Effect of Stepwise Voltage Escalation on Treatment Outcomes following Extracorporeal Shock Wave Lithotripsy of Renal Calculi: A Prospective Randomized Study.

Abstract

In this study we assessed the effects of a ramping protocol in patients undergoing extracorporeal shock wave lithotripsy of renal stones. In this prospective study patients with renal stones were randomized to receive shock wave lithotripsy delivered using a ramping protocol in group 1 (first 1,000 shocks at energy level 5 followed by 1,000 shocks at energy level 6 and 1,000 final shocks at energy level 7) and a fixed voltage protocol in group 2 (all 3,000 shocks at energy level 7). Treatment was administered using a Modulith® SLX-F2. The primary outcome was treatment success 12 weeks after a single shock wave lithotripsy session, defined as lack of a stone or a less than 4 mm stone fragment on computerized tomography. Other outcomes included the stone-free rate and the perinephric hematoma incidence. A total of 300 patients (150 per group) were recruited between February 2016 and June 2018. The 2 groups did not differ in baseline parameters. Group 1 received 14.8% lower energy than group 2, which was significant (p <0.001). The treatment success rate in groups 1 and 2 was 67.8% and 73.6%, respectively, which did not statistically differ (group 1 crude OR 0.753, 95% CI 0.456-1.244, p=0.268). The stone-free rate in groups 1 and 2 was 36.6% and 41.9%, respectively, which did not differ statistically between the groups. However, in groups 1 and 2 perinephric hematoma developed in 23.8% and 43.8% of patients, respectively, which was a statistically significant difference (p <0.001). The fixed voltage shock wave lithotripsy and ramping protocols provided similar treatment success rates for renal stones. However, the ramping protocol reduced the incidence of perinephric hematoma after shock wave lithotripsy.