Upper tract dilation is an independent risk factor for febrile UTI in children with primary vesicoureteral reflux.

Background: Children with vesicoureteral reflux (VUR), particularly high-grade VUR, are known to be at increased risk for urinary tract infection (UTI). Current guidelines highlight certain clinical factors in the management of children with VUR; however, the clinical utility of upper tract dilation in the setting of VUR remains unclear.

Objective: The purpose of this study is to evaluate risk factors for febrile UTI (fUTI) in children with primary VUR in a modern cohort with emphasis on upper tract dilation parameters, including hydronephrosis and hydroureter.

Methods: A prospectively maintained database of children with VUR at a single academic institution from July 2013 to February 2023 was reviewed. Demographic and clinical data were included. Ultrasounds closest to initial VCUG were reviewed for upper tract dilation, including the presence of hydronephrosis, Society of Fetal Urology (SFU) hydronephrosis grade, presence of hydroureter, and anterior-posterior renal pelvic diameter (APRPD). The primary outcome of interest was the development of a fUTI after VUR diagnosis. Patients were censored after their first fUTI or after VUR surgery.

Results: A total of 235 children with primary VUR were evaluated, including 125 (53.2 %) females and 110 (46.8 %) males. The median age of VUR diagnosis was 10.8 months (IQR: 2.3-63.6 months). A total of 41 (17.4 %) children developed a fUTI after VUR diagnosis with a median follow up of 2.3 years (IQR: 0.9-4.6 years). On univariate analysis, variables found to be associated with fUTI included age <1 year at VUR diagnosis (p = 0.021), female sex (p = 0.013), high-grade VUR (p = 0.024), APRPD ≥7 mm (p = 0.007), high-grade hydronephrosis (p = 0.004), presence of hydronephrosis (p = 0.029), and hydroureter (p = 0.008). In children with VUR and high-grade hydronephrosis, a larger APRPD was associated with higher fUTI rates (p = 0.008). On multivariate analysis controlling for age, sex, and VUR grade, APRPD ≥7 mm (OR 2.8, p = 0.009), high-grade hydronephrosis (OR 2.5, p = 0.025), and presence of hydronephrosis (OR 2.3, p = 0.049) were independent risk factors for fUTI. On multivariate models controlling for other upper tract dilation parameters, APRPD ≥7 mm was the most significant parameter associated with increased fUTI risk in primary VUR.

Conclusion: Upper tract dilation is a novel, independent risk factor for fUTI in children with primary VUR, with APRPD being the strongest predictor. Clinicians may consider upper tract dilation parameters in addition to age, sex, and VUR grade when individualizing care in children with primary VUR.