Modified Seoul National University Renal Stone Complexity Scoring System for Predicting Stone-Free Status After Extracorporeal Shock Wave Lithotripsy

Abstract

Background: Incorporating the modified Seoul National University Renal Stone Complexity (S-ReSC-R) scoring system into the preoperative evaluation of both retrograde intrarenal surgery and percutaneous nephrolithotomy has proven to be highly effective in predicting stone-free status after each procedure. Objective: This study aimed to validate the S-ReSC-R scoring system in extracorporeal shock wave lithotripsy (ESWL) and compare it with the Triple D score under the same protocol. Materials and Methods: Data on consecutive patients undergoing ESWL at a tertiary referral center between 2019 and 2021 were retrospectively analyzed. A total of 297 patients who were evaluated with non-contrast CT prior to the procedure and had adequate follow-up data were included in the analysis. The S-ReSC-R score was calculated based on the number of sites affected. Stone-free status was defined as no evidence of residual stones. Receiver operator characteristic (ROC) curves were generated to determine cutoff values for both scoring systems. Results: The overall stone-free rate (SFRs) after a single session was 60.5%. The average S-ReSC-R score was significantly lower in patients who had successful ESWL than in those with failed ESWL (1.50 vs 2.63, p < 0.001). The SFRs were significantly lower with higher S-ReSC-R scores: 72.4% in the low score (1–2) group, 36.0% in the intermediate score (3–4) group, and 10.5% in the high score (5–12) group (p < 0.001). Multivariate analyses revealed that both the S-ReSC-R score and the Triple D score independently influenced ESWL success (both p < 0.001). The area under the ROC curve for the S-ReSC-R score was 0.767, whereas that for the Triple D score was 0.694. Conclusion: This study confirms that the S-ReSC-R is a reliable tool for predicting stone-free status after ESWL. Thus, its use in evaluating patients for ESWL is recommended.