title: Resolution rate of isolated low-grade hydronephrosis diagnosed within the first year of life.
abstract: OBJECTIVE
  Diagnosis of low-grade hydronephrosis often occurs prenatally, during evaluation after urinary tract infection (UTI), or imaging for non-urologic reasons within the first year of life. Its significance in terms of resolution, need for antibiotic prophylaxis, or progression to surgery remains uncertain. We hypothesized that isolated low-grade hydronephrosis in this population frequently resolves, UTIs are infrequent, and progression to surgical intervention is minimal.
  
  
  METHODS
  Children < 12 months old diagnosed hydronephrosis (Society for Fetal Urology [SFU] grade 1 or 2) between January 2004 and December 2009 were identified by ICD9 code. Patients with other urological abnormalities were excluded. Stability of hydronephrosis, UTI (≥ 100,000 CFU/mL bacterial growth) or need for surgical intervention was noted.
  
  
  RESULTS
  Of 1496 infants with hydronephrosis, 416 (623 renal units) met inclusion criteria. Of 398 renal units with grade 1 hydronephrosis, 385 (96.7%) resolved or remained stable. Only 13 (3.3%) worsened, of which one underwent ureteroneocystostomy. Of 225 renal units with grade 2 hydronephrosis, 222 (98.7%) resolved, improved or remained stable, three (1.3%) worsened, of which one required pyeloplasty. Only 0.7% of patients in the ambulatory setting had a febrile UTI.
  
  
  CONCLUSIONS
  Low-grade hydronephrosis diagnosed within the first year of life remains stable or improves in 97.4% of renal units. Given the low rate of recurrent UTI in the ambulatory setting, antibiotic prophylaxis has a limited role in management.
authors.affiliation: Division of Urology, Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Ramiro J
authors.initials: RJ
authors.lastname: Madden-Fuentes
authors.affiliation: Department of Urology, Boston Children's Hospital, Boston, MA, USA.
authors.forename: Erin R
authors.initials: ER
authors.lastname: McNamara
authors.affiliation: Division of Urology, University of California, San Diego, CA, USA.
authors.forename: Unwanaobong
authors.initials: U
authors.lastname: Nseyo
authors.affiliation: Division of Urology, Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Wiener
authors.affiliation: Division of Urology, Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Routh
authors.affiliation: Division of Urology, Department of Surgery, Duke University Medical Center, Durham, NC, USA. Electronic address: sherry.ross@dm.duke.edu.
authors.forename: Sherry S
authors.initials: SS
authors.lastname: Ross
mesh_terms: D000367:Age Factors; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D017063:Outcome Assessment, Health Care; D012720:Severity of Illness Index; D014552:Urinary Tract Infections / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D000900:Anti-Bacterial Agents
keywords: Hydronephrosis; Infants; Urinary tract infection