Ultrasound Appearance of Congenital Renal Disease: Pictorial Review

Home , Ectopic kidney, Horseshoe kidney, Pelvic kidney, Supernumerary kidney

The Egyptian Journal of Radiology and Nuclear Medicine (2014) 45, 1255–1264

Egyptian Society of Radiology and Nuclear Medicine The Egyptian Journal of Radiology and Nuclear Medicine

www.elsevier.com/locate/ejrnm www.sciencedirect.com

REVIEW Ultrasound appearance of congenital renal disease: Pictorial review

Narrotam A. Patel, Pokhraj P. Suthar *

Department of Radiology, S.S.G. Hospital, Medical College, Vadodara, India

Received 12 April 2014; accepted 27 June 2014 Available online 5 August 2014

KEYWORDS Abstract Congenital renal diseases consist of a variety of entities. The age of presentation and GUT; clinical examination narrow down the differential diagnosis; however, imaging is essential for accu- Renal disease; rate diagnosis and pretreatment planning. Ultrasound is often used for initial evaluation. Computed Congenital; tomography (CT) and MRI provide additional information. Ultrasonography continues to occupy Ultrasonography a central role in the evaluation and detection of congenital renal diseases due to its advantage of rapid scanning time, lack of radiation exposure, cost effective and easy feasibility. 2014 The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license.

Contents

1. Technique...... 1256 1.1. Anomalies related to ascent of kidney...... 1256 1.1.1. Ectopia ...... 1256 1.1.2. Crossed renal ectopia ...... 1256 1.1.3. Horseshoe kidney...... 1257 1.2. Anomalies related to the ureteric bud ...... 1258 1.2.1. Renal agenesis ...... 1258 1.2.2. Supernumerary kidney ...... 1258 1.2.3. Duplex collecting system and ureterocele ...... 1258 1.2.4. Uretero-pelvic junction obstruction ...... 1259 1.2.5. Congenital megacalyces ...... 1260 1.2.6. Congenital megaureter ...... 1260 1.3. Anomalies related to the renal growth ...... 1260 1.3.1. Renal hypoplasia ...... 1260 1.4. Congenital cystic renal disease ...... 1261

* Corresponding author. Address: 5-Durga Nagar Society, Karodiya, Baroda, Gujarat, India. Tel.: +91 9662500537, +91 9825543039. E-mail addresses: [email protected] (N.A. Patel), [email protected] (P.P. Suthar). Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine. http://dx.doi.org/10.1016/j.ejrnm.2014.06.014 0378-603X 2014 The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license. 1256 N.A. Patel, P.P. Suthar

2. Infantile polycystic renal disease – autosomal recessive polycystic kidney disease (ARPKD) – Potter type I...... 1261 3. Multicystic dysplastic kidneys – Potter type II ...... 1261 4. Early onset autosomal dominant polycystic kidney disease (ADPKD) – Potter type III ...... 1261 5. Obstructive cystic renal dysplasia – Potter type IV ...... 1263 6. Summary ...... 1263 Conﬂict of interest ...... 1263 References...... 1263

