Posterior urethral valves: prenatal diagnostic signs and outcome

Urethral valves can be of enormous clinical importance. Both the prognosis for an affected fetus and the indication for a prenatal therapeutic intervention depend to a high degree on the accuracy of the prenatal diagnosis.

The sonographic findings and the results of the postnatal diagnostic workup of 24 boys treated for urethral valves in our institute are analyzed in the present paper.

Out of a group of 900 children, diagnosed prenatally as having urinary tract anomalies, the postnatal diagnostic workup revealed 24 boys suffering from posterior urethral valves. The combination of megacystis, oligohydramnios, and bilateral renal abnormalities was present in 3 boys, and it was only in these cases that urethral valves were correctly identified as the underlying pathology. The largest group (n = 16) of these fetuses presented with bilateral hydronephrosis with and without megaureter. Megacystis in any combination with other findings was detected only in 4 patients. Oligohydramnios as a sign of impaired renal function was observed in four pregnancies. Four children suffered postnatally from beginning renal insufficiency. Eight infants (33%) required some form of respiratory support. This group included the 4 newborns with oligohydramnios during the pregnancy.

Posterior urethral valves represent a rare but severe congenital malformation. They can disrupt the development of the entire urinary tract and may be life-limiting to the affected boy. Only rarely, however, are they manifested as the complete pathological picture on prenatal ultrasound. In most cases, bilateral impairment of the fetal renal development suggests severe subvesical obstruction. Thus in cases with bilateral renal impairment on prenatal ultrasonography, posterior urethral valves are to be excluded postnatally. Oligohydramnios is a predictor of a poor outcome of the renal function.