A 20-year-old primigravid woman is in the third trimester and has felt minimal fetal movement. An ultrasound scan shows bilaterally enlarged echogenic kidneys and a markedly decreased amniotic fluid index. She gives birth to a stillborn male fetus at 33 weeks' gestation. At autopsy, there are deformations resulting from marked oligohydramnios, including flattening of the facies, varus deformities of the feet, and marked pulmonary hypoplasia. Microscopic examination of the liver shows multiple epithelium-lined cysts and proliferation of bile ducts. Which of the following is the most likely renal disease in this fetus?

Autosomal recessive polycystic kidney disease (ARPKD) most often occurs in children, and this case with the distinctive finding of congenital hepatic fibrosis; most cases have PKHD1 gene mutations encoding for fibrocystin expressed in the kidney, liver, and pancreas. By contrast, autosomal dominant polycystic kidney disease (ADPKD) manifests with renal failure in adults and involves PKD1 and PKD2 gene mutations encoding for polycystin proteins found in renal tubules. Some less common forms of ARPKD are accompanied by survival beyond infancy, and these patients develop congenital hepatic fibrosis. Enlarged kidneys with 1- to 4-cm cysts are characteristic of ADPKD in adults. Perhaps the most common renal cystic disease seen in fetuses and infants is multicystic renal dysplasia (multicystic dysplastic kidney), with focal, unilateral, or bilateral from variably sized cysts, but congenital hepatic fibrosis is not present. Medullary sponge kidney is a benign condition usually found on radiologic imaging of adults. Urethral atresia would produce marked bladder dilation, hydroureter, and hydronephrosis.