[Single-session extracorporeal shock wave lithotripsy for urinary calculi: factors predicting success after three weeks of follow-up].

Introduction: The aim of this study was to identify predictive factors of success following a single-session of shock wave lithotripsy (SWL) at 3 weeks of follow-up in our center.

Material And Methods: The medical records of 116 patients with solitary urinary calculi who underwent single-session SWL in our department between October 2007 and August 2009 were reviewed. All preoperative unenhanced computed axial tomographies were reviewed by two radiologists blinded to clinical outcome. Success was defined as complete clearance or the persistence of fragments ≤ 2 mm on a plain film at 3 weeks of follow-up. The impact of clinical and radiological factors on success was assessed by univariate and multivariate analyses.

Results: The single-session SWL success rate at 3 weeks was 49.1%. Stone size <8 mm, stone area < 30 mm(2), stone location (mid- and distal ureter), stone density <1000 HU and intraoperative fragmentation showed a significant association with SWL success in the univariate analysis (p<0.05). Stone area (OR 2.9), ureteral stone location (OR 3.4) and intraoperative fragmentation (OR 4.2) were the only predictors of success in the multivariate analysis.

Conclusions: Stone area and ureteral stone location provide important information when deciding about the indication of a SWL in a patient with stone disease. However, successful resolution of only half of the cases after a single session at 3 weeks in our series undermines the relevance of informing patients about the potential need for additional treatment.