Chapter 540 ◆ Obstruction of the Urinary Tract 2567

Table 540-1 Types and Causes of Urinary Tract Obstruction

LOCATION CAUSE Infundibula Congenital Calculi Inflammatory (tuberculosis) Traumatic Postsurgical Neoplastic Congenital (infundibulopelvic ) Inflammatory (tuberculosis) Calculi Neoplasia (Wilms tumor, neuroblastoma) Ureteropelvic junction Congenital stenosis Chapter 540 Calculi Neoplasia Inflammatory Obstruction of the Postsurgical Traumatic Congenital obstructive Urinary Tract Midureteral structure Jack S. Elder Ureteral ectopia Retrocaval ureter Ureteral fibroepithelial polyps Most childhood obstructive lesions are congenital, although urinary Ureteral valves tract obstruction can be caused by trauma, neoplasia, calculi, inflam- Calculi matory processes, or surgical procedures. Obstructive lesions occur at Postsurgical any level from the urethral meatus to the calyceal infundibula (Table Extrinsic compression 540-1). The pathophysiologic effects of obstruction depend on its level, Neoplasia (neuroblastoma, lymphoma, and other retroperitoneal or pelvic the extent of involvement, the child’s age at onset, and whether it is tumors) acute or chronic. Inflammatory (Crohn , chronic granulomatous disease) ETIOLOGY Hematoma, urinoma Ureteral obstruction occurring early in fetal life results in renal dys- Lymphocele plasia, ranging from multicystic , which is associated with ure- teral or pelvic atresia (see Fig. 537-2 in Chapter 537), to various Bladder outlet and Neurogenic bladder dysfunction degrees of histologic renal cortical dysplasia that are seen with less- (functional obstruction) severe obstruction. Chronic ureteral obstruction in late fetal life or Posterior urethral valves after birth results in dilation of the ureter, renal pelvis, and calyces, Anterior urethral valves with alterations of renal parenchyma ranging from minimal tubular Diverticula changes to dilation of Bowman’s space, glomerular fibrosis, and inter- Urethral strictures (congenital, traumatic, stitial fibrosis. After birth, often complicate obstruction and or iatrogenic) can increase renal damage. Urethral atresia Ectopic ureterocele Prenatal screening with ultrasonography may detect antenatal (males) , which is graded by the trimester and the anterior- Calculi posterior diameter of the renal pelvis (Table 540-2); most are mild. Foreign bodies Table 540-3 notes the eventual etiology. Phimosis Extrinsic compression by tumors CLINICAL MANIFESTATIONS anomalies Obstruction of the urinary tract generally causes hydronephrosis, which typically is asymptomatic in its early phases. An obstructed kidney secondary to a ureteropelvic junction (UPJ) or ureterovesical junction obstruction can manifest as a unilateral mass or cause upper abdominal or flank pain on the affected side. can occur because of urinary stasis. An upper urinary tract stone can occur, Table 540-2 Definition of Antenatal Hydronephrosis by causing abdominal and flank pain and . With bladder outlet Anterior-Posterior Diameter obstruction, the urinary stream may be weak; urinary tract (UTI; see Chapter 538) is common. Many of these lesions are identified DEGREE OF by antenatal ultrasonography; an abnormality involving the genitouri- ANTENATAL SECOND THIRD nary tract is suspected in as many as 1 in 100 . HYDRONEPHROSIS TRIMESTER TRIMESTER Obstructive renal insufficiency can manifest itself by failure to Mild 4 to <7 mm 7 to <9 mm thrive, vomiting, diarrhea, or other nonspecific . Moderate 7 to ≤10 mm 9 to ≤15 mm In older children, infravesical obstruction can be associated with over- flow or a poor stream. Acute ureteral Severe >10 mm >15 mm obstruction causes flank or ; there may be and From Nguyen HT, Herndon CDA, Cooper C, et al: The society for fetal . Chronic ureteral obstruction can be silent or can cause vague consensus statement on the evaluation and management of antenatal abdominal or typical flank pain with increased fluid intake. hydronephrosis. J Pediatr Urol 6:212–231, 2010, Table 2, p. 215. Part XXIV ◆ Urologic Disorders in Infants and Children 2568

