Prediction of success of extracorporeal shock wave lithotripsy in the treatment of ureteric stones

Objectives To define the factors that affect the success rate of extracorporeal shock wave lithotripsy (ESWL) for the treatment of ureteric stones. Patients and methods Between January 2000 and December 2003, 468 patients with ureteric stones underwent in situ ESWL using Storz SL 20 lithotriptor. The results of treatment were evaluated after 3 months of follow-up. Treatment success was defined as complete clearance of the stones. Characteristics of the patients, condition of the urinary tract and stone features were correlated to the success rate to define the significant predictors of success. Results At 3-month follow-up, the overall success rate was 394/468 (84.2%). Repeat treatment was required in 239 patients (51.1%). Post-ESWL auxiliary procedures were necessary in 58 patients (12.4%). Post-ESWL complications were observed in 11 patients (2.4%). Only three factors had a significant impact on the stone-free rate, namely stone site, stone width and the presence of a ureteral stent. The stone-free rate was highest for stones located in the lumbar ureter (159/183; 86.9%) and lowest for those in iliac ureter (28/40; 70%) (P < 0.05). Stones with a transverse diameter <8 mm were associated with a stone-free rate of 89.9% (248/276), compared to 66.7% (128/192) for those with a transverse diameter of >8 mm (P < 0.01). Non-stented patients had a stone-free rate of 89.2% (313/348), compared to 75.2% (85/113) for stented patients (P < 0.01). Conclusions The site and transverse diameter of the stone and the presence of a ureteral stent are the only significant predictors of success of ESWL therapy for ureteric stones.