Shock wave lithotripsy at 60 or 120 shocks per minute: A randomized, double-blinded trial

Abstract

Rate of shock wave administration is a factor in the per-shock efficiency of SWL. Decreasing shock wave frequency from 120 shocks per minute (s/m) may improve stone fragmentation. This study is the first to test this hypothesis in vivo. Patients with previously untreated radio-opaque kidney stones were randomized to SWL at 60 or 120 s/m and followed at 2 weeks and 3 months. Primary outcome was success rate, defined as stone-free or asymptomatic fragments 5 mm in size 3 months post-treatment. 111 patients were randomized to 60 s/m and 109 to 120 s/m. The groups were comparable on age, gender, BMI, stent status, and initial stone area. Success rate was higher for 60 s/m (75% versus 61%, p=0.027). Patients with stone area 100 mm2 experienced the greatest benefit: success rates were 71% for 60 s/m versus 32% (p=0.002), and stone-free rates were 60% versus 28% (p=0.015). Repeat SWL treatment was required in 32% treated at 120 s/m versus 18% (p=0.018). Fewer shocks were required (2423 versus 2906, p=0.001), but treatment time was longer (40.6 versus 24.2 minutes, p=0.001). SWL treatment at 60 s/m yields better outcomes than 120 s/m, particularly for stones 100 mm2.