parenchymal thickness, and presence or absence of ureteral dilation DIAGNOSIS should be assessed. Most pediatric urologists grade the severity of Urinary tract obstruction may be diagnosed prenatally by ultrasonog- hydronephrosis from 1-4 using the Society for Fetal Urology grading raphy, which typically shows hydronephrosis and occasionally a dis- scale (Table 540-4), whereas pediatric radiologists generally utilize the tended bladder. More complete evaluation, including imaging studies, adjectives mild, moderate, and severe. The clinician should ascertain should be undertaken in these children in the neonatal period. that the contralateral kidney is normal, and the bladder should be Urinary tract obstruction is often silent. In the newborn infant, a imaged to see whether the bladder wall is thickened, the lower ureter palpable abdominal mass most commonly is a hydronephrotic or mul- is dilated, and bladder emptying is complete. In acute or intermittent ticystic dysplastic kidney. With posterior urethral valves, which is an obstruction, the dilation of the collecting system may be minimal and infravesical obstructive lesion in boys, a walnut-sized mass represent- ultrasonography may be misleading. ing the bladder is palpable just above the pubic symphysis. A patent draining also can suggest urethral obstruction. Urinary Voiding Cystourethrogram ascites in the newborn usually is caused by renal or bladder urinary In neonates and infants with congenital grade 3 or 4 hydronephrosis extravasation secondary to posterior urethral valves. Infection and and in any child with ureteral dilation, a contrast voiding cystoure- may be the first indications of an obstructive lesion of the throgram (VCUG) should be obtained, because the dilation is second- urinary tract. The combination of infection and obstruction poses a ary to in 15% of cases. In boys, the VCUG also is serious threat to infants and children and generally requires parenteral performed to rule out urethral obstruction, particularly in cases of administration of and drainage of the obstructed kidney. suspected posterior urethral valves. In older children, the urinary flow should be performed in all children during the rate can be measured noninvasively with a urinary flowmeter; decreased acute stage of an initial febrile UTI. flow with a normal bladder contraction suggests infravesical obstruc- tion (e.g., posterior urethral valves, ). When the Imaging Studies urethra cannot be catheterized to obtain a VCUG, the clinician should Renal Ultrasonography suspect a urethral stricture or an obstructive urethral lesion. Retro- Hydronephrosis is the most common characteristic of obstruction grade urethrography with contrast medium injected into the urethral (Fig. 540-1). Upper urinary tract dilation is not diagnostic of obstruc- meatus helps delineate the anatomy of the urethral obstruction. tion and often persists after surgical correction of a significant obstruc- tive lesion. Dilation can result from vesicoureteral reflux, or it may be Radioisotope Studies a manifestation of abnormal development of the urinary tract, even Renal is used to assess renal anatomy and function. The when there is no obstruction. Renal length, degree of caliectasis and 2 most commonly used radiopharmaceuticals are mercaptoacetyl tri- glycine (MAG-3) and technetium-99m-labeled dimercaptosuccinic acid. MAG-3, which is excreted by renal tubular secretion, is used to Table 540-3 The Etiology of Antenatal Hydronephrosis assess differential renal function, and when furosemide is adminis- tered, drainage also can be measured. An alternative to MAG-3 is ETIOLOGY INCIDENCE diethylene tetrapentaacetic acid, which is cleared by glomerular filtra- Transient hydronephrosis 41-88% tion. The background activity of diethylene tetrapentaacetic acid is much higher than that of MAG-3. Dimercaptosuccinic acid is a renal Ureteropelvic junction obstruction 10-30% cortical imaging agent and is used to assess differential renal function Vesicoureteral reflux 10-20% and to demonstrate whether renal scarring is present. It is used infre- Ureterovesical junction obstruction/megaureters 5-10% quently in children with . In a MAG-3 renogram, a small dose of technetium-labeled Multicystic dysplastic kidney 4-6% MAG-3 is injected intravenously (Figs. 540-2 and 540-3). During the /urethral atresia 1-2% 1st 2-3 min, renal parenchymal uptake is analyzed and compared, allowing computation of differential renal function. Subsequently, Ureterocele//duplex system 5-7% Others: , cystic , Uncommon congenital ureteric strictures, and megalourethra Table 540-4 Society for Fetal Urology Grading System From Nguyen HT, Herndon CDA, Cooper C, et al: The society for fetal urology for Hydronephrosis consensus statement on the evaluation and management of antenatal hydronephrosis. J Pediatr Urol 6:212–231, 2010, Table 5, p. 217. Renal Image RENAL GRADE OF CENTRAL RENAL PARENCHYMAL HYDRONEPHROSIS COMPLEX THICKNESS 0 Intact Normal 1 Slight splitting Normal 2 Evident splitting, Normal complex confined within renal border 3 Wide splitting pelvis Normal dilated outside renal border, calyces uniformly dilated 4 Further dilation of pelvis Thin and calyces (calyces may appear convex)

Figure 540-1 Ultrasonographic image of the kidney with marked After Maizels M, Mitchell B, Kass E, et al: Outcome of nonspecific pelvic and calyceal dilation (grade 4 hydronephrosis) in a newborn with hydronephrosis in the infant: a report from the registry of the Society for Fetal ureteropelvic junction obstruction. Urology, J Urol 152:2324–2327, 1994. Chapter 540 ◆ Obstruction of the Urinary Tract 2569

Function cts/sec

A B Time (min) Figure 540-2 Same patient as in Figure 540-1. MAG-3 diuretic renogram of a 6 wk old patient. The right kidney is on the right side of the image. A, Differential renal function: left kidney 70%, right kidney 30%. B, After administration of furosemide, drainage from the left kidney was normal and drainage from the right kidney was slow, consistent with right ureteropelvic junction obstruction. Pyeloplasty was performed on the right kidney.

