Antenatal diagnosis of renal anomalies with ultrasound. I. Obstructive uropathy.

During a 5-year period, a diagnosis of obstructive uropathy was made in 25 fetuses. Eight of them had unilateral obstruction and 17 were affected bilaterally. The most common condition encountered was urethral obstruction by posterior valves. The site and nature of the obstruction were correctly identified in 22 of the 25 fetuses. Among the 17 who had bilateral obstruction, only three survived. In contrast, only one infant with unilateral obstruction died (of unrelated causes). Oligohydramnios in low-level (urethral) obstruction was a uniformly lethal finding. Relief of urethral obstruction in two fetuses after 20 weeks of gestation did not result in survival of the infant, whereas shunting prior to 20 weeks in one fetus seemed to have a beneficial effect. On the basis of this experience, we suggest that unilateral obstruction would be treated best by conservative management, while in bilateral obstruction invasive treatment may be effective if initiated early in gestation, before significant oligohydramnios occurs.