Effect of escalating versus fixed voltage treatment on stone comminution and renal injury during extracorporeal shock wave lithotripsy: a prospective randomized trial.

PURPOSE: ESWL is a minimally invasive, efficacious therapy for most renal stones. However, an optimal voltage treatment protocol ensuring effective stone comminution while minimizing tissue injury is not well established. We performed a prospective, randomized trial of the stone-free rate and renoprotective effect of an escalating vs a fixed voltage treatment strategy during ESWL.

MATERIALS AND METHODS: Between February 2006 and June 2008 we enrolled 45 patients undergoing ESWL for a renal stone in this institutional review board approved trial. A Dornier DoLi 50 lithotriptor was used. Patients were randomized to receive the escalating strategy of 500 shocks at 14k V, 1,000 at 16 kV and 1,000 at 18 kV or the fixed strategy of 2,500 shocks at 18 kV. Abdominal x-ray was done to determine the stone-free rate at 1 month. Voided urine was analyzed for beta2-microglobulin and microalbumin before, immediately after and 1 week after ESWL to evaluate renal damage.

RESULTS: Median patient age was 48 years. Median stone size was 8 mm. Of patients in the escalating group 81% were stone-free vs 48% in the fixed group (p <0.03). There was a significant difference between microalbumin and beta2-microglobulin 1 week after the procedure (p = 0.046 vs 0.045). There was trend toward a difference in microalbumin and beta2-microglobulin immediately after the procedure (p = 0.17 and 0.25, respectively).

CONCLUSIONS: This prospective, randomized study shows that an escalating voltage treatment strategy produces better stone comminution than a fixed strategy. The study suggests that there may be a protective effect against damage caused by ESWL with an escalating treatment strategy.