Function cts/sec

A B Time (min) Figure 540-3 Same patient as in Figure 540-1. A, MAG-3 diuretic renogram at 14 mo of age shows equal function in the 2 kidneys. B, Prompt drainage after the administration of furosemide.

excretion is evaluated. After 20 min, furosemide 1 mg/kg is injected Magnetic Resonance Urography intravenously, and the rapidity and pattern of drainage from the MR urography is also used to evaluate suspected upper urinary tract kidneys to the bladder are analyzed. If no obstruction is present, half pathology. The child is hydrated and given intravenous furosemide. of the radionuclide should be cleared from the renal pelvis within Gadolinium-diethylene tetrapentaacetic acid is injected and routine 10-15 min, termed the half-time (t1/2). If there is significant upper tract T1-weighted and fat-suppressed fast spin-echo T2-weighted imaging obstruction, the t1/2 usually is longer than 20 min. A t1/2 of 15-20 min is performed through the kidneys, , and bladder. This study is indeterminate. An elevated t1/2 is suggestive but not diagnostic of provides superb images of the pathology, and methodology permits obstruction. The images generated usually provide an accurate assess- assessment of differential renal function and drainage (Fig. 540-4). ment of the site of obstruction. Numerous variables affect the outcome There is no radiation exposure; however, young children need sedation of the diuretic renogram. For example, newborn kidneys are function- or anesthesia. It is used primarily when renal sonography and nuclear ally immature, and, in the 1st mo of life, normal kidneys might not imaging fail to delineate complex pathology. demonstrate normal drainage after diuretic administration. Patient prolongs parenchymal transit and can blunt the diuretic Computed response. Giving an insufficient dose of furosemide can result in slow In children with a suspected ureteral , noncontrast spiral CT drainage. If vesicoureteral reflux is present, continuous bladder drain- of the abdomen and pelvis is a standard method of demonstrating age is mandatory to prevent the radionuclide from refluxing from the whether a calculus is present, its location, and whether there is signifi- bladder into the dilated upper tract, which would prolong the washout cant proximal hydronephrosis. This study is the initial study of choice phase.. in many of these patients. The disadvantage of CT is the significant The MAG-3 diuretic renogram is considered superior to the excre- radiation exposure, and it should be used only when the results will tory urogram in infants and children with hydronephrosis, because direct management decisions (see Chapter 718). bowel gas and immaturity of renal function often cause the intravenous (IVP) images to be suboptimal. The diuretic renogram pro- Ancillary Studies vides an objective assessment of the relative function of each kidney. In unusual cases, an antegrade pyelogram (insertion of a percutane- ous tube and injection of contrast agent), can be per- Excretory Urogram formed to assess the anatomy of the upper urinary tract. This procedure Excretory urogram is rarely used in assessing the pediatric urinary usually requires general anesthesia. In addition, an antegrade pressure- tract, although it may be useful in selected cases with indeterminate perfusion flow study (Whitaker test) may be performed, in which upper urinary tract obstruction or a suspected duplication anomaly. fluid is infused at a measured rate, usually 10 mL/min. The pressures Part XXIV ◆ Urologic Disorders in Infants and Children 2570

Figure 540-4 MR urogram in boy with distal ureterovesical obstruction.

in the renal pelvis and the bladder are monitored during this infusion, and pressure differences exceeding 20 cm H O suggest obstruction. In 2 Figure 540-5 Retrograde pyelogram showing medial deviation of a other cases, with retrograde pyelography provides excellent dilated upper ureter to the level of the 3rd lumbar vertebra, character- images of the upper urinary tract (Fig. 540-5). istic of a retrocaval ureter. SPECIFIC TYPES OF URINARY TRACT OBSTRUCTION AND THEIR TREATMENT Hydrocalycosis ultrasonogram. After birth, the sonographic study is repeated to The termhydrocalycosis refers to a localized dilation of the calyx caused confirm the prenatal finding. A VCUG is necessary because 10-15% of by obstruction of its infundibulum, termed infundibular stenosis. This patients have ipsilateral vesicoureteral reflux. Because neonatal condition can be developmental in origin or secondary to inflamma- can cause temporary decompression of a dilated renal pelvis, it is ideal tory processes, such as UTI. It usually is discovered during evaluation to perform the first postnatal sonogram after the 3rd day of life. Delay- for pain or UTI. The diagnosis of infundibular stenosis is usually estab- ing the sonogram may be impractical. If no dilation is found on the lished by sonograph and CT scan or MR urography. initial sonogram, a repeat study should be performed at 1 mo of age. If the kidney shows grade 1 or 2 hydronephrosis and the renal paren- Ureteropelvic Junction Obstruction chyma appears normal, a period of observation usually is appropriate, UPJ obstruction is the most common obstructive lesion in childhood with sequential renal ultrasonograms to monitor the severity of hydro- and usually is caused by intrinsic stenosis (see Figs. 540-1 to 540-3). An , and the hydronephrosis usually disappears. pro- accessory artery to the lower pole of the kidney also can cause extrinsic phylaxis is not indicated for children with mild hydronephrosis. If the obstruction. The typical appearance on ultrasonography is grade 3 or 4 hydronephrosis is grade 3 or 4, spontaneous resolution is less likely hydronephrosis without a dilated ureter. UPJ obstruction most com- and obstruction is more likely to be present, particularly if the renal monly manifests on antenatal sonography revealing fetal hydronephro- pelvic diameter is 3 cm. A diuretic renogram with MAG-3 is per- sis; as a palpable renal mass in a newborn or infant; as abdominal, flank, formed at 4-6 wk of age. If there is poor upper tract drainage or the or ; as a febrile UTI; or as hematuria after minimal trauma. differential renal function is poor, pyeloplasty is recommended. After Approximately 60% of cases occur on the left side, and the male : female pyeloplasty the differential renal function often improves, and improved ratio is 2 : 1. UPJ obstruction is bilateral in only 10% of cases. In kidneys drainage with furosemide stimulation is expected. with UPJ obstruction, renal function may be significantly impaired If the differential function on renography is normal, and drainage is from pressure , but approximately half of affected kidneys have satisfactory, the infant can be followed with serial ultrasonograms, relatively normal glomerular function. The anomaly is corrected by even with grade 4 hydronephrosis. If the hydronephrosis remains performing a pyeloplasty, in which the stenotic segment is excised and severe with no improvement, a repeat diuretic renogram after 6-12 mo the normal ureter and renal pelvis are reattached. Success rates are can help in the decision between continued observation and surgical 91-98%. Pyeloplasty can be performed using laparoscopic techniques, repair. Prompt surgical repair is indicated in infants with an abdominal often robotic-assisted using the da Vinci robot. mass, bilateral severe hydronephrosis, a solitary kidney, or diminished Lesser degrees of UPJ narrowing might cause mild hydronephrosis, function in the involved kidney. In unusual cases in which the differ- which usually is nonobstructive, and typically these kidneys function ential renal function is <10% but the kidney definitely has some func- normally. The spectrum of UPJ abnormalities has been referred to as tion, insertion of a tube allows drainage of anomalous UPJ. Another cause of mild hydronephrosis is fetal folds of the hydronephrotic kidney for a few weeks to allow reassessment of the upper ureter, which also are nonobstructive. renal function. In older children who present with symptoms, the The diagnosis can be difficult to establish in an asymptomatic infant diagnosis of UPJ obstruction usually is established by ultrasonography in whom dilation of the renal pelvis is found incidentally in a prenatal and diuretic renography. Chapter 540 ◆ Obstruction of the Urinary Tract 2571

