Polycystic kidney disease and inherited nephropathies: SAQ

This neonate has the perinatal form of autosomal recessive polycystic kidney disease, confirmed by the homozygous PKHD1 mutation. The bilateral enlarged echogenic kidneys with oligohydramnios, the respiratory distress from pulmonary hypoplasia, and the severe hypertension are the classical presenting features. His thrombocytopenia and splenomegaly indicate congenital hepatic fibrosis with portal hypertension and hypersplenism, which is a defining feature of ARPKD because the PKHD1 gene product fibrocystin is expressed in both the collecting ducts and the biliary epithelium. ^[2]

Question 1 (10 marks)

Outline your immediate neonatal management and your medium-term surveillance plan for this child, addressing both the renal and hepatic complications. ^[1]

The immediate priority is respiratory support. The pulmonary hypoplasia from oligohydramnios is the leading cause of neonatal mortality in ARPKD, and he needs continued mechanical ventilation with strategies that accommodate the restricted lung capacity caused by the massively enlarged kidneys splinting the diaphragm. I would involve the neonatal and nephrology teams and plan for prolonged respiratory support. ^[1]

Severe hypertension is the next priority. His blood pressure of 95 over 65 in a term neonate is significantly elevated, and untreated hypertension in ARPKD can cause cardiac failure, neurological complications and accelerated kidney damage. I would treat with intravenous antihypertensives, titrated carefully because these infants are exquisitely sensitive to volume and blood pressure changes, and then transition to oral agents, typically a calcium channel blocker or beta-blocker, with ACE inhibitor added cautiously once renal function and electrolytes are stable. ^[1]

Fluid and electrolyte management must account for the polyuria and salt wasting that accompany the impaired concentrating ability of the diseased tubules. I would monitor daily weights, strict input and output, and serum and urine electrolytes closely. Sodium supplementation may be required to maintain intravascular volume and support growth, and I would ensure adequate caloric intake, sometimes via nasogastric feeding, because failure to thrive is a major problem in infantile ARPKD. ^[2]

For medium-term surveillance, the hepatic fibrosis requires the same attention as the renal disease. His thrombocytopenia and splenomegaly already indicate portal hypertension with hypersplenism, and I would monitor platelet counts, liver function, and abdominal ultrasound with Doppler for portal hypertension at regular intervals. Endoscopic screening for oesophageal varices should begin, because variceal bleeding is a life-threatening complication of congenital hepatic fibrosis. As he grows, I would track his renal function with the estimated GFR, blood pressure, urinalysis and growth parameters, and I would begin planning for the eventuality of renal replacement therapy. If he develops both kidney failure and severe portal hypertension, combined liver-kidney transplantation would be considered, because it addresses both complications simultaneously and has been shown to have favourable outcomes in experienced centres. ^[3]