Yang CC. et al., 2025: A Randomized Controlled Trial of Ultrasonic Propulsion-Facilitated Clearance of Residual Renal Stone Fragments vs Observation.
Claire C Yang 1 2, Elizabeth E Keating 3, Ravi Managuli 3, Nancy Honssinger 3, Sarah K Holt 1, Alana C Desai 1
1Department of Urology, University of Washington, Seattle, Washington.
2Section of Urology, Veterans Affairs (VA) Puget Sound Health Care System, Seattle, Washington.
3Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington.
Abstract
Purpose: In patients with residual stone fragments, ultrasonic propulsion (UP) increased the fragment passage rate by 58% and reduced risk of relapse by 70% vs untreated controls with minor associated adverse events (AEs). This study presents a second, independent trial of UP to demonstrate replication of those results and effective training of a novice team of users.
Materials and methods: This was a multicenter, prospective, open-label, randomized, controlled trial. Adults with residual fragments ≤ 5 mm seen on clinical imaging at least 4 weeks post lithotripsy were enrolled. The treatment group underwent UP; the control group did not. The effectiveness end points included the proportion of subjects reporting visual observation of stone passage within 3 weeks post procedure (treatment group) or randomization (controls) and the reduction in stone burden on follow-up imaging captured within 90 days post procedure/randomization. The safety end points were AEs within 3 weeks post procedure/randomization. The Fisher exact test was used for comparison.
Results: The trial was conducted April to October 2024. Fragments remained a median of 6 months after surgery before study enrollment. Ten of 12 treated participants passed fragments vs 2 of 12 controls (P = .003). Nine of 12 treated participants saw stone burden reduction on imaging vs 1 of 11 controls (P = .003). All AEs were mild, occurring in 7 of 12 treated participants and 4 of 12 controls.
Conclusions: Consistent with the index study, UP conducted by an independent group of operators demonstrated a higher rate of fragment passage and greater reduction in stone burden after UP compared with controls, with minor associated risk.
J Urol. 2025 Mar 3: doi: 10.1097/JU.0000000000004501. Online ahead of print. PMID: 40030414
Comments 1
Extracorporeal shock wave lithotripsy is an excellent non-invasive method for stone disintegration. Unfortunately, a certain proportion of patients end up with residual fragments. In the reviewer’s opinion, residual fragments are the major shortcoming of SWL. It is not directly a failure of SWL but a consequence of anatomical circumstances that counteract easy fragment passage, usually from the lower calyces.
The application of ultrasound propulsion thereby represents a method that still non-invasively can be used for improving stone clearance.
In the present report, a randomized comparison was carried out in 24 patients, 12 treated with ultrasound propulsion and 12 without this treatment as a control group. The outcome showed excellent results for the ultrasound method:
The ultrasound pulses of 25ms were delivered with 350 kHz (pulse intensity 200 W/cm2).
The result is really promising and the new techique provides a method for improving stone-free rates without anesthesia, in an out-patient setting.
Further development of this method is what we need to improve the outcome of SWL and make SWL a non-invasive method not only for stone disintegration, but in the long term also for accomplishing non-invasive fragment and gravel clearance.
My own opinion after experience with SWL in more than 20 000 SWL treatments is that the only annoying shortcoming is the presence of residual fragments despite excellent disintegration. If that obstacle can be eliminated SWL will again be a major competitor to endourological surgery. I am eagerly waiting for additional data on ultrasound propulsion as a method for stone clearance.
Hans-Göran Tiselius