The following entities should be considered in thedifferential diag- ureter, but there may be reflux into the ipsilateral lower pole ureter or nosis: megacalycosis, a congenital nonobstructive dilation of the contralateral collecting system. calyces without pelvic or ureteric dilation; vesicoureteral reflux with Treatment depends on the status of the renal unit drained by the marked dilation and kinking of the ureter; midureteral or distal ure- ectopic ureter. If there is satisfactory function, ureteral reimplantation teral obstruction when the ureter is not well visualized on the urogram; into the bladder or (anastomosing the ectopic and retrocaval ureter. upper pole ureter into the normally inserting lower pole ureter) is indicated. If function is poor, partial or total is indicated. Midureteral Obstruction In many centers this procedure is done laparoscopically and often with Congenital ureteral stenosis or a ureteral valve in the midureter is rare. robotic assistance using the da Vinci robot. It is corrected by excision of the strictured segment and reanastomosis of the normal upper and lower ureteral segments. A retrocaval ureter Ureterocele is an anomaly in which the upper right ureter travels posterior to the A ureterocele is a cystic dilation of the terminal ureter and is obstruc- inferior vena cava. In this anomaly, the vena cava can cause extrinsic tive because of a pinpoint ureteral orifice. Ureteroceles are much more compression and obstruction. An IVP or MR urogram shows the right common in girls than in boys. Affected children usually are discovered ureter to be medially deviated at the level of the 3rd lumbar vertebra. by prenatal ultrasonography, but some present with a febrile UTI. The diagnosis may be confirmed by retrograde pyelography (see Fig. Ureteroceles may be ectopic, in which case the cystic swelling extends 540-5). Surgical treatment consists of transection of the upper ureter, through the bladder neck into the urethra, or orthotopic, in which case moving it anterior to the vena cava, and reanastomosing the upper and the ureterocele is entirely within the bladder. Both orthotopic and lower segments. Repair is necessary only when obstruction is present. ectopic ureteroceles can be bilateral. Retroperitoneal tumors, fibrosis caused by surgical procedures, inflam- In girls, ureteroceles nearly always are associated with ureteral dupli- matory processes (as in chronic granulomatous disease), and radiation cation (Fig. 540-7), whereas in 50% of affected boys there is only 1 therapy can cause acquired midureteral obstruction. Ectopic Ureter A ureter that drains outside the bladder is referred to as an ectopic ureter. This anomaly is 3 times as common in girls as in boys and usually is detected prenatally. The ectopic ureter typically drains the upper pole of a duplex collecting system (2 ureters). In girls, approximately 35% of these ureters enter the urethra at the bladder neck, 35% enter the urethrovaginal septum, 25% enter the , and a few drain into the , , Gartner duct, or a . Often the terminal aspect of the ureter is nar- rowed, causing hydroureteronephrosis. With the exception of the ectopic ureter entering the bladder neck, in girls an ectopic ureter causes continuous urinary incontinence from the affected renal moiety. UTI is common because of urinary stasis. In boys, ectopic ureters enter the posterior urethra (above the exter- nal sphincter) in 47%, the in 10%, the seminal vesicle in 33%, the ejaculatory duct in 5%, and the in 5%. Con- sequently, in boys, an ectopic ureter does not cause incontinence, and most patients present with a UTI or . Evaluation includes a renal sonogram, VCUG, and renal scan, which demonstrates whether the affected segment has significant function. The sonogram shows the affected hydronephrotic kidney or dilated Figure 540-6 Ultrasonographic image of the right dilated ureter upper pole and ureter down to the bladder (Fig. 540-6). If the ectopic (bottom arrows) extending behind and caudal to a nearly empty ureter drains into the bladder neck (female), a VCUG usually shows bladder (top arrow) in a girl with urinary incontinence and ectopic ureter reflux into the ureter. Otherwise, there is no reflux into the ectopic draining into the vagina.

