Harbor seal aided by noninvasive kidney stone treatment

Burst wave lithotripsy in development in human and veterinary medicine

Updated June 23, 2022

Hermes, a 23-year-old harbor seal at the Vancouver Aquarium in British Columbia, clearly had abdominal pain.

Aquarium staff noticed he was spending more time floating in the water or hunched over. He was eating less, and he appeared to be straining to urinate. Ultrasound confirmed he had kidney stones on both sides, a common but difficult-to-treat problem in seals because of their complex kidney structure.

Dr. Martin Haulena, head veterinarian and director of animal health at the aquarium, said that, in two hours while Hermes was under anesthesia, the seal underwent two procedures: an unsuccessful attempt to remove stones from one kidney through fluoroscope-guided endoscopy and, on the other kidney, a noninvasive technique known as burst wave lithotripsy, which uses focused ultrasound pulses to pulverize the stones.

Dr. Martin Haulena and team work on Hermes
Hermes, a 23-year-old harbor seal from the Vancouver Aquarium, underwent a noninvasive treatment that used ultrasound pulses to fragment many of his kidney stones. The technology is in development in human and veterinary medicine. (Courtesy of the Vancouver Aquarium)

Vancouver Aquarium veterinarians worked with urologists from Vancouver General Hospital to perform the procedures inside facilities of the University of British Columbia Centre for Comparative Medicine. The device used for the burst wave lithotripsy, a SonoMotion Break Wave system, is being studied in clinical trials in human patients. The device uses ultrasound imaging to guide delivery of the ultrasound pulses.

Dr. Haulena said Hermes had many stones greater than 1 centimeter in diameter and some greater than 2 centimeters in diameter, and the burst wave lithotripsy broke many of those stones into fragments of 1 millimeter or less.

Hermes had a few days of cramping and abdominal discomfort after the operation, likely because he was passing the broken fragments, Dr. Haulena said. But Hermes since has looked great.

“It’s definitely a procedure that we’ll need to repeat on him to try to get through all of the stones,” Dr. Haulena said. “It takes some time to break up each stone, that’s for sure.”

The technology is in development in human and veterinary medicine.

Promising results

Researchers at the University of Washington’s Applied Physics Laboratory have pioneered burst wave lithotripsy as a successor to shock wave lithotripsy, a similar procedure that is used to break up kidney stones in human patients but is successful only about 60% of the time, APL information states.

Doug Corl, PhD, chief technology officer for SonoMotion, said his company has used its own versions of the new technology to treat more than 40 human patients in the U.S. and Canada, with good results. He also noted that researchers from the University of Washington have published results from separate clinical trials with a similar device on human patients.

Dr. Eva Furrow, associate professor in the Department of Clinical Veterinary Sciences at the University of Minnesota College of Veterinary Medicine, is working with researchers at the APL and leading a clinical trial of a device designed to break up ureteral stones in cats via burst wave lithotripsy. She said her team’s early tests showed the machine could fragment calcium oxalate stones from cats in a water bath in 10-50 minutes.

Dr. Furrow’s team plans to start testing the device on up to three cats that have kidney stones and make sure the treatment does not result in any major complications, she said. A second phase would involve treating seven cats.

The initial tests are funded by the EveryCat Health Foundation, formerly the Winn Feline Foundation, and the second phase would be funded by the Focused Ultrasound Foundation.

Dr. Jody Lulich, director of the University of Minnesota Urolith Center and a member of the research team, said in a message that the device delivers focused ultrasound in short bursts at high rates and low peak pressures, and delivery is safer and more tolerable than typical shock wave lithotripsy.

Life-saving potential

If the new technology works, Dr. Furrow said, it could save many cats’ lives.

Only about 15% of cats will pass stones with the help of intravenous fluids and medications, Dr. Furrow said. Surgery can be cost prohibitive, and artificial ureters—subcutaneous ureteral bypass devices—need to be flushed and cleaned. They, too, can become lodged with minerals, she said.

Dr. Furrow said it would be a dream come true if the burst wave lithotripsy works in cats, and she hopes it someday becomes widely available to veterinarians. Much depends on those first few cases, she said.

Dr. Corl of SonoMotion said that, while his company remains focused on developing a device for human medicine, he has had conversations with many people who were excited to learn about Hermes’ treatment. He also sees potential that the cat-focused research out of the Minnesota-Washington collaboration, for example, could help develop the technology for other animal species.

Dr. Haulena at the Vancouver Aquarium said the technology could be particularly helpful in treating animals with complicated kidney anatomy, including cetaceans, pinnipeds, cattle, and certain desert animals.

“It’s a bit of a game changer, especially for animals who don’t have that typical morphology for their kidneys,” he said.

A version of this article appears in the August 2022 print issue of JAVMA.