Independent predictors of failure of shockwave lithotripsy for ureteral stones employing a second-generation lithotripter

Abstract

Purpose: To define factors associated with the failure of shockwave lithotripsy (SWL) in the treatment of ureteral stones.

Patients and methods: We retrospectively studied 405 men and 283 women (mean age 52.6 years) who underwent SWL with a second-generation lithotripter in the period 1994 to 2001. We evaluated available clinical and radiologic features that might have been related to failure of SWL therapy.

Results: Treatment was successful in 502 patients (73%). The 186 patients (27%) in whom treatment failed underwent endourologic alternatives or open surgery. Multivariate logistic regression analysis revealed that unsuccessful outcome was significantly related to: (1) pelvic ureteral stones (odds ratio [OR] 4.02; 95% CI 1.97, 8.19); (2) stone size >10 mm (OR 3.46; 95% CI 2.16, 5.53); (3) obstruction (OR 1.93; 95% CI 0.99, 3.77); and (4) obesity (OR 1.87; 95% CI 0.95, 3.77). Although the predictive value of each individual parameter was relatively low (15.3%-27.9%) the cumulative risk was 82.95% when patients had all four features. The strongest independent predictors of failure were pelvic stones and stones >10 mm (cumulative predictive value 57.3%).

Conclusions: These variables may enable identification of a subgroup of patients who will fail initial SWL. These patients may be candidates for endourologic alternatives as first-line treatment.