title: Mild fetal renal pelvis dilatation: much ado about nothing?
abstract: BACKGROUND
  Renal pelvis dilatation (RPD) occurs in 1% of fetuses. Severe RPD (>15 mm) is frequently associated with urinary tract pathology. For the majority with mild (5 to 9 mm) to moderate (10 to 15 mm) RPD, however, there is uncertainty about the risk of abnormalities and how much postnatal investigation is required.
  
  
  METHODS
  Systematic review of cohort studies of fetuses with RPD < or = 15 mm and metaregression to estimate risks of postnatal RPD, obstruction, and VUR.
  
  
  RESULTS
  Of 506 potentially relevant papers, 18 met the inclusion criteria. Risk of postnatal RPD increased with fetal RP size and earlier gestation. Odds ratios for postnatal RPD doubled per millimeter increase in fetal RP size: At 20 wk gestation, for example, 18% of fetuses with mean RP of 6 mm were estimated to have persistent postnatal RPD, compared with 95% of fetuses with 12 mm RPD, but risks were decreased by 16% to 18% per week of presentation gestation. Estimated risks of obstruction and VUR were substantially lower, particularly in the mild group such as the 6 mm example above: obstruction 2%, VUR 4%.
  
  
  CONCLUSIONS
  Our novel risk estimates are useful for antenatal counseling at presentation. The low frequency of obstruction/VUR in mild RPD raises questions over the most appropriate investigation of these cases but further data are required before establishing definitive postnatal management pathways. We suggest the need for a large prospective multicenter study to collect individual patient parameters/results and search for additional prognostic indicators.
authors.affiliation: Nephro-Urology Unit, University College London Institute of Child Health, London, UK.
authors.forename: Daljit K
authors.initials: DK
authors.lastname: Hothi
authors.forename: Angie S
authors.initials: AS
authors.lastname: Wade
authors.forename: Ruth
authors.initials: R
authors.lastname: Gilbert
authors.forename: Paul J D
authors.initials: PJ
authors.lastname: Winyard
mesh_terms: D003376:Counseling; D004108:Dilatation, Pathologic; D005260:Female; D005865:Gestational Age; D006801:Humans; D007674:Kidney Diseases / Q000196:embryology*; D007682:Kidney Pelvis / Q000000981:diagnostic imaging / Q000196:embryology*; D016017:Odds Ratio; D011247:Pregnancy; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D016216:Ultrasonography, Prenatal; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging / Q000196:embryology*; D014718:Vesico-Ureteral Reflux / Q000000981:diagnostic imaging / Q000196:embryology*