1. Technique kidney should immediately be performed if the kidney is not identified within renal fossa (Figs. 1 and 2). If the kidney A 3–5 MHz sector or linear transducer is used to scan the uri- ascends too high, it may pass through the foramen of Boch- nary tract. Although no specific preparation is required for dalek and become a true thoracic kidney, ultrasound is helpful scanning the kidneys, fasting optimizes the visualization. to determine if the diaphragm is intact or not. Evaluation of the renal vessels is augmented by adequate patient hydration. Harmonic imaging is often useful for difficult-to- 1.1.2. Crossed renal ectopia scan patients (e.g., obese patient); additional recent software Crossed fused ectopia of the kidney is a rare malformation advances, including compound imaging and speckle reduction, occurring in 0.05–0.1% of the population [3]. There is a recog- may increase lesion conspicuity and decrease artifacts. nized male predilection with a 2:1 male to female ratio. More The kidneys are scanned in the transverse and coronal than 90% of crossed renal ectopia results in fusion. Left- plane. Optimal patient positioning varies; supine and lateral to-right ectopia is thought to be three times more common. decubitus positions often suffice, although oblique and occa- In crossed renal ectopia, both kidneys are found on the same sionally prone positioning may be necessary. Usually, a combi- side. In 85–90% of cases, the ectopic kidney will be fused to nation of sub costal and intercostal approaches is required to the other kidney. The upper pole of the ectopic kidney is evaluate the kidneys fully; the upper pole of the left kidney usually fused with the lower pole of the other kidney. Fusion may be particularly difficult to image without a combination of metanephrogenic blastema does not allow proper rotation of approaches. Varying the degree of respiration can help in or ascent; thus both kidneys are more caudally located, complete evaluation of kidneys. although the uretero-vesical junctions are located normally. On ultrasound, both kidneys are on the same side and are 1.1. Anomalies related to ascent of kidney typically fused with a characteristic anterior or posterior ‘‘notch’’ between the two fused kidneys (Fig. 3) with a Kidneys develop in human embryos in three sets: those are difference in orientation of the 2 collecting systems in the fused pronephrones, mesonephrones and metanephrones. Proneph- kidneys [4,5]. In addition, ultrasonography can give vital infor- rones appears early in the fourth embryological week and rudi- mation on the arterial supply and venous drainage, which can mentary and nonfunctioning [1]. The mesonephrones form late be grossly abnormal. Calyceal dilatation and distortion, in the fourth week and function as interim kidneys until the hydronephrosis and urolithiasis can also be diagnosed with developing metanephrone begins to function in the ninth week. ultrasonography [6,7]. In patient with renal colic, knowing that The metanephrone also known as permanent kidney develops the uretero-vesical junctions are in the normal position is from two sources: those are the ureteric bud and metanephro- particularly important. genic blastema. The ureteric bud forms the ureter, renal pelvis, calices and collecting ducts, interacting with and penetrating the metanephrogenic blastema. This interaction is necessary to initiate ureteric bud branching and differentiation of neph- rone within the blastema. Initially, foetal kidneys are found in the pelvis. With foetal growth, the kidney comes to lie in the upper retroperitoneum in the ninth gestational week. With ascent, the kidneys rotate medially 90 so that the renal pelvis is directed anteromedially. With the kidneys ascended, they derive their blood supply from nearby vessels; adult blood supply is from the abdominal aorta.

1.1.1. Ectopia Failure of kidney to ascend during embryologic development results in a pelvic kidney. Prevalence rate is 1 in 724 paediatric autopsies [2]. These kidneys are often small and abnormally rotated. The ureters are often short; poor drainage and collecting system dilatation predispose to secondary infection and stone formation. The blood supply is often complex; multiple Fig. 1 Ectopia: Transverse sonogram of a new born baby shows arteries may be derived from regional arteries like the internal the absent right kidney in right renal fossa between the liver and iliac artery or the common iliac artery. A search for a pelvic right psoas muscle. Ultrasound appearance of congenital renal disease: Pictorial review 1257

Fig. 2 Ectopia: Transverse sonogram of same patient in right Fig. 3 Crossed renal ectopia: Sagittal sonogram of 10 day old iliac fossa (RIF) demonstrates 31 · 18 mm sized reniform struc- neonate in the left lumbar region demonstrates the lower pole of ture with cortico-medullary differentiation indicating the ectopic the left kidney is fused with the upper pole of the right kidney in right kidney in RIF. left renal fossa with notch in anterior aspect.

Mc Donald and McClellan (1957) classiﬁed crossed ectopic kidney into 4 types

1. Crossed renal ectopia with fusion – 90%. 2. Crossed renal ectopia without fusion –uncommon. 3. Solitary Crossed renal ectopia – very rare. 4. Bilateral Crossed renal ectopia – extremely rare.

Sub types of Crossed renal ectopia [8] (Fig. 4).

(A) Type 1 – inferior crossed fused ectopia, (B) Type 2 – sigmoid or S-shaped kidney, (C) Type 3 – unilateral lump kidney, (D) Type 4 – unilateral disc kidney, (E) Type 5 – L-shaped kidney and (F) Type 6 – superior crossed fused ectopia.

