title: Validation of the ureteral diameter ratio for predicting early spontaneous resolution of primary vesicoureteral reflux.
abstract: OBJECTIVE
  Management of primary vesicoureteral reflux (VUR) remains controversial, and reflux grade currently constitutes an important prognostic factor. Previous reports have demonstrated that distal ureteral diameter ratio (UDR) may be more predictive of outcome than vesicoureteral reflux (VUR) grade. We performed an external validation study in young children, evaluating early spontaneous resolution rates relative to reflux grade and UDR.
  
  
  METHODS
  Voiding cystourethrograms (VCUGs) were reviewed. UDR was computed by measuring largest ureteral diameter within the pelvis and dividing by the distance between the L1 and L3 vertebral bodies (Figure). VUR grade and UDR were tested in univariate and multivariable analyses. Primary outcome was status of VUR at last clinical follow-up (i.e. resolution, persistence, or surgical intervention). Demographics, VUR timing, laterality, and imaging indication were also assessed.
  
  
  RESULTS
  One-hundred and forty-seven children (98 girls, 49 boys) were diagnosed with primary VUR at a mean age of 5.5 ± 4.7 months. Sixty-seven (45.6%) resolved spontaneously, 55 (37.4%) had persistent disease, and 25 (17%) were surgically corrected. Patients who spontaneously resolved had significantly lower VUR grade, refluxed later during bladder filling, and had significantly lower UDR. In a multivariable model, grade of VUR (p = 0.001), age <12 months (p = 0.008), ureteral diameter (p = 0.02), and UDR (p < 0.0001) achieved statistical significance. For every 0.1 unit increase in UDR, there was a 2.6 (95% CI 1.58-4.44) increased odds of persistent VUR, whereas a 1.6 (95% CI 0.9-3.0) increased odds was observed for every unit increase in grade.
  
  
  CONCLUSIONS
  Both grade of reflux and UDR were statistically significant in a multivariable model; however, UDR had a higher likelihood ratio and was more predictive of early spontaneous resolution than grade alone. Furthermore, unlike traditional VUR grading where children with grade 1-5 may outgrow reflux depending on other factors, there appears to be a consistent UDR cutoff whereby patients are unlikely to resolve. In the present study, no child with a UDR greater than 0.43 experienced early spontaneous resolution, and only three (4.5%) of those with spontaneous resolution had a UDR above 0.35.
  
  
  CONCLUSIONS
  UDR correlates with reflux grade, and is predictive of early resolution in children with primary VUR. UDR is an objective measurement of VUR, and provides valuable prognostic information about spontaneous resolution, facilitating more individualized patient care.
authors.affiliation: Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, IA, USA.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Arlen
authors.affiliation: Department of Urology, Children's Healthcare of Atlanta, Atlanta, GA, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kirsch
authors.affiliation: Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: Traci
authors.initials: T
authors.lastname: Leong
authors.affiliation: Department of Urology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA. Electronic address: christopher-cooper@uiowa.edu.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Cooper
mesh_terms: D002675:Child, Preschool; D000070621:Cystography; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011237:Predictive Value of Tests; D011379:Prognosis; D012075:Remission, Spontaneous; D012189:Retrospective Studies; D014513:Ureter / Q000000981:diagnostic imaging / Q000473:pathology*; D014718:Vesico-Ureteral Reflux / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy
keywords: Grade; Spontaneous resolution; Ureteral diameter ratio (UDR); Vesicoureteral reflux (VUR)