Treatment Outcomes of Retrograde Intrarenal Surgery for Renal Stones and Predictive Factors of Stone-Free

Purpose: The aim of this study was to evaluate the efficacy and safety of retrograde intrarenal surgery (RIRS) for the treatment of renal stones and to analyze the predictive factors for stone-free. Materials and Methods: We retrospectively reviewed the records of patients who underwent RIRS for renal stones from January 2000 to July 2009. We identified 66 RIRSs (63 patients with 3 bilateral renal stones) and collected data. Stone-free and success were respectively defined as no visible stones and clinically insignificant residual stones less than 3 mm on postoperative imaging; predictive factors for stone-free were evaluated. Results: Of the 66 renal stones, 18 stones (27.3%) were located in the upper pole or mid-pole or renal pelvis and 48 (72.7%) in the lower pole with or without others, respectively. The mean cumulative stone burden was 168.9+/-392.5 mm(2). The immediate postoperative stone-free rate was 69.7%, and it increased to 72.7% at 1 month after surgery. The success rate was 80.3% both immediately after the operation and 1 month later. In the multivariate analysis, stone location except at the lower pole (p=0.049) and small cumulative stone burden (p=0.002) were significantly favorable predictive factors for the immediate postoperative stone-free rate. The overall complication rate was 6%. Conclusions: RIRS is a safe and effective treatment for renal stones. The stone-free rate of RIRS was particularly high for renal stones with a small burden, except for those located in the lower pole. RIRS could be considered in selective patients with renal stones.