1.1.3. Horseshoe kidney Horseshoe kidneys are the most common type of renal fusion anomaly. Horseshoe kidneys are found in approximately 1 in 400–500 adults and are more frequently encountered in males (M:F 2:1) [9–11]. Horseshoe kidneys occur when metanephrogenic blastema fuses prior to ascent; fusion is usually at the lower pole (95%). The normal ascent of the kidneys is impaired by the inferior mesenteric artery (IMA) which hooks over the isthmus. Typically, the isthmus is composed of func- Fig. 4 Sub types of crossed renal ectopia: (A) Type 1 – inferior tioning renal tissue, although rarely it is made up of fibrous tis- crossed fused ectopia, (B) type 2 – sigmoid or S-shaped kidney, (C) sue. The horse shoe kidney sits anterior to the abdominal great type 3 – unilateral lump kidney, (D) type 4 – unilateral disc kidney, vessels and derives its blood supply from the aorta or other (E) type 5 – L shaped kidney and (F) type 6 – superior crossed regional vessels like inferior mesenteric, common iliac, internal fused ectopia. iliac or external iliac arteries. Abnormal rotation of the renal pelvis often results in ureteropelvic junction obstruction; the horseshoe kidney is thus predisposed to the infection and stone the renal isthmus crossing the midline anterior to abdominal formation. Additional associated anomalies include vesicoure- great vessels (Fig. 5). Hydronephrosis and collecting system teric reflux, collecting system duplication, renal dysplasia, ano- calculi may occur. Unless aware of the typical appearances rectal malformation, rectovaginal fistula, omphalocele, skeletal of a horseshoe kidney, the abnormally rotated and inferiorly abnormality, cardiac abnormality and retrocaval ureter. located kidney results in poor visualization of the inferior pole On ultrasound, horseshoe kidneys are usually lower than and underestimation of the length. This is especially the case if the normal position, and the lower pole projects medially. the patient is scanned prone, and is an additional argument for Transverse imaging of the retroperitoneum will demonstrate scanning patients supine with left and right decubitus positions 1258 N.A. Patel, P.P. Suthar

[10]. Alternatively the renal tissue located anterior to the aorta may be mistaken for retroperitoneal tissue, such as may be seen in lymphoma or metastatic nodal enlargement [10].

1.2. Anomalies related to the ureteric bud

1.2.1. Renal agenesis Renal agenesis may be unilateral or bilateral. Bilateral renal agenesis is a rare anomaly that is incompatible with life. It is traditionally known as the classic Potter syndrome. Renal agenesis and dysgenesis (malformation of the kidney) occur in around one in 1500 births [12]. Unilateral renal agenesis is usually an incidental ﬁnding; the contra lateral kidney of this patient may be quite large secondary to compensatory hypertrophy. Renal agenesis occurs when there is absence of the metanephrogenic blastema, absence of ureteral bud development, or absence of interaction and pene- Fig. 6 Renal agenesis: Sagittal sonogram of 11 year old female tration of the ureteric bud with the metanephrogenic blastema. shows the absent right kidney in right renal fossa between the liver Renal agenesis is associated with genital tract anomalies, and right psoas muscle with adrenal gland resting over right psoas which are often cystic pelvic mass in both men and women. muscle ‘‘Lying down Adrenal Sign’’. Other associated anomalies include skeletal abnormalities, anorectal malformation, and cryptorchidism. On ultrasonography, the kidney is absent (Fig. 6) with absent ipsilateral renal artery, a normal adrenal gland is usually found. The term lying down adrenal sign (Fig. 7) has been ascribed to the elongated appearance of the adrenal not normally moulded by the adjacent kidney [13]. The adrenal gland will be absent in 8–17% of the patients with renal agenesis [1]. It may be difﬁcult to differentiate between renal agenesis and a small, hypoplastic or dysplastic kidney. With all these conditions the contra lateral kidney is enlarged due to compensatory hypertrophy. Usually, the colon falls into the empty renal bed. Care should be taken not to confuse a loop of gut with a normal kidney. Renal vessels are absent on same side (Figs. 12–14).

1.2.2. Supernumerary kidney It is a rare anomaly. It is usually small in size than the normal one and found above, below, in front of or behind the normal Fig. 7 Renal agenesis: Sagittal sonogram of same patient shows normal left kidney.

kidney. The supernumerary kidney often has only a few calices and a single infundibulum. The formation of a supernumerary kidney is likely caused by the same mechanism that gives rise to a duplex collecting system. Two ureteric buds reach the metanephrogenic blastema, which then divides, or alternatively, there are initially two blastema [14]. On ultrasonography an extra kidney will be found.

