Modified Seoul National University Renal Stone Complexity score for retrograde intrarenal surgery

The Seoul National University Renal Stone Complexity (S-ReSC) score is a well-validated tool for the prediction of stone-free rate (SFR) after percutaneous nephrolithotomy. We modified the S-ReSC score system for application to retrograde intrarenal surgery (RIRS) and evaluated this score. A total of 88 patients who underwent RIRS from 2011 to 2013 were included. The modified S-ReSC score was assigned according to the number of sites involved in the renal pelvis (#1), superior and inferior major calyceal groups (#2–3), and anterior and posterior minor calyceal groups of the superior (#4–5), middle (#6–7), and inferior calyx (#8–9). If the stone was in the inferior sites (#3, #8–9), one additional point per site was added to the original score. The SFR was examined according to the modified S-ReSC score. To evaluate the predictive accuracy, the area under the receiver operating characteristic curve (AUC) was used and compared with the Resorlu–Unsal Stone (RUS) score. The SFR was 85.2 % and was significantly decreased in the order of low (1–2: 94.2 %), medium (2–4: 84.0 %), and high (>4: 45.5 %) modified ReSC score groups (p < 0.001). AUCs of the modified S-ReSC score (0.806) and score group (0.766) were higher than the AUC of the RUS score (0.692; p = 0.012 and p = 0.040, respectively). The modified S-ReSC score predicts the SFR after RIRS well. Furthermore, its predictive accuracy is higher than that of the RUS score.