Predictive factors for stone-free rates and evaluation of mucosal injury using PULS grading system in pediatric ureteroscopy: a single-center experience.

To evaluate the predictive factors for stone-free rates (SFR) in pediatric ureteroscopy and to compare the efficacy and safety of 4.5/6,5 F versus 6/7,5 F semi-rigid ureteroscopes(URS), specifically assessing ureteral wall injury using the Post-Ureteroscopic Lesion Scale (PULS). The data of 114 patients (124 renal units) who underwent semi-rigid URS between 2018 and 2024 were retrospectively reviewed. Stone volume (SV), Hounsfield Unit (HU), and dimensions were calculated from CT images. Procedures were performed using 4.5/6,5–6 F/7,5 F ureteroscopes. The primary outcomes were SFR and ureteral mucosal injury graded by PULS. The overall SFR was 86.2%. In multivariate analysis, stone volume, dimensions, and localization were identified as independent predictors of SFR (p < 0.05), whereas age and stone HU were not. There was no statistically significant difference in SFR between the 4.5 F (88.2%) and 6 F (85.6%) groups (p = 0.76). However, regarding safety, the 4.5 F group exhibited significantly higher rates of lesion-free procedures (PULS 0) and fewer low-grade injuries compared to the 6 F group (p = 0.015). High-grade lesions (PULS 3–4) were observed exclusively in the 6 F group. Semi-rigid ureterorenoscopy is a safe and effective treatment for pediatric ureteral stones. While both 4.5/6.5 F and 6/7.5 F instruments provide comparable success rates, the 4.5/6.5 F URS demonstrates superior safety by significantly minimizing ureteral mucosal injury. Stone volume remains a robust predictor of surgical success.