The significant impact of the distal ureteral diameter ratio as predictor of breakthrough urinary tract infections in children with vesicoureteral reflux

Abstract

Purpose: Vesicoureteral reflux (VUR) grade is a factor in assessing risk of clinical outcomes but has poor interobserver reliability. More objective and reliable voiding cystourethrogram (VCUG) parameters including the distal ureteral diameter ratio (UDR) and bladder volume at onset of VUR (Vol) may augment or replace grading systems. We hypothesize that addition of these parameters would provide more reliable prediction of breakthrough UTIs within 1 year of VCUG.

Materials and methods: A retrospective review identified 98 children that had VCUG parameters of both UDR and Vol recorded with follow-up of at least 1 year for inclusion in the study. These patients were then assessed for the primary outcome of occurrence of breakthrough UTIs (BUTI) within 1 year of VCUG. Logistic regression and linear mixed model were used to assess the association of patient clinical characteristics and VCUG parameters with the occurrence of BUTI. Predictive ability of the VCUG parameters was assessed by computing the area under the receiver operating characteristic (ROC) curve (AUC) which were compared to identify which is more predictive of BUTI.

Results: Ninety-eight children had 128 VCUGs with 15 occurrences of BUTI within 1 year of a VCUG. Assessments of the association of patient clinical variables and VCUG parameters with BUTI showed a significant association of increased UDR and high VUR grade with greater risk of BUTI. For UDR, the estimated probability of BUTI at the UDR third quartile was 15.0 % compared to 6.2 % at the UDR first quartile, with BUTI odds ratio of 2.68 (95 % CI: 1.39, 5.19) (p = 0.000). For VUR grade, the estimated probability of BUTI was 31.1 % for grade 4-5 compared to 7.0 % for grade 1-2, with BUTI odds ratio of 5.99 (95 % CI: 1.54, 23.26) (p = 0.019). There was no significant association of BUTI with Vol (as % of PBC), and patients' demographics and clinical history. Comparison of the predictive ability of the three VCUG parameters as predictor of BUTI within 1 year of VCUG using area of the ROC curve showed that UDR was the most predictive with AUC of 0.687 (95 % CI: 0.562, 0.812). AUC was lower for VUR grade, 0.466 (95 % CI: 0.256, 0.675), and Vol, 0.339 (95 % CI: 0.206, 0.472).

Conclusions: A more reliable classification system for VUR, with improved predictive accuracy regarding BUTI, may be developed incorporating UDR. Whether VUR grade can be completely replaced by UDR measurements requires further evaluation with larger number of patients.

Keywords: Grade; Pyelonephritis; Ureteral diameter ratio; Urinary tract infection; Vesicoureteral reflux; Voiding cystourethrogram.