High-energy v low-energy shockwave lithotripsy in treatment of ureteral calculi

The size of the crater formed in a urinary calculus subjected to shockwave lithotripsy (SWL) is directly proportional to the energy delivered to the stone surface. This study compared the effect of high and low energy levels on the outcomes of ureteral SWL. Ureteral calculi (N = 336) were treated with the conventional low-energy Siemens Lithostar and 62 with the higher-energy (1.02 v 0.5 mJ/mm2) modification of the Lithostar, the Siemens Shock Tube C. Stone locations included all regions of the ureter. The average stone treated with the standard Lithostar measured 8.1 mm in diameter and received 5461 shockwaves (treatment time 45 minutes) at 17.2 kV (range 14.5-19.0 kV). The stone-free rate was 72%, with stents being used in 16% of patients and a retreatment rate of 9%. The typical stone treated with Shock Tube C was 10.4 mm in diameter and received 3528 shockwaves (treatment time 30 minutes) at an average energy setting of 4.1 (range 1.5-8.0). The stone-free rate was 75%, with stents being used in 9.8% of cases, and a retreatment rate of only 1.6% (P < 0.003). In this study, Shock Tube C yielded stone-free rates equivalent to those of the conventional machine. However, the number of shockwaves, treatment time, and retreatment rate were significantly lower with the new shock tube. High-energy lithotripsy is more efficient than low-energy treatment of ureteral calculi.