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Objective To explore the outcomes and prognostic factors associated with fetal megacystis (enlarged bladder). Study design The MEDLINE and EMBASE databases were searched for studies reporting on outcomes of fetal megacystis. The outcomes observed were chromosomal abnormalities, associated structural anomalies, spontaneous resolution, and survival rates. We also evaluated the potential role of fetal gender, oligohydramnios, gestational age at diagnosis, and intrauterine intervention as prenatal prognostic factors. Results The search identified 558 articles in total, and 13 studies (1675 fetuses) were included in this systematic review. The overall incidences of chromosomal abnormalities and associated structural anomalies in fetal megacystis were 10% and 24%, respectively. Spontaneous resolution of megacystis occurred in 32% of fetuses, and 44% of fetuses were born alive and survived until the follow-up. The odds ratio of survival with oligohydramnios was 0.14, and the mean difference in gestational age at diagnosis between survival and non-survival was 3.43 weeks. No significant difference in survival rate was observed between the genders, and an intrauterine intervention did not significantly improve the prognosis. Conclusions A considerable proportion of fetuses with megacystis are born with a good prognosis. Oligohydramnios and lower gestational age at diagnosis are associated with worse outcomes.

Summary Fetal megacystis is variably defined and understood. The literature on fetal megacystis was systematically reviewed, focusing on prenatal diagnosis, associations and outcomes. This yielded a total of 18 primary references and eight secondary references. Fetal megacystis has an estimated first-trimester prevalence of between 1:330 and 1:1670, with a male to female ratio of 8:1. In the first trimester, megacystis is most commonly defined as a longitudinal bladder dimension of ≥7 mm. Later in pregnancy, a sagittal dimension (in mm) greater than gestational age (in weeks) + 12 is often accepted. Megacystis can be associated with a thickened bladder wall, which has been objectively defined as >3 mm. Oligohydramnios is present in approximately half of all cases. The most common underlying diagnosis is posterior urethral valves (57%), followed by urethral atresia/stenosis (7%), prune belly syndrome (4%), megacystis-microcolon-intestinal-hypoperistalsis syndrome (MMIHS) (1%), and cloacal anomalies (0.7%). Karyotype anomalies are found in 15%, and include trisomy 18, trisomy 13 and trisomy 21. Ultrasound imaging alone is often insufficient to enable a definitive diagnosis, although it may indicate that a specific diagnosis is more likely. Overall, about 50% of reported fetuses with megacystis are terminated, but this proportion varies considerably between countries and over time. Prognostic stratification is evolving, with the most important factors being oligohydramnios, gestational age at diagnosis, degree of bladder enlargement, renal hyperechogenicity, karyotype, and sex. Conclusions This review demonstrated some consensus on the ultrasound criteria for defining fetal megacystis, and illustrated the spectrum of pathologies and their relative frequencies that can cause this condition. It also underlined important associated karyotype anomalies. To progress understanding of the natural history of enlarged fetal bladders, more accurate diagnostics are required, and risk stratification needs to be refined to facilitate prenatal counseling.

Evaluation of the kidneys, bladder, and amniotic fluid volume forms part of any standard obstetrical ultrasound. When a fetal genitourinary anomaly is suspected, a more detailed evaluation is necessary. This detailed imaging can be challenging in the setting of decreased or absent amniotic fluid or large maternal body habitus, and in complex malformations. In these situations, magnetic resonance imaging can help to better define the fetal anatomy and provide a more confident and specific prenatal diagnosis.

Objective To describe the diagnostic criteria and outcome of fetal megacystis according to the gestational age at diagnosis. Methods A 7-year retrospective study was carried out from 2004 to 2011, including cases of megacystis referred to 2 prenatal fetal medicine units. The following data were collected and analyzed: maternal age, term at diagnosis (gestational weeks), ultrasonographic and magnetic resonance imaging data, karyotype, decision of the multidisciplinary prenatal team, fetopathology in cases of termination of pregnancy or fetal death, final diagnosis at birth after ultrasonography and voiding cystourethrography, and medical and surgical follow-up. Results Of the 69 fetuses included in this study, 82.6% were males; 26 were diagnosed during the first trimester, 21 during the second, and 22 during the third. During the first trimester, the main etiologies were urethral occlusions and prune-belly syndrome with poor fetal prognosis. Nineteen pregnancies (69%) were terminated for medical reasons including the association with other malformations, poor evolution, or miscarriage. Only 4 children were born alive. The main etiologies of megacystis discovered during the second and third trimesters were vesicoureteral reflux and urethral occlusion. Twenty of 22 fetuses (91%) were born alive when the fetal megacystis was discovered after 27 weeks of gestation. Conclusion Antenatal discovery of megacystis is a complex and challenging prognostic situation. The prognosis depends on the gestational age at discovery. Megacystis is not always associated with obstruction. In a newborn with megacystis, bladder outlet obstruction has to be excluded. Optimal counseling of the involved parents requires a multidisciplinary approach.

Fetal megacystis, an abnormally enlarged bladder identified at any gestational age, may be transient and resolve spontaneously or may be an early manifestation of bladder outlet obstruction. Anterior urethral valves are the most common cause of the rare condition of congenital obstruction of the anterior urethra. Herein is reported the prenatal observation and postnatal management of a case of megacystis with anterior urethral valves. The etiology is reviewed and strategies recommended for patients with these rare entities.

Purpose To investigate the prognostic factors, fetal survival and outcomes for fetuses with severe megacystis. Material and Methods 60 consecutive cases of antenatally diagnosed severe megacystis between 1988 to 2008 were reviewed from a statewide tertiary referral centre for major fetal abnormalities. Normal fetal bladder sagittal length (FBSL) was represented by the approximate linear formula: FBSL=gestational age (GA) in weeks –5. The relative bladder size (as a percentage of normal for that GA) was compared between the survivor group (n=14) and the fetal/neonatal death group (n=17). All terminations were excluded. Results Mean GA at diagnosis was 18.0 weeks (range 11 to 39). In males megacystis was secondary to posterior urethral valves in 33% (n=17), prune belly syndrome in 22% (n=11) and prostatic hypoplasia/atresia in 20% (n=10). Urethral stenosis (n=3), and 1 case each of prune belly, megacystis-microcolon-intestinal hypoperistalsis syndrome, pelvi-ureteric junction obstruction, urethral diverticulum, and urethral ‘S’ band were identified in the 9 female fetuses. The relative bladder sizes of the two groups were similar: survivor group 310.2±108% vs. fetal/neonatal death group 309.8±120%. Fetuses with megacystis and oligohydramnios had an increased risk of death compared to those who had megacystis without oligohydramnios (OR=11.7; 95%CI 2.1– 64.0, p=0.028). The 14 survivors are aged between 4 months and 18 years old. Table 1 . Outcomes of 60 fetuses with severe megacystis Male (n=51) Female (n=9) Terminated 20 7 Vesicocentesis/fetal urinalysis 24 0 Vesicoamniotic shunt 2 0 Cystoscopic laser ablation 4 0 Fetal/neonatal death 16 1 Alive 13 1 Loss to follow-up 2 0 Conclusions Severe megacystis is a serious fetal condition with a wide variety of diagnoses. Mortality is high with or without intervention. Relative bladder size alone does not predict survival. Fetuses with severe megacystis and normal AFI have a higher survival rate.