1.2.3. Duplex collecting system and ureterocele Duplex collecting system is the most common congenital anomaly of the urinary tract, with a reported incidence of 0.5–10% of all live births [12]. Duplication is complete when there are two separate collecting systems and two separate ureters, each with their own ureteric orifice. Duplication is incom- Fig. 5 Horseshoe kidney: Transverse sonogram shows the plete when the ureters join and enter the bladder through a connecting isthmus crossing anterior to the retroperitoneal single ureteral orifice. With complete duplication, the ureters (Aorta) great vessels, with the renal parenchyma of each limb of from the lower pole of the kidney migrate to assume the the horse shoe draping over the spine. normal position, whereas ureter from the upper pole migrates Ultrasound appearance of congenital renal disease: Pictorial review 1259 abnormally to a more medial and inferior ureteral orifice. In complete duplication, the ureter draining the lower pole has a more perpendicular course through the bladder wall making it more prone to reflux. The ectopic ureter from the upper pole is prone to obstruction, giving rise to an ureterocele. On ultrasonography, a duplex collecting system is seen as two central echogenic renal sinuses with intervening, bridging renal parenchyma. Unfortunately, this sign is insensitive and is seen only in 17% of duplex kidneys [15]. Hydronephrosis of the upper pole moiety and visualization of two distinct collecting systems and ureters are diagnostic (Fig. 8). The bladder should be evaluated for ureterocele. An ureterocele will appear as a round, cyst like structure within the bladder. Sometimes it may be large enough to occupy the bladder (Fig. 9). In female patients TVS can detect even small ureterocele [16]. Colour Doppler and spectral analysis can provide additional information about flow dynamics due to transient change in size [17] Fig. 9 Ureterocele: Transverse sonogram of same patient shows (Fig. 10]. The ultrasonographic appearance of a duplex kidney dilatation of the ureter from the upper ureter from upper pole is specific but not sensitive. Ultrasonographic findings provide moiety and a large anechoic cystic structure at left VUJ excellent anatomic information but do not necessarily differen- representing as ureterocele. tiate a bifid renal pelvis from a bifid ureter or from 2 complete ureters [18].

1.2.4. Uretero-pelvic junction obstruction Incidence in paediatric population is at 1 per 1000–2000 new- borns [19]. It is a common anomaly with a 2:1 male predomi- nance. The left kidney is affected twice as frequently as the right kidney. It is bilateral in 10–30% of cases [20]. Patients present with chronic, dull aching back or loin pain. Symptom- atic patients and those with complications like stone, infection or impaired renal function should be treated. There is increased incidence of contra lateral renal agenesis or multicystic dysplastic kidneys (Fig. 11). Most of idiopathic UPJ obstruction is thought to be functional rather than anatomical. On microscopic examination, excessive collagen between muscle bundle, deﬁcient/absent muscle, and excessive longitudinal muscle was found [20]. Sometimes aberrant artery, intrinsic valve or luminal stenosis lead to obstruction. On ultrasonography, hydronephrosis is present to the level of UPJ with marked ballooning of the renal pelvis. A chronic Fig. 10 Ureterocele: Transverse sonogram of same patient on case shows renal parenchymal atrophy (Figs. 12–14). Ureter is application colour Doppler shows ureteric jet. normal. Look at contra lateral kidney for renal agenesis or multicystic dysplastic kidneys using Doppler sonography, the

Fig. 11 Right renal agenesis with left sided PUJ obstruction: Fig. 8 Ureterocele: Sagittal sonogram of 12 year old female Sagittal sonogram of 5 year old female patient shows the absent patient shows central parenchymal separating the upper pole and right kidney in right renal fossa between the liver and right psoas lower pole moieties. There is mild dilatation of both moieties. muscle. 1260 N.A. Patel, P.P. Suthar obstructed kidneys can show higher RIs (resistive indices) (Fig. 15) [21].

1.2.5. Congenital megacalyces Non obstructive enlargement of the calices and being typically unilateral increase the chances of secondary infection and stone formation. It is associated with primary megaureter [22]. On ultrasonography, numerous enlarged clubbed shaped calices are seen. Papillary impression is absent and cortical thickness is maintained.

