Antenatal diagnosis of posterior urethral valves.

The antenatal histories of 42 patients with posterior urethral valves diagnosed between June 1987 and September 1990 were reviewed. The mothers of all patients had at least one ultrasound scan during pregnancy. Despite this, fetal uropathy was diagnosed in only 19 cases. The remaining 23 undiagnosed children presented acutely, all within the first 6 months of life. In 33 of 36 pregnancies scanned before 24 weeks' gestation, fetal urological pathology was undetected. Mean plasma creatinine (pCr) at presentation in the group antenatally diagnosed was 139 mumol/l and in those presenting acutely was 238 mumol/l. All pCr analysed were taken after at least 48 h of life. Renal function as measured by follow-up pCr was better in the antenatally diagnosed group during the first year of life. It would appear that a routine second ultrasound scan at 26 weeks' gestation or later would reveal more cases of posterior urethral valves and this information may improve the outcome in terms of renal function.