Prenatal resolution of megacystis possibly caused by spontaneous rupture of posterior urethral valves.

We report herein a case of resolution of severe megacystis, possibly caused by spontaneous rupture of posterior urethral valves during follow-up on a prenatal ultrasound. A 32-year-old woman presented at gestational week 15 for evaluation of fetal bladder enlargement. Prenatal ultrasonography revealed megacystis and posterior urethral dilatation. The longitudinal diameter of the bladder was 25 mm. Megacystis spontaneously resolved at gestational week 16. No association with urinary ascites was observed, and amniotic fluid volume remained normal throughout gestation. A boy was delivered vaginally at week 37. Apgar scores were 8 at 1 minute and 9 at 5 minutes. The neonate voided smoothly. Ultrasonography revealed a thickened bladder wall and normal kidneys and upper urinary tracts. Voiding cystourethrography showed dilatation of the posterior urethra but confirmed normal bladder capacity with smooth voiding and no vesicoureteral reflux. On day 57, remnant valves were incised. Postoperatively, filling cystometry showed a compliant bladder with no involuntary phasic contraction. At 7 months follow-up, the infant was asymptomatic, and ultrasonography showed some improvement of bladder wall thickness. Resolution of megacystis in utero appears to have resulted from spontaneous rupture of the posterior urethral valves. To the best of our knowledge, no similar cases have been previously reported.