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Trial Testing Ultrasound Technique to Move Kidney Stones

Mike Bailey

Mike Bailey (University of Washington)

A clinical trial at University of Washington in Seattle is testing an ultrasound device that moves the position of kidney stones in the body to encourage safe passage of the stones without surgery. The early-stage trial is testing the device invented in the lab of engineering professor Mike Bailey, who is also starting a company to commercialize the technology.

Kidney stones are crystalline deposits that form in the urine inside the kidney and vary in size. Smaller stones can pass without incident, causing little discomfort, while larger stones that get lodged in the urinary tract can cause intense pain. National Institute of Diabetes and Digestive and Kidney Diseases estimates kidney stones result in 1 million visits to U.S. health care providers each year, with 300,000 of those visits ending in emergency rooms.

Ultrasound is a common technique in use for 30 years for breaking up larger kidney stones into smaller pieces that can pass more easily out of the body. The technique sends short pulses of high-energy sonic waves to shatter the stone, which while not requiring surgery, may still call for a general anesthetic. Ultrasound used in this manner can also leave behind fragments, which can form later into larger stones, thus restarting the process.

Bailey and colleagues devised a technique that sends longer sonic pulses that reposition smaller stones from lower in the kidney to the middle to allow for easier passage. Patients today can achieve this state with a technique called mechanical percussion and inversion, where the body is inverted on a stretcher and a large vibrator is applied to the back over the kidney to move the stone.

The Washington technique is less physically demanding than mechanical percussion and inversion, and uses regular commercial ultrasound modified to emit longer pulse waves that are slightly stronger than waves used for pregnancy images. The ultrasound probe is applied to the patient’s lower back over the kidney, where a urologist can locate the stone, then direct the waves to move it to the middle of the kidney.

Bailey and colleagues, including urologists from University of Washington medical center, built and tested prototypes on artificial kidneys and with pigs. “We’ve had extensive testing in an animal model,” says Jonathan Harper, a urology professor and team member in a university statement. “If it acts in the same way in a human kidney, I think it’s extremely promising.”

The clinical trial is testing the technique’s safety and effectiveness with 15 kidney stone patients, who are now being recruited. The trial will measure the ability of the technique to move the stone a distance greater than two millimeters, and in a predetermined direction, using 40 ultrasound pulses over the course of an hour. The trial will also evaluate any discomfort felt by the patient as a result of the treatments, as well as adverse events recorded in the next 90 days. The study is funded by National Institutes of Health and National Space Biomedical Research Institute, since astronauts run a increased risk of developing kidney stones during space travel.

Bailey’s team is working with the university’s technology transfer office to gain patent protection for the technique. The researchers are also forming a new company, SonoMotion, to commercialize the discovery. Bailey says the researchers are collaborating with an unnamed hardware manufacturer, also in Washington State, where SonoMotion will provide the software for the product to take to market.

In the following video, Bailey and colleagues tell more about and demonstrate the ultrasound system.

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