Prognostic factors for extracorporeal shock-wave lithotripsy of ureteric stones: A multivariate analysis study

To define factors that have a significant impact on the stone-free rate after extracorporeal shock-wave lithotripsy (ESWL) of ureteric stones using multivariate analysis. Between February 1992 and February 2002, a total of 938 patients with ureteric stones were treated with in situ ESWL using the Dornier MFL 5000 lithotripter. The outcome of treatment was evaluated after 3 months and failure was defined as the presence of any residual stones. The stone-free rate was correlated with patient characteristics (age, sex and radiological renal picture) and stone features (site, side, length, width, nature, opacity and the presence of ureteral stents). Factors with a significant impact on the stone-free rate using the chi (2) test were further analyzed using multivariate analysis. Overall, the stone-free rate was 88.7%. Repeat treatment was required in 50.4% of cases. Post-ESWL complications were observed in 32 cases (3.4%), including static steinstrasse in 19 (2%). Auxiliary procedures were needed in 28 cases (3%). Using the chi (2) test, only three factors had a significant impact on the stone-free rate, namely stone site, the transverse diameter of the stone and the presence of a ureteral stent. The stone-free rate was highest for stones located in the lumbar ureter (436/470; 92.8%) and lowest for those located in the pelvic ureter (268/324; 82.7%) (p = 0.0017). Stones with a transverse diameter of < or =1 cm were associated with a stone-free rate of 89.7% (715/797), compared to 83% (114/141) for those with a transverse diameter of >1 cm (p = 0.017). Non-stented patients had a stone-free rate of 89.8% (732/815), compared to 81.3% (100/123) for stented patients (p = 0.006). On multivariate analysis, these three factors maintained their statistical significance. A logistic regression model was designed to estimate the probability of stone-free status after ESWL. 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.