The prenatal ultrasonic diagnosis of urethral obstruction and diverticulum of the urinary bladder.

In a 28 year old gravida 2 para 1 an ultrasonogram at 35 weeks of gestation revealed a huge cystic abdominal tumor in fetus. Postpartum ultrasound, excretory urography and micturating cystourethrography showed a trabeculated bladder with a large diverticulum and hydronephrosis due to a posterior urethral valve. The prenatal diagnosis of this anomaly and immediate surgical intervention prevented additional severe damage in the newborn.