Anatomic Abnormalities Associated with Hematuria

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Chapter 515 Anatomic Abnormalities Associated with Hematuria

515.2 Autosomal Recessive Polycystic Kidney Disease

Also known as infantile polycystic disease, autosomal recessive polycystic kidney disease (ARPKD) is an autosomal recessive disorder occurring with an incidence of 1 : 10,000 to 1 : 40,000. The gene for ARPKD (PKHD1) encodes fibrocystin, a large protein (>4,000 amino acids) with multiple isoforms.

Clinical Manifestations

The typical child presents with bilateral flank masses during the neonatal period or early infancy. ARPKD may be associated with oligohydramnios, pulmonary hypoplasia, respiratory distress, and spontaneous pneumothorax in the neonatal period. Perinatal demise appears associated with truncating mutations. Components of the oligohydramnios complex including low-set ears, micrognathia, flattened nose, limb-positioning defects, and growth deficiency may be present. Hypertension is usually noted within the first few weeks of life and is often severe and difficult to control. Oliguria and acute renal failure are uncommonly seen, but transient hyponatremia, often in the presence of acute renal failure, often responds to diuresis. Renal function is usually impaired but may be initially normal in 20-30% of patients. Infrequently, ARPKD manifests beyond infancy, in young infants with a mixed clinical picture of renal and hepatic findings: variable degrees of portal hypertension (hepatosplenomegaly, gastroesophageal varices, prominent cutaneous periumbilical veins, reversal of portal vein flow, thrombocytopenia) and variable renal findings that range from asymptomatic abnormal renal ultrasonography to systemic hypertension and renal insufficiency.

In the newborn, clinical evidence of liver disease by radiologic or clinical laboratory assessment is present in about 45% of children. It is believed to be universal by microscopic evaluation. Patients with ARPKD are at risk for developing ascending cholangitis, varices, and hypersplenism related to portal hypertension; they are also at risk for progressive liver fibrosis, which uncommonly leads to overt liver failure and cirrhosis. A subset of older children, and even young adults with ARPKD, present with prominent hepatosplenomegaly and display mild renal disease that is discovered incidentally during imaging studies of the abdomen.

Diagnosis

The diagnosis of ARPKD is strongly suggested by bilateral palpable flank masses in an infant with pulmonary hypoplasia, oligohydramnios, and hypertension and the absence of renal cysts by sonography of the parents (Fig. 515-1). Markedly enlarged and uniformly hyperechogenic kidneys with poor corticomedullary differentiation are commonly seen on ultrasonography (Fig. 515-2). The diagnosis is supported by clinical and laboratory signs of hepatic fibrosis, pathologic findings of ductal plate abnormalities seen on liver biopsy, anatomic and pathologic proof of ARPKD in a sibling, or parental consanguinity. The differential diagnosis includes other causes of bilateral renal enlargement and/or cysts, such as multicystic dysplasia, hydronephrosis, Wilms tumor, and bilateral renal vein thrombosis (Table 515-1). Prenatal diagnostic testing using genetic linkage analysis or direct mutation analysis is available in families with ≥1 affected child.