This infant boy weighed 2300 g at birth and was delivered after 33 weeks' gestation. His 32-year-old mother presented in premature labor. The prenatal course had been unremarkable, and no fetal ultrasound examinations were performed. The baby demonstrated respiratory distress at birth and required intubation for supplemental oxygenation. Physical examination revealed a distended abdomen with large bilateral abdominal masses. Urine output was less than 2.0 mL/kg per hour and demonstrated a sodium level of of 43 mmol/L and a potassium level of 35 mmol/L.
An ultrasound study with Doppler evaluation of the major renal vessels (Fig 1) and routine roentgenography of the chest and abdomen were performed.
Multiple indwelling catheters were placed to facilitate both maintenance of adequate fluid levels and electrolyte balance. Hypertension developed shortly after birth and was controlled with difficulty with furosemide, hydralazine hydrochloride, and enalapril. At age 6 weeks, the infant underwent