Prenatal detection of megacystis: not always an adverse prognostic factor. Experience in 25 consecutive cases in a tertiary referral center, with complete neonatal outcome and follow-up

Introduction: Megacystis is a condition of abnormal enlarged fetal bladder for gestational age, which is usually associated with urological malformations that may constitute a life-threatening condition for the baby.

Objective: The purpose of this study was to assess the prognostic and etiological criteria of fetal megacystis and to describe the neonatal outcome in a large series collected in a single tertiary center.

Study design: A retrospective observational study was conducted between 2008 and 2012. We reviewed all consecutive cases of fetal megacystis diagnosed during routine ultrasound (US) screening. The following data were collected and analyzed: maternal age, gestational age at diagnosis, prenatal ultrasonographic details of the urinary system, extra-urinary ultrasonographic anomalies, fetal karyotype, pregnancy outcome, postnatal diagnosis, and medical/surgical follow-up.

Results: Of the 25 fetuses included in this study, 76% were males. The mean gestational age (GA) at diagnosis was 23.1 ± 7.5 weeks (range 12-34), among them only four (16%) were diagnosed during the first trimester. Associated urological malformations were detected in 92% (n = 23) of the cases, while other malformations were detected in 36% (n = 9). Oligohydramnios or anyhydramnios were observed in 52% (n = 13) of the cases. Twelve (48%) fetuses were considered as having poor prognosis for renal function. Vesicocentesis with or without vesico-amniotic infusion were performed in 28% (n = 7) of the cases. Pregnancy outcome was surprisingly good, with only one case of prenatal death and survival rate of 96% (n = 24) of liveborn babies. Posterior urethral valve (PUV) (n = 9, 36%) was the most common etiology of the fetal megacystis, followed by persistent urogenital sinus (n = 2, 8%), Prune belly syndrome (n = 2, 8%) and bilateral vescico-ureteral reflux (VUR) (n = 2, 8%). Surgical or endoscopic procedures were performed in 75% (n = 18) of the cases. Six (24%) newborns presented with moderate/severe respiratory distress that requested invasive assisted ventilation. Three cases (n = 3, 12%) of perinatal death were observed due to severe impaired renal function. After a median follow-up of 29 months renal function was good in 79% (n = 19) of the cases.

Conclusions: Fetal megacystis may underline a wide range of associated pathologies with the highest prevalence of urinary malformation. Optimal counseling of the involved parents requires a multidisciplinary approach to allow the best management during the pregnancy and the perinatal period. Despite the high risk of renal failure, lung hypoplasia, and severe associated anomalies, the outcome of fetuses with megacystis could be improved thanks to an appropriate perinatal diagnosis and neonatal management.