A B

Figure 540-7 A, Infant with ectopic ureterocele. Sonogram of the left kidney shows massive dilation of the upper pole and a normal lower pole. B, Voiding cystourethrogram shows large ureterocele, draining the left upper pole, in the bladder. No reflux is present. Part XXIV ◆ Urologic Disorders in Infants and Children 2572 ureter. When associated with a duplication anomaly, the ureterocele drains the upper renal moiety, which commonly functions poorly or is dysplastic because of congenital obstruction. The lower pole ureter drains into the bladder superior and lateral to the upper pole ureter and may reflux. An ectopic ureterocele extends submucosally into the urethra. Rarely, large ectopic ureteroceles can cause bladder outlet obstruction and retention of urine with bilateral hydronephrosis. In girls, the ure- terocele can prolapse from the urethral meatus. Ultrasonography is effective in demonstrating the ureterocele and whether the associated obstructed system is duplicated or single. VCUG usually shows a filling defect in the bladder, sometimes large, corresponding to the uretero- cele, and it often shows reflux into the adjacent lower pole collecting system with typical findings of a “drooping lily” appearance to the kidney. Nuclear renal scintigraphy is most accurate in demonstrating whether the affected renal moiety has significant function. Treatment of ectopic ureteroceles varies among different medical centers and depends on whether the upper pole functions on renal scan and whether there is reflux into the lower pole ureter. If there is non- function of the upper pole of the kidney and there is no reflux, treat- ment usually involves laparoscopic, robotic, or open excision of the obstructed upper pole and most of the associated ureter. If there is function in the upper pole or significant reflux into the lower pole ureter, or if the patient is septic from infection of the hydronephrotic kidney, then transurethral incision with cautery is appropriate initial therapy to decompress the ureterocele. Reflux into the incised uretero- cele is common, and subsequent excision of the ureterocele and ure- teral reimplantation usually is necessary. An alternative method is to perform a upper-to-lower ureteroureterostomy, allowing the obstructed upper pole ureter to drain through the normal lower ureter; this pro- cedure often is performed with minimally invasive laparoscopic Figure 540-8 Simple intravesical ureterocele. The excretory urogram (robotic) technique or through a small incision. shows left hydronephrosis and a round filling defect on the left side of Orthotopic ureteroceles are associated with duplicated or single the bladder corresponding to a simple ureterocele causing left ureteral collecting systems, and the orifice is in the expected location in the obstruction. This lesion was treated by transurethral incision and drain- bladder (Fig. 540-8). These anomalies usually are discovered during an age of the ureterocele. investigation for prenatal hydronephrosis or a UTI. Ultrasonography is sensitive for detecting the ureterocele in the bladder and hydroure- teronephrosis. IVP reveals varying degrees of ureteral and calyceal sis diminishes gradually (Fig. 540-10). Truly obstructed megaureters dilation, and there is a round filling defect in the bladder. In delayed require surgical treatment, with excision of the narrowed segment, films, cystic dilation of the ureter may be clearly visible and full of ureteral tapering, and reimplantation of the ureter. The results of surgi- contrast material. Transurethral incision of the ureterocele effectively cal reconstruction usually are good, but the prognosis depends on relieves the obstruction, but it can result in vesicoureteral reflux, neces- preexisting renal function and whether complications develop. sitating ureteral reimplantation later. Some prefer open excision of the If differential renal function is normal (>45%) and the child is ureterocele and reimplantation as the initial form of treatment. Small, asymptomatic, it is safe to manage the patient with observation with simple ureteroceles discovered incidentally without upper tract dila- serial ultrasonography and periodic diuretic renography to monitor tion generally do not require treatment. renal function and drainage. In children with grade 4 hydroureterone- phrosis, prophylactic antimicrobial therapy should be prescribed, as Megaureter these children are prone to upper UTI. If renal function deteriorates, Table 540-5 presents a classification of megaureters (dilated ureter). upper urinary tract drainage slows, or UTI occurs, ureteral reimplanta- Numerous disorders can cause ureteral dilation, and many are tion is recommended. Approximately 15% of children with a nonre- nonobstructive. fluxing megaureter undergo ureteral reimplantation. Megaureters usually are discovered during antenatal sonography, postnatal UTI, hematuria, or abdominal pain. A careful history, physi- Prune-Belly Syndrome cal examination, and VCUG identify causes of secondary megaureters Prune-belly syndrome, also called triad syndrome or Eagle-Barrett and refluxing megaureters as well as the prune-belly syndrome. syndrome, occurs in approximately 1 in 40,000 births; 95% of affected Primary obstructed megaureters and nonobstructed megaureters children are male. The characteristic association of deficient abdominal probably represent varying degrees of severity of the same anomaly. muscles, undescended testes, and urinary tract abnormalities probably The primary obstructed nonrefluxing megaureter results from results from severe urethral obstruction in fetal life (Fig. 540-11). Oli- abnormal development of the distal ureter, with collagenous tissue gohydramnios and are common complications replacing the muscle layer. Normal ureteral peristalsis is disrupted, and in the perinatal period. Many affected infants are stillborn. Urinary the proximal ureter widens. In most cases there is not a true stricture. tract abnormalities include massive dilation of the ureters and upper On IVP or an MR urogram, the distal ureter is more dilated in its distal tracts and a very large bladder, with a patent urachus or a urachal segment and tapers abruptly at or above the junction of the bladder diverticulum. Most patients have vesicoureteral reflux. The prostatic (Fig. 540-9). The lesion may be unilateral or bilateral. Significant urethra usually is dilated, and the is hypoplastic. The anterior hydroureteronephrosis suggests obstruction. Megaureter predisposes urethra may be dilated, resulting in a megalourethra. Rarely, there is to UTI, urinary stones, hematuria, and flank pain because of urinary urethral stenosis or atresia. The kidneys usually show various degrees stasis. In most cases, diuretic renography and sequential sonographic of dysplasia, and the testes usually are intraabdominal. Malrotation of studies can reliably differentiate obstructed from nonobstructed mega- the bowel often is present. Cardiac abnormalities occur in 10% of cases; ureters. In most nonobstructed megaureters, the hydroureteronephro- >50% have abnormalities of the musculoskeletal system, including Chapter 540 ◆ Obstruction of the Urinary Tract 2573

