog Urol 116. Dore B. [Management of renal calix calculosis.] 2001; 11:217–221. [Review] [French] Presse Med 1999;28:2181–2188. 133. Di Fiori JL, Rodrigue D, Kaptein EM, Ralls PW. Diag- 117. Soh J. [The maximum volume of urinary calculi to be nostic sonography of HIV-associated nephropathy: disintegrated by ESWL.] [Japanese] Nippon Hinyokika new observations and clinical correlation. AJR Gakkai Zasshi 1998;89:23–28. 1998;171:713–716. 118. Traxer O, Lottmann H, Archambaud F,Helal B, Mercier 134. Rankin SC, Jan W, Koffman CG. Noninvasive imaging Pageyral B. [Long-term evaluation with DMSA-Tc 99m of living related kidney donors: evaluation with CT scintigraphy of renal parenchymal involvement in angiography and gadolinium-enhanced MR angiogra- children after shockwave extracorporeal lithotripsy.] phy. AJR 2001;177:349–355. [French] Prog Urol 1998;8:502–506. 135. Fink C, Hallscheidt PJ, Hosch WP, et al. Preoperative 119. Chan KF,Vassar GJ, Pfefer TJ, et al. Holmium:YAG laser evaluation of living renal donors: value of contrast- lithotripsy: a dominant photothermal ablative mecha- enhanced 3D magnetic resonance angiography and nism with chemical decomposition of urinary calculi. comparison of three rendering algorithms. Eur Radiol Lasers Surg Med 1999;25:22–37. 2003;13:794–801. 120. Havel D, Saussine C, Fath C, Lang H, Faure F, Jacqmin 136. Jha RC, Korangy SJ, Ascher SM, Takahama J, Kuo PC, D. Single stones of the lower pole of the kidney. Johnson LB. MR angiography and preoperative evalu- Comparative results of extracorporeal shock wave ation for laparoscopic donor nephrectomy. AJR 2002; lithotripsy and percutaneous nephrolithotomy. Eur 178:1489–1495. Urol 1998;33:396–400. 137. Moresco KP,Patel NH,Namyslowski Y,Shah H,Johnson 121. Gremmo E, Ballanger P, Dore B, Aubert J. [Hemor- MS, Trerotola SO. Carbon dioxide angiography of the rhagic complications during percutaneous transplanted kidney: technical considerations and nephrolithotomy. Retrospective studies of 772 cases.] imaging findings. AJR 1998;171:1271–1276. [French] Prog Urol 1999;9:460–463. 138. Hilborn MD, Bude RO, Murphy KJ, Platt JF, Rubin JM. 122. Schillinger F, Delclaux B, Milcent T, et al. [Renal sar- Renal transplant evaluation with power Doppler coidosis with a pseudotumoral pyelic localization.] sonography. Br J Radiol 1997;70:39–42. [French] Presse Med 1999;28:683–685. 139. Amodio F, Rossi E, Carbone M, et al. [Echographic 123. Yassa NA, Peng M, Ralls PW. Perirenal lucency study with high-frequency and high-spatial resolution (“kidney sweat”): a new sign of renal failure. AJR transducer in the evaluation of renal transplant in 1999;173:1075–1077. pediatric age.] [Italian] Radiol Med 2000;99:68–71. 124. Delzell E, Shapiro S. A review of epidemiologic studies 140. Heindel W, Kugel H, Wenzel F, Stippel D, Schmidt R, of nonnarcotic analgesics and chronic renal disease. Lackner K. Localized 31P MR spectroscopy of the [Review] Medicine 1998;77:102–121. transplanted human kidney in situ shows altered 125. Michail S, Stathakis C, Nakopoulou L, et al. Acute renal metabolism in rejection and acute tubular necrosis. failure in an adult patient with Henoch-Schoenlein J Magn Reson Imaging 1997;7:858–864. purpura after episode of macroscopic hematuria. Ren 141. Capocasale E, Bignardi L, Adorni A, D’Errico G, Viola Fail 1999;21:107–111. V, Botta GC. [Neoplasms and kidney transplantation. 683

KIDNEYS AND URETERS

Case contribution.] [Italian] Minerva Urol Nefrol adult patients prior to antireflux ureteral implantation. 1998;50:127–131. Radiology 2004;233:35–39. 142. Lopez-Ben R, Smith JK, Kew CE 2nd, Kenney PJ, Julian 145. Lezaic V, Radivojevic R, Radosavljevic G, et al. Does BA, Robbin ML. Focal posttransplantation lymphopro- tuberculosis after kidney transplantation follow the liferative disorder at the renal allograft hilum. AJR trend of tuberculosis in general population? Ren Fail 2000;175:1417–1422. 2001;23:97–106. 143. Swindle P,Falk M, Rigby R, Petrie J, Hawley C, Nicol D. 146. Morcos SK, Thomsen HS, Webb JA, et al. Dialysis and Transitional cell carcinoma in renal transplant recipi- contrast media. Eur Radiol 2002;12:3026–3030. ents: the influence of compound analgesics. Br J Urol 147. Tombach B, Bremer C, Reimer P, et al. Renal tolerance 1998;81:229–233. of a neutral gadolinium chelate (gadobutrol) in 144. Valentini AL, De Gaetano AM, Minordi LM, et al. patients with chronic renal failure: results of a ran- Contrast-enhanced voiding US for grading of reflux in domized study. Radiology 2001;218:651–657.