The simple stone score as a predictor of stone-free status following pediatric percutaneous nephrolithotomy.

PURPOSE: To evaluate the predictive performance of the Simple Stone Score (SSS) in pediatric percutaneous nephrolithotomy (PCNL) and compare it with the Stone-Kidney Size (SKS) score, developed specifically for this population. METHODS: Data from 145 consecutive pediatric patients who underwent PCNL between January 2008 and January 2024 were retrospectively analyzed. The SSS, based on largest stone diameter (LSD) and calyceal stone distribution (CSD), was applied. LSD was categorized as < 30 mm, 30–40 mm, or > 40 mm. CSD was classified as Grade I (single calyx or renal pelvis), Grade II (extension into one additional calyx), or Grade III (more than two calyces or complete staghorn stones). Residual fragments < 4 mm were considered clinically insignificant (CIRFs), and both stone-free and CIRF cases were defined as treatment success. The predictive performance of SSS for post-PCNL stone-free status was evaluated. RESULTS: The overall stone-free rate (SFR) was 68.3%, which increased to 74.5% when CIRFs were considered. On multivariate analysis, prior open stone surgery (p = 0.019), previous PCNL (p = 0.001), stone location (p = 0.011), and SSS (p = 0.008) were identified as independent predictors of SFR. Regarding treatment success, previous PCNL (p = 0.004), stone location (p = 0.020), and SSS (p = 0.003) remained significant independent predictors. Receiver operating characteristic curve analysis demonstrated no significant difference between the predictive performance of the SSS and SKS systems. However, decision curve analysis indicated that the SSS model offered a more consistent net clinical benefit. CONCLUSION: This study shows that the SSS is a reliable tool for predicting stone-free status in pediatric PCNL patients, comparable to the SKS and validated for this population.