BACKGROUND: Children with primary vesicoureteral reflux (VUR) may be placed on continuous antibiotic prophylaxis (CAP) to reduce the risk of urinary tract infections (UTI). Despite CAP, many children may still develop breakthrough UTIs. It has been suggested that ureteral diameter ratio (UDR) may predict breakthrough UTI in children with primary VUR. We sought to validate this finding in a larger cohort of children with primary VUR on CAP.
METHODS: We reviewed a prospectively maintained database of children with primary VUR at a single children’s hospital from October 2015 to May 2023. Children were treated at clinician discretion. We included children with primary VUR on CAP with available voiding cystourethrogram (VCUG) imaging. UDR was calculated on VCUG by measuring the largest distal ureteral diameter within the false pelvis and dividing by the distance between the bottom of the L1 vertebral body and the top of the L3 vertebral body, as previously described. In children with bilateral VUR, the higher-grade reflux and the larger UDR were used. Children with duplex systems and secondary VUR were excluded. The primary outcome analyzed was breakthrough UTIs. Statistical analysis was conducted using binary logistic regression.
RESULTS: Of the 257 children in the VUR database, 145 met inclusion criteria. The mean age at VCUG was 2.6 years. Females constituted 51.7% of the cohort. VUR grades included grade 1 (9.7%), grade 2 (15.2%), grade 3 (29%), grade 4 (24.1%), and grade 5 (22.1%). The average UDR was 0.323 (range: 0-1.100). For each 0.1 increase in UDR, there was a significant increase in the risk of breakthrough UTI (OR=1.25, 95% CI 1.045-1.494; p=0.014). With a mean follow-up of 3.2 years, 38 (26.2%) children developed a breakthrough UTI while on CAP. UDR was positively associated with VUR grade (r=0.718; p<0.001), hydronephrosis (p=0.003), and hydroureter (p<0.001).
CONCLUSIONS: This is the first and largest study to externally validate UDR as a predictor for breakthrough UTI in children with primary VUR on CAP. While further study is warranted, UDR may assist in personalizing care for children with primary VUR on CAP.
