Juvenile autosomal recessive polycystic kidney disease

Clinical History

Echogenic kidneys in an asymptomatic child.

Imaging Findings

A 7 year old male child with typical sonographic and intravenous Urographic appearances of Infantile Autosomal Recessive Polycystic Kidney Disease, (ARPKD). Antenatal ultrasound examination had revealed bilaterally enlarged, echobright kidneys. The pelvicalyceal systems were normal and the rest of the examination was normal. Term delivery was spontaneous, uneventful and the infant healthy. Biochemistry and blood indices were normal. Post natal ultrasound examination confirmed the appearances found antenatally. The liver still remained normal. There no family history of renal disease. Both parents had normal renal ultrasounds. At six months the infant's clinical and laboratory examinations remained normal. The repeat ultrasound confirmed enlarged echobright kidneys. The left measured 8 cm , the right 9 cm. There were now visible multiple, small, discrete cysts within the medulla. The liver was reported as normal. The diagnosis of Juvenile type Autosomal Recessive Polycystic Kidney Disease was suspected. The child reappeared 7 years later, still clinically well and with normal biochemistry. Ultrasound again revealed large, diffusely bright kidneys. The left measured 8.2 cm and the right 9 cm. The liver now showed diffuse periportal increased reflectivity and generally bright parenchyma, but no architectural distortion. The spleen and portal flow were normal. The liver findings suggested early fibrosis. This new additional finding supported the considered diagnosis of Juvenile Type ARPKD. An Intravenous Urogram confirmed urographic features of "Medullary Sponge Kidneys", yet further support for the diagnosis.

Discussion

Polycystic renal disease is classified as Autosomal Recessive Polycystic Renal Disease (ARPKD) and Autosomal Dominant Polycystic Kidney Disease (ADPKD). The incidence of ARPKD is 1: 40,000 (1). The gene locus for the recessive type has been determined as lying on chromosome 6p. There is no evidence of genetic heterogeneity (2). There appear to be two distinct phenotypes of ARPKD for which the clinical course is established and well recognised. Histologically the conditions are characterised by hyperplasia and dilatation of the interstitial portions of the collecting ducts; their radial orientation is undisturbed. The nephrons are normal (3). The liver is always abnormal (4) and shows mild to moderate periportal fibrosis and biliary ectasia and occasionally there is cyst formation. The degrees of histological abnormality differ in the different presenting groups. The first definable phenotype, 'Infantile ARPKD', presents at birth or early neonatal life with clinically severe renal impairment. Liver disease is not apparent. The diagnosis is obvious. Few infants survive the neonatal age, succumbing to renal failure. 10 – 90 % of the renal tubules are affected in this spectrum of the disease. The kidneys are clinically palpable and on ultrasound the cortices are diffusely bright. The other group, 'Juvenile' type ARPKD, or 'Congenital hepatic fibrosis' to which our case belongs, usually presents insidiously in early childhood or adolescence, typically around 10 years of age, with hepatomegaly and signs of severe portal hypertension. Sometimes this is dramatic with spontaneous massive upper gastrointestinal haemorrhage from bleeding varices. Renal disease is though present, is not always biochemically or clinically apparent. Less than 10% of the collecting ducts are involved in this form of ARPKD. Ultrasound shows normal or enlarged kidneys with variable size cysts in the medulla and cortex. There is severe hepatic fibrosis. The liver shows marked periportal hyperechogenicity and bile duct proliferation. The renal changes can be detected earlier in life, even antenatally, as in our case, without clinical features. In such cases, the possibility of Juvenile type of ARPKD may be raised. However, although abnormalities may be detected by ultrasound, and more recently MRI, neither tests are specific for ARPKD; at this stage, neither is capable of differentiating the condition from atypical ADPKD or other cystic renal diseases. On an intravenous urogram, a faint pyramidal blush akin to renal tubular ectasia and medullary sponge kidney of adulthood, is seen. These two conditions are different pathological entities and are fairly common, and often incidental in the adult population. They are, however, extremely rare in childhood, so the IVU appearances so described can be diagnostic for juvenile ARPKD(5). Although the specific diagnosis is often determined by family history, genetic testing and histology, most new cases are actually mutants. Imaging therefore plays a major role in detecting the earliest signs of disease, in suggesting the possible diagnosis and thereafter in monitoring progression of the disease particularly the earliest signs of liver disease and portal hypertension. Studies have indicated that the prognosis is relatively good, provided that monitoring and control of liver function and portal hypertension are achieved early. Renal impairment is rarely a major clinical problem. Hence the importance for early detection and the appropriate radiological and biochemical follow-up. Repeated sonographic measurement of the kidneys, liver and spleen appears to be the most useful indicator.

Differential Diagnosis List

Final Diagnosis

Juvenile Autosomal Recessive Polycystic Kidney Disease (Congenital Hepatic Fibrosis)

URL:	https://www.eurorad.org/case/631
DOI:	10.1594/EURORAD/CASE.631
ISSN:	1563-4086