1.2.6. Congenital megaureter Congenital megaureter also known as megaloureter results in functional ureteric obstruction. Men are affected more often, and the left ureter is typically involved [20]. But bilateral Fig. 14 Right renal agenesis with left sided PUJ obstruction: involvement is seen in 8–50% of patients. In megaloureter dis- Transverse sonogram of same patient demonstrates absent right tal segment of the ureter is aperistaltic which leads to insignif- renal vein. icant distal ureterectasis to progressive hydronephrosis or hydroureter. On ultrasonography, classical ﬁnding is fusiform dilatation of distal third of ureter (>7 mm) sometimes

Fig. 15 Right renal agenesis with left sided PUJ obstruction: Fig. 12 Right renal agenesis with left sided PUJ obstruction: Transverse sonogram of the left kidney in ureteropelvic junction Sagittal sonogram of 5 year old female patient shows marked on application of colour Doppler demonstrates raised RI value. ballooning of the left renal pelvis with abrupt cut off at PUJ.

markedly [23]. Sometimes pyelectasis may be present in long standing cases. Calculi were also noted proximal to adynamic segment.

1.3. Anomalies related to the renal growth

1.3.1. Renal hypoplasia Renal hypoplasia refers to a congenitally small kidney where there is essentially normal residual parenchyma but smaller calyces, lobules and papillae. This is in contrast to renal atrophy where renal development which was initially normal has become smaller as secondary sequel from various other pathol- ogies. In an adult patient the distinction from the latter however can be difﬁcult. Renal hypoplasia can be divided into two broad groups: complete (global) renal hypoplasia and segmental renal hypoplasia (Ask Upmark kidney) [13].If unilateral renal hypoplasia is usually asymptomatic bilateral Fig. 13 Right renal agenesis with left sided PUJ obstruction: renal hypoplasia is present with renal insufﬁciency. On Transverse sonogram of 5 year old female patient demonstrates ultrasonography, the kidney appears small in size but the absent right renal artery. otherwise normal [13]. Ultrasound appearance of congenital renal disease: Pictorial review 1261

1.4. Congenital cystic renal disease

(1) Infantile polycystic renal disease – Autosomal recessive polycystic kidney disease (ARPKD) – Potter type I. (2) Multi cystic dysplastic kidneys – Potter type II. (3) Early onset Autosomal dominant polycystic kidney disease (ADPKD) – Potter type III. (4) Obstructive cystic renal dysplasia – Potter type IV.

2. Infantile polycystic renal disease – autosomal recessive polycystic kidney disease (ARPKD) – Potter type I

Autosomal recessive polycystic kidney disease is one of the commonest inheritable infantile cystic renal diseases, but is Fig. 17 ARPKD: Sagittal sonogram shows multiple micro cysts far less common than autosomal dominant polycystic disease in the left kidney which are not communicating with each other. (ADPKD) which affects adults. The incidence is estimated at 1:20,000–50,000 [24]. There is no recognized gender or racial predilection. Results from a mutation in the PKHD1 gene 3. Multicystic dysplastic kidneys – Potter type II (polycystic kidney and hepatic disease) location on chromosome 6p. This results in bilateral symmetric microcystic disease MCDK develops in utero and the diagnosis is often made occurring in the distal convoluted tubules and collecting ducts. either in antenatal or in the early neonatal period, if an ultra- It may be associated with Caroli disease [25] or congenital sound is performed. It may otherwise go unrecognized and hepatic fibrosis [26,27]. may be a common cause of renal agenesis, following complete On ultrasonography, antenatal ultrasound associated oligo- involution during childhood. The unilateral incidence is esti- hydramnios may be identified. Cysts are initially too small to mated at 1:2500–4000. There may be a predisposition for the resolve but with time may become discernible. Unlike ADPKD left kidney, a slightly higher incidence in males for unilateral the cysts rarely exceed 1–2 cm in diameter (Figs. 16 and 17). MDCK and a higher incidence in females for bilateral MCDK. The kidneys appear enlarged and echogenic but usually retain The affected kidney (or renal segment) has no functioning a reniform shape. Medullary pyramids initially may appear renal tissue and is replaced by multiple cysts. Two main types: hypoechoic compared to cortex, which can give a peripheral pelvi-infundibular and hydronephrotic-obstructive [29]. Pelvi- halo during this stage. They eventually become increasingly infundibular type is most common and multiple small non- hyperechoic and corticomedullary differentiation is eventually communicating renal cysts representing the dilated calyces lost. High-resolution ultrasound (linear-array transducer, and it may sometimes regress spontaneously. In hydrone- 7.5 MHz or greater) allows visualization of numerous cylindri- phrotic-obstructive type a dominant cyst is present in the renal cal cysts in the medulla and cortex, which represent ectatic pelvis. Associated contralateral renal tract abnormalities are collecting ducts [28]. Ultrasound is also useful in assessing common and include vesicoureteric reflux (VUR) – most com- the liver for congenital hepatic fibrosis and may demonstrate mon and seen in up to 20% [30], pelviureteric junction (PUJ) normal or coarsened echotexture, biliary tract cystic change obstruction, ureteral ectopia, vesicoureteric junction (VUJ) (Caroli disease) and portal hypertension. obstruction, and ureterocele. Syndromic associations include Meckel–Gruber syndrome and Zellweger syndrome. A normal life expectancy can be expected as long as the contralateral kidney is normal. Complete spontaneous involution is said to occur in up to 60% of cases, but may take up to 10 years to occur [30]. On ultrasonography, lobulated renal contour with multiple internal cysts of varying sizes and shapes is visible (Fig. 18). The renal parenchyma is usually fibrous and echogenic with absent or small hilar vessels. Real time imaging is extremely useful to exclude any communication with the ureter and between each other.

