Fragmentation and Facilitated Clearance of Small, Asymptomatic, Renal Stones with Burst Wave Lithotripsy and Ultrasonic Propulsion: A 14-Month Follow-Up

PURPOSE:To evaluate if treating small asymptomatic renal stones with office-based burst wave lithotripsy (BWL) and ultrasonic propulsion (UP) prevents future stone growth, emergency department visits, and surgical procedures for stone care. METHODS:Participants with 2-7 mm asymptomatic renal stones were treated with BWL to break stones and UP to facilitate clearance of fragments. The primary outcome measure was relapse, defined as stone growth, an urgent or emergent medical visit, or operation for the randomized stones of interest within 14 months of the procedure. These events would include visits caused by the treatment and the presence of residual stones. Relapse data from untreated control groups with small stones or fragments from three published contemporaneous studies with similar protocols and 1- to 5-year follow-up were pooled and inverse probability weighted for comparison. The cumulative incidence of relapse was estimated using the Kaplan-Meier method. RESULTS:Between April 2023 and September 2024, 18 participants underwent treatment of 27 asymptomatic small stones; 7 (39%) participants underwent a second BWL procedure to complete treatment. The control group had significantly shorter time to relapse than the treatment group (p = 0.048 by weighted log-rank test). The hazard ratio for relapse in the treatment group, compared with the control group, was less than 0.01 (p < 0.001). There was no relapse in the treated group within 14 months. For comparison, the 1-year relapse rate was 26% in the control group. CONCLUSIONS:In a small feasibility study, no stone-related relapse events occurred within 14 months following treatment of small, asymptomatic renal stones with BWL and UP.