Twelve cases of hydronephrosis in utero diagnosed by ultrasonography.

Twelve examples of hydronephrosis in utero, seven of which were bilateral, were seen at the Johns Hopkins Hospital. Unexpected findings on sonographic examination were: 1) two cases of transient hydronephrosis of moderate severity, persisting over several examinations, which disappeared spontaneously; 2) only two of six examples of ureteropelvic junction obstruction were detected by palpation by competent neonatologists at the time of delivery; 3) polyhydramnios in association with bilateral ureteropelvic junction obstruction was observed in one case and had been reported twice previously (two cases of the prune belly syndrome, however, were associated with oligohydramnios); 4) two examples of a mixed pattern of hydronephrosis and multicystic kidney were seen.