Renal volumetry and functional impairment prediction in pediatric vesicoureteral reflux based on contrast-enhanced voiding urosonography.

Background: Contrast-enhanced voiding urosonography (CeVUS) provides a radiation-free alternative for diagnosing vesicoureteral reflux (VUR), but there is limited literature on its utility in evaluating renal volumetric loss and predicting split renal function (SRF) impairment as well as renal scarring (RS). This study aimed to elucidate the impact of VUR and intrarenal reflux (IRR) on renal volume, identify independent risk factors for SRF impairment and RS, and develop a predictive model. Methods: In this retrospective cohort study (from January 2022 to December 2024), 261 children (119 VUR-positive, 142 controls) underwent CeVUS. Renal volume was calculated from two-dimensional (2D) ultrasound measurements using the ellipsoid formula (length × width × depth ×0.523). VUR was graded based on the International Reflux Study Committee criteria (low grade: I-II, moderate grade: III, high grade: IV-V), and IRR was assessed during CeVUS. SRF and RS were evaluated by Tc- Results: Across VUR grades, renal volume decreased progressively, but only high-grade VUR showed a statistically significant reduction. No significant differences in renal volume were observed among low-grade VUR, contralateral negative, and negative control groups. Among high-grade VUR cases, kidneys with IRR were smaller than those without IRR, though not significantly (P=0.11). IRR predominantly involved the upper poles (cumulative prevalence 83%) and showed strong spatial concordance with both SRF impairment [Jaccard similarity 0.72, 95% confidence interval (CI): 0.65-0.78] and RS (Jaccard similarity 0.69, 95% CI: 0.62-0.75). In multivariate logistic regression analysis, frequent urinary tract infections (UTIs), higher VUR grade, and IRR emerged as independent risk factors for SRF impairment (all P<0.05), while older age was an additional risk factor for RS. The prediction model demonstrated discriminative ability with areas under the curve (AUCs) of 0.89 (95% CI: 0.86-0.94) for SRF impairment and 0.92 (95% CI: 0.87-0.96) for RS. Conclusions: High-grade VUR is a primary determinant of renal volume reduction, and IRR demonstrates a potential association with accelerated volume loss. Crucially, frequent UTIs, high-grade VUR, and IRR constitute independent risk factors for SRF impairment, while older age independently predicts RS. The multivariable prediction model achieved strong discriminative capacity, supporting CeVUS as a comprehensive, radiation-free modality for anatomical assessment and functional risk stratification in pediatric reflux nephropathy.