Background: Preoperative determination of patient characteristics and the complexity of renal calculi is essential for optimizing the outcomes of percutaneous nephrolithotomy (PCNL). The Seoul National University Renal Stone Complexity (S-ReSC) scoring system is a popular system for predicting stone-free rates (SFR).

Objective: To assess the predictive accuracy of the S-ReSC scoring system for PCNL in an external cohort.

Materials and Methods: The perioperative data of consecutive patients undergoing PCNL in the standard prone position from January 2011 until August 2020 and S-ReSC scores assigned preoperatively were retrospectively analysed.

Results: The study included 270 patients undergoing PCNL. The mean S-ReSC score was 5.4±2.9. The overall SFR was 60.7%. The SFRs in the low- (1 to 2), intermediate- (3 to 4), and high-score (5 to 9) groups were 100%, 97.8%, and 27.3%, respectively. Multivariate logistic regression showed that the S-ReSC score, stone size, number of stones, and operative time were independent predictors of the stone-free status after PCNL (p<0.001, p=0.015, p=0.004, and p=0.015, respectively). The area under the curve of the S-ReSC score was 0.949, indicating high predictive accuracy. Moreover, the S-ReSC score significantly correlated with estimated blood loss (r=0.15; p=0.014), and operative time (r=0.14; p=0.025).

Conclusion: The S-ReSC score is highly useful for nephrolithiasis assessments and is a reliable predictor of the SFR, bleeding and operative time.

Keywords: Renal calculus; S-ReSC; Percutaneous nephrolithotomy; Stone-free rate