title: Minimal hydronephrosis in the fetus: clinical significance and implications for management.
abstract: OBJECTIVE
  We further define the natural history and management of minimal fetal hydronephrosis.
  
  
  METHODS
  Experience with minimal fetal hydronephrosis (renal pelvic diameter 4 to 10 mm. before 20 weeks of gestation and 5 to 10 mm. from 20 to 24 weeks) was reviewed for 18 months at New England Medical Center.
  
  
  RESULTS
  The incidence of minimal fetal hydronephrosis was 2.2% in the 5,900 fetuses screened by ultrasound. In 63% of cases prenatal ultrasound was done more than once, and revealed that dilatation of the urinary tract was stable during gestation in 31 (25%), and became normal in 35 (29%) and worse in 11 (9%). A total of 63 patients (103 renal units) followed for up to 1 year underwent postnatal sonography. Those with abnormalities were screened with a voiding cystourethrogram and renal scan, including 40 with normal postnatal ultrasound and no changes on subsequent evaluation. Of the 23 patients with abnormal findings 4 had functionally significant ureteropelvic junction obstruction and 1 had severe vesicoureteral reflux. A retrospective analysis of the sonograms of patients with minimal fetal hydronephrosis and persistence or progression of hydronephrosis revealed calicectasis, progression of minimal fetal hydronephrosis in utero and/or abnormal renal echogenicity in each fetus.
  
  
  CONCLUSIONS
  Our study shows that in a small but significant number of fetuses minimal fetal hydronephrosis will progress, whereas in most it will resolve.
authors.affiliation: Fetal Treatment Program, Tufts University School of Medicine, Boston, Massachusetts, USA.
authors.forename: L
authors.initials: L
authors.lastname: Morin
authors.forename: M
authors.initials: M
authors.lastname: Cendron
authors.forename: T M
authors.initials: TM
authors.lastname: Crombleholme
authors.forename: S H
authors.initials: SH
authors.lastname: Garmel
authors.forename: G T
authors.initials: GT
authors.lastname: Klauber
authors.forename: M E
authors.initials: ME
authors.lastname: D'Alton
mesh_terms: D018450:Disease Progression; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D015994:Incidence; D007231:Infant, Newborn; D011247:Pregnancy; D012189:Retrospective Studies; D013997:Time Factors; D016216:Ultrasonography, Prenatal