Pediatric Renal and Adrenal Masses Part 2

Part 2 review of pediatric renal and adrenal masses for radiology board review. Download the free study guide for this episode by clicking here.

Show Notes/Study Guide:

A multilocular cystic mass arising from the kidney of a young male child showing a claw or beak sign with classic anechoic internal fluid and possible septal enhancement with no nodular or solid internal enhancement makes one think of which classic pediatric renal entity?

This describes the classic imaging appearance of a pediatric cystic nephroma. Note if solid nodular enhancing components are seen this would be most suspicious for a cystic Wilms tumor.

At what age does renal cyst formation occur in multicystic dysplastic kidney?

This is slightly a trick question as the cysts in multicystic dysplastic kidney occur in utero. This diagnosis is usually made antenatally or in the first few months of life on ultrasound, if performed. In some cases, it may go undetected with risk of renal agenesis during childhood. Note that there is loss of renal function in the areas of renal involvement with multicystic dysplastic kidney. Therefore, bilateral extensive renal involvement is fatal.

What are classic imaging findings of multicystic dysplastic kidney?

On ultrasound classic imaging findings are echogenic kidneys with multiple internal clustered non-communicating cysts of different shapes and sizes. These will be T2 bright on MRI.

On a MAG3 nuclear medicine scan poor or absent uptake in areas of multicystic dysplastic kidney involvement are seen. If extensive involvement no renal excretion of radiotracer will be present. Obstructive uropathy may be seen.

True or false? There is up to a 50% rate of contralateral renal tract anomalies in cases of multicystic dysplastic kidney.

True. This can include contralateral vesicoureteral reflux, ureteroceles, renal agenesis or hypoplasia, and/or renal tract obstruction.

What are imaging findings of autosomal recessive polycystic kidney disease?

Ultrasound classically shows enlarged and echogenic kidneys that contain multiple typically small cysts. Look also for co-existing liver abnormalities including a coarse hepatic echotexture and biliary cystic changes. When advanced, changes of portal hypertension may be evident including hepatic fibrosis, splenomegaly, and venous collaterals. Note that early in disease on antenatal ultrasound the cysts may be too small to perceive.

True or false? Autosomal recessive polycystic kidney disease is more common than autosomal dominant polycystic kidney disease.

False. Autosomal dominant polycystic kidney disease is more common.

What is the classic age of presentation for autosomal recessive polycystic kidney disease?

This is a bit of a trick question. The age of presentation can vary, and the disease manifests differently depending on whether disease onsets earlier or later in the pediatric period. In general, those cases seen earlier in life in the neonatal period have renal predominant involvement and those that present later have liver predominant disease. The perinatal presentation with renal predominant disease is, however, the most common. Unfortunately, most of these perinatal disease states are not survivable and most will not survive 24 hours past delivery.

What are some classic causes of pediatric obstructive cystic renal dysplasia?

Urethral or bladder outlet obstruction can, over time, cause cystic dysplasia of the kidney. Classic cases of obstruction to remember for board exams include posterior urethral valves, duplicated collecting system with obstruction from a ureterocele, and urethral agenesis.

This leads us to two classics, often tested concepts for board exams that are worth reviewing now. First, the Weigert-Meyer Rule states that the upper pole moiety is ectopic and prone to obstruction and the lower pole moiety is prone to reflux. Second, reminder that about half of cases of obstructive renal tract pathology in the pediatric population have a VACTERL association with V for Vertebral anomalies, A for Anorectal anomalies, C for Cardiac anomalies, TE for Treacheo-Esophageal fistula, R for Renal anomalies, and L for Limb anomalies.

What is the classic triad of Meckel-Gruber syndrome?

1.     Multiple renal cysts (renal cystic dysplasia). This is mandatory.

2.     Occipital encephalocele or holoprosencephaly.

3.     Polydactyly

What pediatric renal anomaly is classic with tuberous sclerosis?

Renal angiomyolipomas are classic with tuberous sclerosis, seen in up to 75% of tuberous sclerosis cases and typically will be bilateral and large.  These can grow to large size raising risk for hemorrhage for which surgical resection may be performed to prevent.  Co-existing renal cysts may be present. Other common imaging findings include cardiac rhabdomyomas as well as cortical and subependymal tubers. Additional disease involvement with various other manifestations is beyond the scope of the current discussion.

