Evaluation of the predictive accuracy of scoring systems for retrograde intrarenal surgery in a pediatric population

BACKGROUND: To assess the predictive accuracy of the retrograde intrarenal surgery (R.I.R.S.) nomogram and Resorlu-Unsal Score (RUSS) in pediatric patients undergoing RIRS. METHODS: This retrospective study included 91 children (≤ 15 years) treated with RIRS between 2016 and 2024. Demographic, anatomical, and stone-related data were analyzed. Stone-free status (SFS) was defined as residual fragments < 2 mm at 4 weeks. Predictive factors were assessed by multivariate binary logistic regression analysis, and scoring systems were evaluated with Receiver Operating Characteristic (ROC) curve analysis. RESULTS: SFS was achieved in 53 patients, while 38 had residual fragments. Independent predictors included stone diameter ≥ 15 mm, infundibulopelvic angle ≤ 30°, renal infundibular length ≥ 25 mm, and multiple stones. Both scoring systems showed high predictive performance: the R.I.R.S. nomogram achieved an AUC of 0.911 (95% CI: 0.855-0.967) and RUSS an AUC of 0.876 (95% CI: 0.806-0.947); formal comparison by DeLong's test showed no statistically significant difference (p = 0.337). R.I.R.S. score ≤ 6 provided optimal sensitivity (94.3%) and specificity (73.7%). CONCLUSIONS: Stone size and anatomy significantly affect RIRS outcomes in children. Both the R.I.R.S. nomogram and RUSS demonstrated high predictive performance, with no statistically significant difference between their AUC values on formal comparison. Either scoring system may support preoperative assessment, though clinical decisions should be individualized.