Low-Intensity Ultrasound Breaks Up Kidney Stones with 70% Success Rate in SOUND Trial

A New Chapter in Kidney Stone Treatment

For the millions of people who have experienced the searing pain of a kidney stone, the prospect of a gentler, office-based treatment that avoids the need for general anesthesia or a hospital visit is genuinely life-changing. New data from the SOUND trial, presented in Washington, suggests that low-intensity ultrasound technology may deliver exactly that. Researchers reported that the Break Wave lithotripsy device successfully shattered kidney stones in 70% of treated patients, using low-pressure ultrasound waves that can be administered during a routine office visit. The findings signal a potential shift in how urologists approach one of the most common and painful conditions in medicine — one that affects roughly one in ten people at some point in their lives.

What Was Known Before the SOUND Trial

Kidney stone treatment has long been dominated by a handful of options, each with meaningful trade-offs. Extracorporeal shock wave lithotripsy (ESWL), introduced in the 1980s, uses high-energy shock waves generated outside the body to pulverize stones into sand-like particles that can be passed naturally in urine. While effective, traditional ESWL typically requires sedation or anesthesia, is performed in a hospital or surgical center, and can cause significant discomfort during and after the procedure. The high-energy waves can also damage surrounding kidney tissue and blood vessels, leading to bruising and, in rare cases, more serious complications such as bleeding or hypertension.

Ureteroscopy — threading a thin scope through the urethra and bladder up to the stone — offers high success rates but is invasive and requires anesthesia. For larger stones, percutaneous nephrolithotomy involves a small incision in the back, which is even more invasive. Meanwhile, medical expulsive therapy using alpha-blockers like tamsulosin has shown only modest benefits for smaller stones. Against this backdrop, researchers have been searching for a truly non-invasive, low-risk treatment that can be delivered without the logistical and physical burdens of current options. Low-intensity ultrasound technology has been explored in laboratory and early clinical settings for years, but robust trial data in human patients has been limited — until now.

Inside the Evidence: The SOUND Trial Findings

The SOUND trial evaluated the Break Wave lithotripsy device, a technology that uses low-pressure ultrasound pulses — fundamentally different from the high-energy shock waves used in conventional ESWL. Unlike traditional lithotripsy, which relies on a single powerful shock to fracture stones through compressive and tensile forces, low-intensity ultrasound uses sustained, gentle wave energy to create cavitation bubbles that gradually erode and fragment the stone from the surface inward. This mechanism is designed to minimize collateral tissue damage while still achieving meaningful stone breakdown.

The findings, presented at a major medical conference in Washington, showed that 70% of patients treated with the device achieved successful stone fragmentation. The procedure was performed in an office setting, meaning patients avoided the need for anesthesia, an operating room, or an extended recovery period. The researchers also reported that the treatment was safe, with no serious adverse events attributed to the device during the study period. However, several important methodological details were not fully reported in the initial presentation summary. The researchers did not disclose the total sample size, the specific stone sizes or locations targeted, the exact follow-up duration, or detailed statistical measures such as confidence intervals. These omissions are common in conference presentations, where time constraints limit the depth of data shared, and full publication in a peer-reviewed journal typically follows months later. The name of the lead author and the affiliated institution were also not specified in the available summary.

What the available data do make clear is that the 70% fragmentation rate represents a clinically meaningful outcome for a treatment that prioritizes patient comfort and accessibility. For context, traditional ESWL success rates vary widely — from roughly 50% to 90% — depending on stone size, composition, location, and the specific technology used. The SOUND trial’s results place low-intensity ultrasound within a competitive range, particularly given the advantages of an office-based, anesthesia-free approach.

What This Means for You

If you are one of the roughly 600,000 Americans who develop kidney stones each year, the emergence of low-intensity ultrasound technology could meaningfully expand your treatment options in the near future. The most immediate implication is the possibility of receiving stone-breaking treatment during a routine urology appointment — no IV line, no sedation, no recovery room, and no need to arrange a ride home. For patients with smaller or moderately sized stones who are not good candidates for surgery or who wish to avoid more invasive procedures, this approach could fill an important gap in care.

