Ultrasound-based technologies demonstrate efficacy for kidney stones

Ultrasound-derived technologies show promise to safety and effectively treat kidney stones, according to research presented at the 2024 American Urological Association Annual Meeting in San Antonio, Texas.¹

Mathew D. Sorensen, MD, MS, FACS

Describing the background for the research, Mathew D. Sorensen, MD, MS, FACS, explained, “Our contemporary management of kidney stones, I would say, for most of us that do this regularly is that we tend to observe small renal stones 5 mm or [smaller]. We oftentimes try to avoid surgeries in those patients, because their likelihood of successfully passing [the stone], though usually with symptoms, is usually quite good. And then we discuss elective treatment of these stones as they get bigger with either shock wave lithotripsy or ureteroscopy.

“We also will encounter patients that are in the process of trying to pass a stone. If they're doing well, we will give them…up to 6 weeks to try to pass their stone, with the hope being…that we can avoid surgery. Despite the fact that we know that residual fragments after our treatments tend to cause trouble in up to 20% to 40% of patients afterwards, we still would have the standard, unless the rest of the fragments are quite large, to observe these and to give them the chance to try to pass on their own.

“My take-home from this is that our current management strategies are really aimed at trying to prevent surgeries. We're really trying to avoid having these patients go through the burden of anesthesia, instrumentation…We're not really trying to prevent emergency department visits or painful events. We have 2 technologies that we hope will change that paradigm,” said Sorensen, an associate professor of urology at the University of Washington, Seattle and director of the Comprehensive Metabolic Stone Clinic at the Puget Sound VA.

The first of these technologies, ultrasonic propulsion of stones, has been in development for approximately 10 years, Sorensen said.

“It uses focused ultrasound that's applied to the skin transcutaneously, and then we sweep the fragments with real-time ultrasound out of, typically, the lower pole of the kidney and encourage them to move towards the ureter,” Sorensen explained.

He and his co-investigators recently completed a randomized clinical trial that included 84 patients who received imaging 90 to 100 days after ureteroscopy or shock wave lithotripsy. Patients were randomly assigned to receive propulsion treatment or control. Outcomes included surgery, symptomatic unscheduled emergency department/clinic visits, or stone growth due to residual fragments, as well as fragment passage within 21 days and any adverse events within 90 days. The outcomes were assessed by CT scan within approximately 90 days after and were followed annually up to 5 years.

The investigators found that the propulsion group had a 70% lower risk of relapse than the control group (HR 0.30, 95% CI: 0.13-0.68). There was also a 52% longer time to relapse with the propulsion group—4.2 years vs 2.8 years (P < .003).

“The propulsion procedure appears to reduce the risk of relapse, is well tolerated, and [is delivered] in an office-based setting and does not require any sort of medications,” Sorensen said.

The second technology, burst wave lithotripsy, utilizes focused ultrasonic lithotripsy to fracture stones. It uses real-time ultrasound guidance and can be used to treat stones in the kidney and the ureter. The company SonoMotion is working to commercialize this technology and has been given an FDA breakthrough therapy designation.

“The goal would be that, ultimately, when this technology reaches the bedside, that we can use the technology in awake patients, in the office, with no anesthesia, and we would treat kidney stones that might we otherwise observe,” Sorensen said.

The therapy probe is custom designed by SonoMotion and is used with a GE ultrasound platform.

Sorensen summarized 2 studies evaluating break wave lithotripsy. The first is evaluating break wave lithotripsy and propulsion in patients with small (2 mm-7 mm) asymptomatic renal stones. The goal of the study is to reduce future stone events. The study is currently in the initial feasibility phase, in which the investigators are recruiting approximately 20 patients “that will then inform our 100-patient randomized control trial,” said Sorensen. The cohort will include a subset of patients with spinal cord injury.

Preliminary results of this study included 15 patients and 23 stones, with an average size of 4.8±1.4 mm. Eleven patients completed the 90-day CT follow-up. Five patients were stone free, and significant stone volume reduction was observed. Adverse events were reported to be mild and self limited.

The second study, which was recently completed, evaluated stones in patients headed for surgery (< 10 mm in size). Patients underwent 30 minutes of break wave lithotripsy treatment. The study’s goal was to assess anesthesia needs and stone fracturing. The prospective, single-arm, multicenter clinical trial include 44 subjects in 5 centers in the US and Canada.

In the study, 22 procedures (50%) required no medication, 16 (36%) required mild anesthesia, 2 (5%) required conscious sedation, and 4 (9%) required general anesthesia. In addition, 86% of patients did not receive sedation.

REFERENCE

1. Sorensen MD. Paradigm-shifting, practice-changing clinical trials in urology: office-based removal of small urinary stones. Presented at: 2024 American Urological Association Annual Meeting. May 3-6, San Antonio, Texas