Table 540-5 Classification of Megaureter

Refluxing Obstructed Nonrefluxing and Nonobstructed PRIMARY SECONDARY PRIMARY SECONDARY PRIMARY SECONDARY Primary reflux Neuropathic bladder Intrinsic (primary obstructed Neuropathic bladder Nonrefluxing, insipidus megaureter) nonobstructive Megacystic-megaureter Hinman syndrome Ureteral valve Hinman syndrome Infection syndrome Ectopic ureter Posterior urethral Ectopic ureter Posterior urethral Persistent after relief valves valves of obstruction Prune-belly syndrome Bladder diverticulum Ectopic uterocele Ureteral calculus Postoperative Extrinsic Postoperative

infection or reflux and eventually require renal transplantation. Renal transplantation in these children offers good results. Bladder Neck Obstruction Bladder neck obstruction usually is secondary to ectopic ureterocele, bladder calculi, or a tumor of the prostate (rhabdomyosarcoma). The manifestations include difficulty voiding, , UTI, and bladder distention with . Apparent bladder neck obstruction is common in cases of posterior urethral valves, but it seldom has any functional significance. Primary bladder neck obstruc- tion is extremely rare. Posterior Urethral Valves The most common cause of severe obstructive uropathy in children is posterior urethral valves, affecting 1 in 8,000 boys. The urethral valves are tissue leaflets fanning distally from the prostatic urethra to the external urinary sphincter. A slit-like opening usually separates the leaflets. Valves are of unclear embryologic origin and cause varying degrees of obstruction. Approximately 30% of patients experience end- stage renal disease or chronic renal insufficiency. The prostatic urethra dilates, and the bladder muscle undergoes hypertrophy. Vesicoureteral Figure 540-9 Obstructed nonrefluxing megaureter. Excretory reflux occurs in 50% of patients, and distal ureteral obstruction can urogram in a girl with a history of a febrile . The result from a chronically distended bladder or bladder muscle hyper- right side is normal. The left side reveals hydroureteronephrosis with trophy. The renal changes range from mild hydronephrosis to severe predominant dilation of the distal ureter. Note the characteristic renal dysplasia; their severity probably depends on the severity of the appearance of the distal ureter. There was no vesicoureteral reflux. The diagnosis of obstruction was confirmed by diuretic renography. obstruction and its time of onset during fetal development. As in other cases of obstruction or renal dysplasia, there may be and pulmonary hypoplasia. Affected boys with posterior urethral valves often are discovered limb abnormalities and scoliosis. In girls, anomalies of the urethra, prenatally when maternal ultrasonography reveals bilateral hydro­ uterus, and vagina usually are present. nephrosis, a distended bladder, and, if the obstruction is severe, Many neonates with prune-belly syndrome have difficulty with oligohydramnios. Prenatal bladder decompression by percutaneous effective bladder emptying because the bladder musculature is poorly vesicoamniotic shunt or open fetal has been reported. Experi- developed, and the urethra may be narrowed. When no obstruction is mental and clinical evidence of the possible benefits of fetal intervention present, the goal of treatment is the prevention of UTI with antibiotic is lacking, and few affected fetuses are candidates. Prenatally diagnosed prophylaxis. When obstruction of the ureters or urethra is demon- posterior urethral valves, particularly when discovered in the 2nd tri- strated, temporary drainage procedures, such as a vesicostomy, can mester, carry a poorer prognosis than those detected in the 3rd trimester help to preserve renal function until the child is old enough for surgery. following a normal second fetal ultrasound. In the male neonate, pos- Some children with prune-belly syndrome have been found to have terior urethral valves are suspected when there is a palpably distended classic or atypical posterior urethral valves. UTIs occur often and bladder and the urinary stream is weak. If the obstruction is severe should be treated promptly. Correction of the undescended testes by and goes unrecognized during the neonatal period, infants can present orchidopexy can be difficult in these children because the testes are later in life with because of or sepsis caused by located high in the abdomen and surgery is best accomplished in the infection in the obstructed urinary tract. With lesser degrees of obstruc- 1st 6 mo of life. Reconstruction of the abdominal wall offers cosmetic tion, children present later in life with difficulty in achieving diurnal and functional benefits. urinary continence or with UTI. The diagnosis is established with a The prognosis ultimately depends on the degree of pulmonary hypo- VCUG (Fig. 540-12) or by perineal ultrasonography. plasia and renal dysplasia. One third of children with prune-belly After the diagnosis is established, renal function and the anatomy of syndrome are stillborn or die in the 1st few mo of life because of pul- the upper urinary tract should be carefully evaluated. In the healthy monary hypoplasia. As many as 30% of the long-term survivors neonate, a small polyethylene feeding tube (No. 5 or No. 8 French) is develop end-stage renal disease from dysplasia or complications of inserted in the bladder and left for several days. Passing the feeding Part XXIV ◆ Urologic Disorders in Infants and Children 2574

