title: Fetal megacystis: prediction of spontaneous resolution and outcome.
abstract: OBJECTIVE
  To investigate the natural history of fetal megacystis from diagnosis in utero to postnatal outcome, and to identify prognostic indicators of spontaneous resolution and postnatal outcome after resolution.
  
  
  METHODS
  This was a national retrospective cohort study. Fetal megacystis was defined in the first trimester as a longitudinal bladder diameter (LBD) ≥ 7 mm, and in the second and third trimesters as an enlarged bladder failing to empty during the entire extended ultrasound examination. LBD and gestational age (GA) at resolution were investigated with respect to likelihood of resolution and postnatal outcome, respectively. Sensitivity, specificity and area under the receiver-operating characteristics curve (AUC) were calculated.
  
  
  RESULTS
  In total, 284 cases of fetal megacystis (93 early megacystis, identified before the 18thweek, and 191 late megacystis, identified at or after the 18thweek) were available for analysis. Spontaneous resolution occurred before birth in 58 (20%) cases. In cases with early megacystis, LBD was predictive of the likelihood of spontaneous resolution (sensitivity, 80%; specificity, 79%; AUC, 0.84), and, in the whole population, GA at regression was predictive of postnatal outcome, with an optimal cut-off at 23 weeks (sensitivity, 100%; specificity, 82%; AUC, 0.91). In the group with early megacystis, the outcome was invariably good when resolution occurred before the 23rdweek of gestation, whereas urological sequelae requiring postnatal surgery were diagnosed in 3/8 (38%) cases with resolution after 23 weeks. In the group with late megacystis, spontaneous resolution was associated with urological complications after birth, ranging from mild postnatal hydronephrosis in infants with resolution before 23 weeks, to more severe urological anomalies requiring postnatal surgery in those with resolution later in pregnancy. This supports the hypothesis that an early resolution of megacystis is often related to a paraphysiological bladder enlargement that resolves early in pregnancy without consequences, while antenatal resolution occurring later in pregnancy (after the 23rdweek of gestation) should suggest a pathological condition with urological sequelae.
  
  
  CONCLUSIONS
  In fetal megacystis, LBD and GA at regression can be used as predictors of resolution and outcome, respectively. These parameters could help in fine-tuning the prognosis and optimizing the frequency of follow-up scans. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: F
authors.identifier: http://orcid.org/0000-0001-7003-4984
authors.initials: F
authors.lastname: Fontanella
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Duin
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, Leiden University Medical Centre, Leiden, The Netherlands.
authors.forename: P N
authors.initials: PN
authors.lastname: Adama van Scheltema
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, Erasmus MC University Medical Centre, Rotterdam, The Netherlands.
authors.forename: T E
authors.identifier: http://orcid.org/0000-0001-9949-1476
authors.initials: TE
authors.lastname: Cohen-Overbeek
authors.affiliation: Department of Obstetrics and Gynaecology, Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: E
authors.identifier: http://orcid.org/0000-0002-4432-3691
authors.initials: E
authors.lastname: Pajkrt
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, Radboud University Medical Centre, Nijmegen, The Netherlands.|Department of Obstetrics, Gynaecology and Prenatal Diagnosis, Utrecht University Medical Centre, Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Bekker
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, University Medical Centre, Grow School for Oncology and Medical Biology, Maastricht, The Netherlands.
authors.forename: C
authors.identifier: http://orcid.org/0000-0001-8253-7001
authors.initials: C
authors.lastname: Willekes
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, VU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: C J
authors.initials: CJ
authors.lastname: Bax
authors.affiliation: Department of Obstetrics, Gynaecology and Prenatal Diagnosis, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: C M
authors.identifier: http://orcid.org/0000-0003-1894-0626
authors.initials: CM
authors.lastname: Bilardo
mesh_terms: D004386:Duodenum / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011379:Prognosis; D012372:ROC Curve; D012075:Remission, Spontaneous; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal; D001743:Urinary Bladder / Q000002:abnormalities* / Q000000981:diagnostic imaging* / Q000196:embryology / Q000473:pathology
keywords: lower urinary tract obstruction; megacystis; prenatal diagnosis; pyelectasis