Contributed by Mariana Cajaiba, MD
CLINICAL HISTORY AND PATHOLOGIC FINDINGS
This female fetus was the product of elective delivery at 23 weeks of gestational age after a prenatal ultrasound disclosed bilateral multicystic kidneys. A full autopsy was performed. Anthropometric values were adequate for the gestational age. On external examination, no gross malformations were identified; significant abdominal distention was noted. Internal examination revealed massively enlarged kidneys, with poor demarcation between the renal cortex and medulla and numerous cysts throughout the parenchyma, ranging from 0.1 to 0.7 cm in diameter, some of them filled by clear yellow fluid (Figure 1). No other urinary system abnormalities were identified, and both ureters and the urethra were patent. The other organs were grossly normal.
Histological examination of both kidneys showed multiple cysts distributed throughout the cortex and medulla (Figure 2). A single layer of cuboidal epithelium, focally displaying a distinctive brush border, lined the cysts; mild microvesicular steatosis was present. A collar of immature stroma surrounded some cysts, but no metaplastic changes, such as chondroid or myoid differentiation, were identified. In addition, cysts containing glomerular structures were present, but the developing glomeruli at the periphery of the kidney were unaffected. Microscopic evaluation of the liver revealed diffuse micro and macrovesicular steatosis (Figure 3). There were no apparent abnormalities in the biliary tree or hepatic fibrosis. Extramedullary hematopoiesis was also present. The pancreatic acinar cells and uterus also showed severe lipid accumulation (Figures 4 and 5), and the thyroid, adrenal glands and lung showed variable degrees of steatosis. There was also acute and chronic thymic involution, and the placenta showed immature villi for the gestational age and non-hydropic villous edema.
Metabolic studies were performed in amniotic fluid (stored after an amniocentesis) and macerated liver obtained during autopsy, and showed marked elevation of organic acids, including glutaric acid, elevation of unsaturated long fatty acids and markedly decreased carnitine.