A B C

Figure 540-10 Neonate with primary nonrefluxing megaureter. A, Renal sonogram shows grade 4 hydronephrosis. B, Dilated ureter. Renal scan showed equal function with the contralateral kidney and satisfactory drainage with stimulation. C, Follow-up sonogram at 10 mo shows complete resolution of hydronephrosis.

Figure 540-11 Photograph of a 1,600-g newborn with the prune- belly syndrome. Note the lack of tonicity of the abdominal wall and the wrinkled appearance of the . tube may be difficult, because the tip of the tube can coil in the prostatic urethra. A sign of this problem is that urine drains around the rather than through it. A Foley (balloon) catheter should not be used, because the balloon can cause severe bladder spasm, which can Figure 540-12 Voiding cystourethrogram in an infant with posterior produce severe ureteral obstruction. urethral valves. Note the dilation of the prostatic urethra and the If the serum level remains normal or returns to normal, transverse linear filling defect corresponding to the valves. treatment consists of transurethral ablation of the valve leaflets, which is performed endoscopically under general anesthesia. If the urethra is too small for transurethral ablation, temporary vesicostomy is pre- ferred, in which the dome of the bladder is exteriorized on the lower Favorable prognostic factors include a normal prenatal ultrasono- abdominal wall. When the child is older, the valves may be ablated and gram between 18 and 24 wk of gestation, a serum creatinine level the vesicostomy closed. <0.8-1.0 mg/dL after bladder decompression, and visualization of the If the serum creatinine level remains high or increases despite corticomedullary junction on renal sonography. In several situations, bladder drainage by a small catheter, secondary ureteral obstruction, a “popoff valve” can occur during urinary tract development, which irreversible renal damage, or renal dysplasia should be suspected. In preserves the integrity of 1 or both kidneys. For example, 15% of boys such cases, a vesicostomy should be considered. Cutaneous pyelostomy with posterior urethral valves have unilateral reflux into a nonfunc- rarely affords better drainage when compared with cutaneous vesicos- tioning dysplastic kidney, termed the VURD syndrome (valves, uni- tomy, and the latter also allows continued bladder growth and gradual lateral reflux, dysplasia). In these boys, the high bladder pressure is improvement in bladder wall compliance. dissipated into the nonfunctioning kidney, allowing normal develop- In the septic and uremic infant, lifesaving measures must include ment of the contralateral kidney. In newborn boys with urinary ascites, prompt correction of the electrolyte imbalance and control of the infec- the urine generally leaks out from the obstructed collecting system tion by appropriate antibiotics. Drainage of the upper tracts by percu- through the renal fornices, allowing normal development of the taneous nephrostomy and may be necessary. After the kidneys. Unfavorable prognostic factors include the presence of oligo- patient’s condition becomes stable, evaluation and treatment may be hydramnios in utero, identification of hydronephrosis before 24 wk of undertaken. Posterior valves are diagnosed in some older boys because gestation, a serum creatinine level >1.0 mg/dL after bladder decom- of a poor stream, diurnal incontinence, or a UTI; these boys generally pression, identification of cortical cysts in both kidneys, and persis- are treated by primary valve ablation. tence of diurnal incontinence beyond 5 yr of age. The prognosis in the newborn is related to the child’s degree of hematuria, or . Catheterization of the bladder usually is impos- pulmonary hypoplasia and potential for recovery of renal function. sible. The diagnosis is made by a , in which Severely affected infants often are stillborn. Of those who survive the contrast is injected toward the bladder through a catheter inserted into neonatal period, approximately 30% eventually require kidney trans- the distal urethra. Ultrasonography also has been used to diagnose plantation and 15% have renal insufficiency. In some series, kidney urethral strictures. is confirmatory. Endoscopic treatment transplantation in children with posterior urethral valves has a lower of short strictures by direct vision is often successful success rate than does transplantation in children with normal blad- initially and results in a profoundly improved urinary stream, but often ders, presumably because of the adverse influence of altered bladder the stricture recurs and is found at long-term follow-up. Longer stric- function on graft function and survival. tures surrounded by periurethral fibrosis often require . After valve ablation, antimicrobial prophylaxis is beneficial in pre- Repeated endoscopic procedures generally should be avoided, because venting UTI, because hydronephrosis to some degree often persists they can cause additional urethral damage. Noninvasive measurement for many years. These boys should be evaluated annually with a renal of the urinary flow rate and pattern is useful for diagnosis and follow-up. ultrasonogram, including assessment of somatic In girls, true urethral strictures are rare because the female urethra growth and pressure, urinalysis, and determination of serum is protected from trauma, particularly in childhood. In the past it was levels