A new technique combining two types of focused ultrasound waves offers a promising approach for treatment of urinary stones located in the ureter, according to a feasibility study in The Journal of Urology®, an Official Journal of the American Urological Association (AUA). The journal is published in the Lippincott portfolio by Wolters Kluwer.
The combined ultrasound technique can be used to reposition and break up ureteral stones – with minimal pain and without the need for anesthesia, reports the new paper by M. Kennedy Hall, MD, MHS, of University of Washington, Seattle, and colleagues. The study was funded by the NIDDK and NASA.
Potential for definitive treatment of ureteral stones, without anesthesia
Stones in the ureter, which leads from the kidney to the bladder, can cause severe pain and are a common reason for emergency department visits. Most patients with ureteral stones are advised to wait to see if the stone will pass on its own. However, this observation period can last for weeks, with nearly one-fourth of patients eventually requiring surgery.
Dr. Hall and colleagues evaluated the new technique to meet the need for “nonsurgical definitive management” of ureteral stones. The clinic-based ultrasound system incorporates two technologies: ultrasonic propulsion, with the goal of repositioning the stones; and burst wave lithotripsy (BWL), used to break up or dislodge stones.
“Ultrasonic propulsion pulses have longer duration and lower amplitude than BWL pulses,” the researchers write. The two types of energy are delivered using the same handheld probe, with real-time ultrasound imaging guidance and targeting.
Patients with ultrasonic propulsion
The investigational treatment was performed in 29 patients with ureteral stones: 16 patients were treated with ultrasonic propulsion alone and 13 with BWL bursts. Patients were recruited from the emergency department or clinic. The study was designed to test the feasibility of using the ultrasonic propulsion to reposition ureteral stones. It was also the first study to evaluate the use of BWL to break up stones in awake, unanesthetized patients.
In 19 of 29 patients, movement of the stone by ultrasonic propulsion bursts was directly observed on ultrasound imaging. In two cases, stones were repositioned from the ureter to the bladder; one of these patients felt “immediate relief” when the stone was dislodged from the ureter.
Twenty-one patients that had stones located distally – nearer the entrance to the bladder than the kidney – and had at least 2 weeks of follow-up. In 18 of these 21 cases, the stone passed out of the body; the average time to stone passage was about 4 days. In 7 out of 13 patients, BWL bursts resulted in incidental observation of fragmentation of the stone.
Results
The combined ultrasound procedure was safe and well-tolerated by patients, with no serious adverse events. Average pain scores were significantly lower after the ultrasound procedure. Patients whose stones did not pass on their own after the ultrasound procedure proceeded to planned surgical treatment.
While the results suggest a high rate of stone passage after ultrasonic propulsion and BWL, the researchers emphasize some limitation of their preliminary study – especially the fact that it included no control treatment for comparison. Dr. Hall and colleagues conclude: “These technologies have the potential to provide an advantageous and patient-centered solution for the gap between expectant management and urologic intervention for symptomatic ureteral stones.”
The ultrasonic propulsion and BWL technologies have been licensed for commercialization to SonoMotion, Inc., which recently received FDA Breakthrough Device designation for the BWL technology.
Read “First Series Using Ultrasonic Propulsion and Burst Wave Lithotripsy to Treat Ureteral Stones“
DOI: 10.1097/JU.0000000000002864
