A Retrospective Observational Study for Prediction of Stone-Free Status after Single-session of Retrograde Intrarenal Surgery for Renal Stones

Abstract

Introduction: Retrograde Intrarenal Surgery (RIRS) is a preferred minimal invasive treatment modality for renal stones with advantages of being effective and having lower morbidity rates. Aim: To predict the Stone Free Rate (SFR) after RIRS with lower pole and non-lower pole stones. Materials and Methods: The records of 85 consecutive patients who underwent unilateral RIRS from September 2016 to July 2019 were retrospectively analysed. The studied parameters included patient demographics, stone characteristics (size, volume, and attenuation, Lower Pole Infundibulopelvic Angle (LP IPA) and operative time, presence of preoperative Double-J Stent (DJS) and Stone Free Status (SFS). Standard statistical tests were applied with level of significance as p<0.05. Results: Overall success rate was 83.5% (71 cases) while 14 cases had Residual Stones (RS) at 1 month. The mean age of the patients was 41.07±12.25 years. The mean operative time was 68.85±22.3 minutes. Mean stone size and stone volume were higher in the RS group compared to SF (Stone free) group, 15.07±1.5 mm vs. 12.28±1.6 mm, 1187±145 mm3 vs.680.67±289 mm3 respectively (p<0.001; p<0.001). In RS group, 90% (13) cases had IPA<45°, while 80% cases with IPA>45° were stone free. Patients with non-lower pole stones has SFR 2.8 times compared to LP stones (p<0.001). On multivariate analysis, only LP IPA and LP stone location predicts SFS after RIRS. Conclusion: RIRS is effective procedure for renal stones. Stone size, stone volume, LP stone location and LP IPA effectively predict SFR. However, LP IPA and LP stone location are the most significant predictor of SFS, after single session RIRS for solitary renal stone.