of electrolytes. Many boys have significant resulting thought that a distal urethral ring commonly caused obstruction of the from a concentrating defect secondary to prolonged obstructive urop- female urethra and UTI and that affected girls benefited from urethral athy. If these children acquire a systemic illness with vomiting and/or dilation. The diagnosis was suspected when a “spinning top” deformity diarrhea, urine output cannot be used to assess their hydration status. of the urethra was found in the VCUG (see Fig. 543-3 in Chapter 543) They can become dehydrated quickly, and there should be a low and was confirmed by urethral calibration. There is no correlation threshold for hospital admission for intravenous rehydration. Some between the radiologic appearance of the urethra in the VCUG and of these patients have , requiring oral bicarbon- the urethral caliber and no significant difference in urethral caliber ate therapy. If there is any significant degree of renal dysfunction, between girls with recurrent cystitis and normal age-matched controls. growth impairment, or , the child should be followed The finding usually is secondary to detrusor–sphincter dyssynergia. closely by a pediatric nephrologist. When vesicoureteral reflux is Consequently, urethral dilation in girls rarely is indicated. present, expectant treatment and prophylactic doses of antibacterial drugs are advisable. If breakthrough UTI occurs, surgical correction Anterior Urethral Valves and Urethral should be undertaken. Diverticula in the Male After treatment, boys with urethral valves often do not achieve Anterior urethral valves are rare. The obstruction is not obstructing diurnal urinary continence as early as other boys. Incontinence can valve leaflets, as occurs in the posterior urethra. Rather, it is a urethral result from a combination of factors, including uninhibited bladder diverticulum in the penile urethra that expands during voiding. Distal contractions, poor bladder compliance, bladder atonia, bladder neck extension of the diverticulum causes extrinsic compression of the distal dyssynergia, or polyuria. Often these boys require urodynamic evalu- penile urethra, causing urethral obstruction. Typically there is a soft ation with urodynamics or videourodynamics to plan therapy. Boys mass on the ventral surface of the penis at the penoscrotal junction. In with noncompliance are at significant risk for ongoing renal damage, addition, the urinary stream often is weak, and the physical findings even in the absence of infection. Overnight catheter drainage has been associated with posterior urethral valves often are present. The diver- shown to be beneficial in boys with polyuria and can help preserve ticulum may be small and minimally obstructive, or, in other cases, renal function. Urinary incontinence usually improves with age, par- may be severely obstructive and cause renal insufficiency. The diagno- ticularly after puberty. Meticulous attention to bladder compliance, sis is suspected on physical examination and is confirmed by the emptying, and infection can improve results in the future. VCUG. Treatment involves open excision of the diverticulum or trans- urethral excision of the distal urethral cusp. Urethral diverticula occa- Urethral Atresia sionally occur after extensive repair. The most severe form of obstructive uropathy in boys is urethral Fusiform dilation of the urethra or megalourethra can result from atresia, a rare condition. In utero there is a distended bladder, bilateral underdevelopment of the corpus spongiosum and support structures hydroureteronephrosis, and oligohydramnios. In most cases, these of the urethra. This condition is commonly associated with the prune- infants are stillborn or succumb to pulmonary hypoplasia. Some boys belly syndrome. with prune-belly syndrome also have urethral atresia. If the urachus is patent, oligohydramnios is unlikely and the infant usually survives. Male Urethral Meatal Stenosis Urethral reconstruction is difficult, and most patients are managed See Chapter 544 for information on urethral meatal stenosis in males. with continent . Bibliography is available at Expert Consult. Urethral Hypoplasia Urethral hypoplasia is a rare form of obstructive uropathy in boys that is less severe than urethral atresia. In urethral hypoplasia, the urethral lumen is extremely small. Neonates with urethral hypoplasia typically have bilateral hydronephrosis and a distended bladder. Passage of a small pediatric feeding tube through the urethra is difficult or impos- sible. Usually a cutaneous vesicostomy must be performed to relieve upper urinary tract obstruction, and the severity of renal insufficiency is variable. The most severely affected boys have end-stage renal disease. Treatment includes urethral reconstruction, gradual urethral dilation, or continent urinary diversion. Urethral Strictures Urethral strictures in boys usually result from urethral trauma, either iatrogenic (catheterization, endoscopic procedures, previous urethral reconstruction) or accidental (straddle injuries, pelvic fractures). Because these lesions can develop gradually, the decrease in force of the urinary stream is seldom noticed by the child or the parents. More commonly, the obstruction causes symptoms of bladder instability, Chapter 540 ◆ Obstruction of the Urinary Tract 2575.e1

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