The surgical experience influences the safety of retrograde intrarenal surgery for kidney stones: a propensity score analysis.

The aim of this study is to evaluate if surgical experience could influence the outcomes of retrograde intrarenal surgery (RIRS) in terms of stone clearance and complication rate. Patients from five institutions were included in this study. Patients were divided into two groups. Group 1: patients treated by three surgeons in the early phase of learning curve (surgical experience <100 procedures); Group 2: cases operated by two surgeons with great endourological experience (>400 procedures). Patients and stone characteristics, outcome and complications were analyzed. Multivariable regression model was used. Differences between groups were estimated using propensity scores to adjust for the bias inherent to the different characteristics. 381 RIRS were analyzed (Group 1: 150 RIRS; Group 2: 231 RIRS). Clinical data and stone parameters were comparable. The SFR was 70 % in Group 1 and 77.9 % in Group 2 (p = 0.082). Operative time was significantly shorter in the Group 2 (76.3 vs. 53.1 min, p = 0.001). The overall complication rate was significantly lower in Group 2 (20.7 vs. 8.7, p = 0.001). At unadjusted analysis, a non-significant difference was found between centers on SFR (OR 1.51 95 % CI 0.95-2.41). Conversely, a significant difference was found on overall complications (OR 0.36 95 %CI 0.20-0.67) with lower overall complication in Group 2. This study shows that surgeon experience influences the outcomes of RIRS mainly in terms of safety. Further studies will be needed to assess the exact number of procedures necessary to obtain a plateau in the rate of complications and success.