What are some classic features of Zellweger syndrome?

This is a multisystem disease process sometimes termed cerebrohepatorenal syndrome. This typically presents in the neonatal period and is caused by peroxisomal metabolism derangements. Renal manifestations include hyperechoic kidneys. Hepatomegaly may be present. CNS findings include periventricular pseudocysts as well as polymicrogyria and pachygyria.

What are potential renal manifestations of sickle cell disease?

Renal enlargement is often present with bilateral echogenic pyramids on ultrasound.  As disease progresses the kidneys that once were large may ultimately become small with loss of normal function leading ultimately in some cases to renal failure. Renal papillary necrosis and vascular thrombosis such as renal vein thrombosis may also be present.

True or false? If a renal cell carcinoma occurs in a pediatric patient a genetic component is more likely to be present.

True. Certain genetic anomalies and syndromes increase the prevalence of renal cell carcinomas diagnosed in the pediatric population. For example, a translocation of Xp 11.2 is associated with development of pediatric renal cell carcinomas. It remains important to remember that renal cell carcinoma is primarily a renal disease of adults.

What are classic causes of a renal pseudotumor in the pediatric population?

A renal abscess, renal infarct, persistent fetal lobulation, dromedary hump, or prominent column of Bertin are all potential causes of a renal pseudotumor, meaning an imaging finding that looks tumor-like but is not.

What are key imaging findings to help distinguish a column of Bertin from a true renal mass?

A column of Bertin is normal renal cortical tissue that separates the normal renal pyramids, present in about half of individuals overall.  When this becomes prominent enough, it can appear like a mass on imaging. A column of Bertin is in continuity with the normal renal parenchyma, typically located in the mid kidney. The tissue in the column of Bertin should have identical imaging appearance to the renal cortex, such as identical echogenicity on ultrasound. CT and MRI also show that the hypertrophied or prominent column of Bertin has identical imaging features including an identical degree of enhancement to the renal cortex. The renal outline or contour will be preserved with a column of Bertin and is typically distorted with a malignant mass.

What is a persistent fetal lobulation?

The kidney forms embryologically as several distinct lobules that fuse as they grow into what becomes the single kidney.  A persistent fetal lobulation is the incomplete fusion of renal lobules that leave a lobulated or mass-like contour that can almost look like a partially exophytic renal mass.  If there are multiple persistent lobulations an abnormal multilobulated contour of the kidney is seen.

What is the classic ultrasound appearance of pyelonephritis with a renal abscess?

On ultrasound, pyelonephritis may appear as abnormal renal hypoechogenicity with possible perinephric fluid. If an abscess is present this would appear as a well-defined hypoechoic area, typically close to the cortex or the corticomedullary portion of the kidney.

True or false? Multicystic dysplastic kidney is a potential cause of pediatric hydronephrosis.

True. The obstructive type of multicystic dysplastic kidney can result in hydronephrosis.  It is this type of multicystic dysplastic kidney that you would typically see multiple renal pelvis predominant cyst(s).

The pelvi-infundibular type of multicystic dysplastic kidney, on the other hand, is more common and has multiple non-communicating typically small renal cysts and is associated often with atresia of the ureter and renal pelvis.  So, presence or absence of hydronephrosis can help distinguish between subtypes of multicystic dysplastic kidney.

What are other potential causes of pediatric hydronephrosis?

The most common cause of pediatric hydronephrosis is pelviureteric junction (PUJ) obstruction, accountable for about half of cases of pediatric hydronephrosis.  Other common causes include posterior urethral valves, vesicoureteral reflux, vesicoureteral junction (VUJ) obstruction, and megacystis megaureter.

What are the four grades of pediatric hydronephrosis?

Grade 1: mildly dilated renal pelvis and no dilation of the calyces.

Grade 2: moderately dilated renal pelvis with mild calyceal dilatation.

Grade 3: dilatation of both the renal pelvis and the calyces.

Grade 4: the above plus a thinned renal cortex.