4. Early onset autosomal dominant polycystic kidney disease (ADPKD) – Potter type III

Autosomal dominant polycystic kidney disease is one of the most common serious hereditary diseases, found in 1:500 to 1:1000 individuals, and by far the most common hereditary Fig. 16 ARPKD: Sagittal sonogram shows multiple micro cysts cause of end stage renal failure (ESRF) and accounts for in the right kidney which are not communicating with each other. 10–15% of all cases of ESRF [13]. The kidneys are normal 1262 N.A. Patel, P.P. Suthar

Fig. 18 Multi cystic dysplastic kidney: Sagittal sonogram in Fig. 19 ADPKD: Few well defined anechoic cystic lesions noted neonate shows multiple anechoic cysts of variable size in the right in the liver in ADPKD patient. kidney which are not communicating with each other. at birth, and with time develop multiple cysts. At the age of 30 years, approximately 68% of patients will have visible cysts by ultrasound. That figure increases over time, such that essentially all patients eventually demonstrate cystic change. By the age of 60 years approx. 50% of patients have end stage renal failure (ESRF). The risk of renal cancer is not increased. Clinical presentation is variable and includes dull flank pain of variable severity and time course, abdominal/flank masses, haematuria, hypertension, and renal functional impairment to renal failure. The majority of cases are inherited in an autosomal dominant fashion. In a minority of cases, no family history is present, and the disease is due to a spontaneous mutation. Two genes have been identified, with slightly differ- ent phenotypes PKD1 and PKD2 [31]. PKD1 is located on chromosome 16p and seen in 85% of cases and presentation is earlier and more likely to progress to end stage renal failure (ESRF). PKD2 is located on chromosome 4q, 15% of cases and is less severe. Associated with cerebral berry aneurysms Fig. 20 ADPKD: Sagittal sonogram in same patient shows found in 6% of patients with ADPKD without a family history multiple well defined anechoic cysts in the right kidney which are of aneurysms and in up to 16% of patients with ADPKD with not communicating with each other with enlarged right kidney. a family history [32], intracranial dolichoectasia in 2–3%, colonic diverticulosis, small bowel diverticula, bicuspid aortic valve, mitral valve prolapse in up to 25%, aortic dissection, cysts in other organs like liver: common (Fig. 19), 75% by age 60 years. The defect results in cystic dilatation of the renal tubules (of all parts of the nephron) in a minority of nephrons. The cysts are variable in size and result in compression of the remainder of the kidney (Figs. 20 and 21), resulting in increased renin and erythropoietin secretion, and gradual renal dysfunction. On ultrasonography, simple renal cysts will appear anechoic with well defined imperceptible walls, posterior acoustic enhancement (amplification) and lateral shadowing (extinc- tion) [31]. Cysts with haemorrhage or infection will demonstrate echogenic material within the cyst, without internal blood flow. Calcification may develop. Renal cell carcinomas in contrast, although usually cystic in the setting of ADPKD, will have solid components of thick septae with blood flow. Perinephric haematomas may be visible and collections of variable echogenicity surrounding the kidney. It should be differ- Fig. 21 ADPKD: Sagittal sonogram in same patient shows entiated with primary renal disease related cysts, autosomal multiple well defined anechoic cysts in the left kidney which are recessive polycystic kidney disease (ARPKD) and medullary not communicating with each other with enlarged left kidney. Ultrasound appearance of congenital renal disease: Pictorial review 1263 cystic disease. 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