It is important to keep expectations measured, however. The SOUND trial data have not yet been published in a peer-reviewed journal, meaning the full methodology and results have not undergone the rigorous scrutiny that typically precedes clinical adoption. Additionally, the 70% success rate — while promising — means that roughly three in ten patients did not achieve adequate stone fragmentation, and it remains unclear what factors predicted success or failure. Patients should discuss all available options with a urologist, including watchful waiting for small stones, medication to aid passage, ESWL, ureteroscopy, and now, potentially, low-intensity ultrasound as it becomes more widely available.

Expert Perspective and Caveats

While the SOUND trial results are encouraging, urologists who were not involved in the study caution that conference presentations represent an early stage of evidence dissemination. Without a full peer-reviewed manuscript, key questions remain unanswered: How did the device perform across different stone types, particularly hard calcium oxalate monohydrate stones that resist fragmentation? What was the stone-free rate at 30 or 90 days — a more stringent endpoint than simple fragmentation? Were any patients crossed over to other treatments? And how does the total cost of an office-based ultrasound procedure compare with existing options from a payer and patient perspective? These questions will need to be addressed before low-intensity ultrasound can be widely endorsed in clinical practice guidelines. Nonetheless, the technology represents a genuine innovation in a field that has seen relatively few breakthrough advances in recent decades, and the safety profile reported thus far is highly encouraging.

Frequently Asked Questions

Q: How does low-intensity ultrasound differ from traditional shock wave lithotripsy?

Traditional shock wave lithotripsy uses a single high-energy acoustic pulse that creates compressive and tensile forces to fracture a stone abruptly. Low-intensity ultrasound, by contrast, uses continuous lower-energy waves that generate cavitation — the formation and collapse of tiny bubbles on the stone’s surface — which gradually erodes the stone. The lower energy level is what makes the procedure comfortable enough to perform without anesthesia in an office setting, and it is believed to cause less damage to surrounding kidney tissue.

Q: Is the Break Wave device currently available to patients?

As of the time of the SOUND trial presentation, the Break Wave lithotripsy device is still investigational. The data presented at the Washington conference represent clinical trial results, not a commercial launch. Patients interested in the technology should ask their urologist about clinical trial opportunities or watch for regulatory clearance updates, which typically follow successful pivotal trial results by one to three years depending on the jurisdiction.

Q: What types of kidney stones can be treated with low-intensity ultrasound?

The available SOUND trial summary did not specify which stone types were included or whether the 70% success rate varied by stone composition. In general, calcium oxalate stones — the most common type — can be resistant to certain forms of lithotripsy, while uric acid and struvite stones tend to be more friable. Full details on stone composition and how it affected outcomes will likely emerge when the study is published in a peer-reviewed journal. Patients should note that stone type is often unknown until fragments are analyzed after passage or removal.

Q: Does the procedure hurt, and what is recovery like?

According to the SOUND trial investigators, the low-intensity ultrasound procedure was performed in an office setting without anesthesia, which strongly suggests that patients tolerated it well without significant pain. This contrasts with traditional ESWL, which often causes discomfort requiring sedation. Because the technology is designed to minimize tissue trauma, recovery is expected to be minimal, with patients likely able to resume normal activities immediately after the appointment. However, some patients may still experience mild soreness or blood in the urine as stone fragments pass in the days following treatment.

Q: How soon might this become a standard treatment option?

The timeline from successful clinical trial results to widespread clinical availability typically spans several years. After the SOUND trial data are fully published in a peer-reviewed journal, the device manufacturer would need to seek regulatory clearance — in the United States, this means FDA review, which can take six to eighteen months depending on the classification pathway. Following clearance, adoption depends on urology practices acquiring the equipment, insurers establishing coverage policies, and professional societies updating clinical guidelines. Realistically, patients may begin seeing this technology in select academic centers and large urology groups within two to four years, assuming the full published results support the early findings.

Sources

• MedPage Today (2025). Low-Intensity Ultrasound Shatters Kidney Stones in 70% of SOUND Trial Patients. Conference report from Washington. https://www.medpagetoday.com