Rapha, a 6-year-old Rhodesian ridgeback, has two speeds: chasing the wild turkeys and squirrels that roam his Southwest Minneapolis neighborhood, and sleeping, preferably on the sofa that he isn’t supposed to be on. He doesn’t play fetch but loves to chew on sticks.

In other words: “He's a traditional Rhodesian,” says Adam NaPier, Rapha’s owner.

Rapha represents his breed in another way, by contributing to a discovery made by researchers in the College of Veterinary Medicine’s (CVM) Minnesota Urolith Center. The center tests urinary stones from animals around the world, including dogs like Rapha. The center has been providing the service free of charge since it opened in 1981.

“The reason we have kept it free over the years is because knowing what the stone type is can have such an impact on how you manage and prevent them from forming again,” says Eva Furrow, co-director of the Minnesota Urolith Center. “We want to have this resource be as accessible as possible to veterinarians and to pet owners.”

NaPier had a house full of visiting family when Rapha started having accidents indoors, something he hadn’t done since he was a puppy. When he went into the backyard, he seemed to be in pain.

Rapha was rushed to his primary vet in St. Louis Park, where he was treated for a urinary tract infection (UTI). The antibiotics seemed to be helping, but then he had another accident. An X-ray revealed a cluster of urinary stones in his bladder and urethra.

“There were too many to count,” NaPeir says.

Rapha underwent surgery, but some of the stones were lodged tightly in his urethra and could not be removed. It was then that his veterinarian suggested Rapha go to the University of Minnesota Veterinary Medical Center (VMC).

At the VMC, Rapha had a procedure called laser lithotripsy, which uses waves of energy to break up urinary stones, also called uroliths. Furrow and one of her trainees performed his procedure.

While Furrow manages dogs with stones weekly, Rapha stood out and prompted her to take a closer look.

“It’s rare to find stones in this breed,” says Furrow, who is also an associate professor of small animal internal medicine at CVM and a founder of the newly formed American College of Veterinary Nephrology and Urology.

While the Minnesota Urolith Center analyzes nearly 70,000 stones from dogs each year, only a dozen come from Rhodesian ridgebacks.

To uncover the cause of Rapha’s stones, researchers at the Minnesota Urolith Center cracked them open so they could get a closer look at the layers that formed the stone.

“Knowing what is at the center of the stone is important because that’s usually the catalyst of why the stone formed,” Furrow says. “But every layer tells us something about what caused the stone."

The center’s team looked at the cracked sample under a microscope, blotting it with different oils that would make the sample disappear when the substance was a match.

The test revealed that Rapha’s stones were pure calcium oxalate throughout the layers.

Related breeds held some clues that prompted further testing.

“Rhodesian ridgebacks fall close to the group of dogs that include bulldogs, mastiffs, and American Staffordshire terriers, and in those breeds, we discovered a genetic disorder that causes calcium oxalate stones,” Furrow says. A blood test confirmed Furrow’s suspicion that Rapha had a genetic disorder that made him more susceptible to forming this type of stone.

Rapha’s case was the smoking gun that led to Rhodesian ridgebacks being added to the list of breeds that form calcium oxalate stones from a specific genetic disorder. Now, other veterinarians can use the information gleaned from Rapha’s case to better treat other Rhodesian ridgebacks who form this stone type.

“We know that the risk for recurrence is high, but based on the protein involved, we can make recommendations about diet, medication, and other strategies to decrease stone formation for dogs with this disorder,” Furrow says.

Furrow and the Minnesota Urolith Center team are continuing to chip away at understanding why dogs, and other animals, form stones.