Does rate matter? The results of a randomized controlled trial of 60 versus 120 shocks per minute for shock wave lithotripsy of renal calculi

Purpose: In this study we prospectively compared 2 rates of shock wave delivery, 60 and 120 shock waves per minute, to determine whether rate affects outcome with the Dornier Lithotripter S, a lithotriptor with an electromagnetic shock wave source, for renal calculi. Materials and Methods: A total of 104 patients with uncomplicated single renal calculus were randomized and treated. Following a single treatment patients were reviewed at 3 months to determine outcome. A plain abdominal x-ray was performed and the size of any residual fragments was noted. Four patients were lost to followup, 1 in the 60 shock waves per minute group and 3 in the 120 shock waves per minute group. Results: Of the 100 patients with complete followup 49 were treated at 60 shock waves per minute and 51 at 120 shock waves per minute. There was no statistically significant difference between mean stone area treated (p = 0.32) or additional analgesic use in the form of patient controlled alfentanil (p = 0.82). A successful outcome was defined by fragments smaller than 4 mm or stone-free status. At 60 shock waves per minute 59% of patients had a successful outcome compared with 61% at 120 shock waves per minute (p = 0.87) following a single treatment. Post-treatment complications were similar in both groups at 8% for 120 shock waves per minute and 10% for 60 shock waves per minute (p = 0.68). Conclusions: There was no significant difference in patient controlled analgesia use, complications or outcome between rates 60 and 120. Contrary to previous studies these results suggest that a slower rate of shock wave delivery during extracorporeal shock wave lithotripsy for renal calculi does not improve treatment efficacy with the Dornier Lithotripter S.