Posterior urethral valves: inaccuracy of prenatal diagnosis.

This study was undertaken to determine the specificity of prenatal diagnosis of posterior urethral valves. Twenty-two fetuses were diagnosed in utero with posterior urethral valves due to the presence of persistent megacystis and hydronephrosis. Ten cases had oligohydramnios and 12 had normal or increased fluid. Confirmation of diagnosis was not available in 3 fetuses. Only 8 of 19 fetuses had postnatal confirmation of posterior urethral valves. Other anomalies included urethral atresia, ureteral duplication, megacystis/megaureter, reflux and multicystic dysplastic kidney. We conclude that in utero evidence of megacystis and hydronephrosis with or without oligohydramnios is not diagnostic of posterior urethral valves.