The Minnesota Urolith Center processes more urinary stones than any other veterinary center in the world––they analyzed stones from around 93,000 animals last year.

That position gives the University of Minnesota (UMN) College of Veterinary Medicine (CVM) center a unique ability to make discoveries that allow veterinarians around the world to better prevent urinary stones in their patients.

Sometimes, it starts with recognizing a subtle trend.

A few years ago, the Minnesota Urolith Center received a couple abnormal stones. The center employs a technique called infrared spectroscopy, which shoots an invisible light beam through the urinary stone. This produces a “fingerprint” of the chemicals in a stone. Researchers compare those fingerprints to those of known chemicals.

Through this process, the center determined the unusual stones were formed from a naturally occurring organic compound  called choline and a food ingredient called tartrate. Since there were only two such stones in the tens of thousands the center analyzes every year, the team didn’t think much of it.

“Then, all of the sudden, we were seeing more and more,” says Jody Lulich, DVM, PhD, co-director of the Minnesota Urolith Center.

Outside veterinarians were asking University of Minnesota specialists how they could prevent the new stones. Dr. Lulich and his team knew what was likely the source of the trend, and tested their theory by collecting information on the diet of each dog who formed the newly discovered stones, called calcium tartrate tetrahydrate (CTT) uroliths.

Dogs get choline bitartrate, the main compound in CTT uroliths, from fresh dog food and through supplements recommended for dogs that eat homemade food, to ensure they’re being fed a balanced diet. Fresh dog food companies have gained popularity in the last few years, as more owners make the switch from dry food. That trend appears to be having unintended consequences for some dogs, Dr. Lulich says.

“Choline bitartrate is generally in fresh food diets that are minimally processed,” he says.

CTT urinary stones have also been reported in people who take muscle-building supplements that contain tartrate. To determine what was causing these unusual stones to form in dogs, Dr. Lulich and his team analyzed 33 uroliths, which were more common in smaller breeds and in male dogs. Using information about each dog’s diet, the researchers were able to determine what type of choline bitartrate was in the food they were eating. The data shows a likely cause between choline bitartrate found in certain diet formulations produced by some fresh dog food companies and the newly discovered CTT uroliths. The discovery was published in April in the Journal of Veterinary Internal Medicine.

Because some brands would not disclose what type of choline bitartrate they used, it’s still not clear exactly which types may put dogs more at risk for CTT uroliths. But because the new discovery found both a new type of stone and its suspected cause, Dr. Lulich says CTT uroliths will likely be very preventable. It’s also possible that if the link is confirmed, brands will change the type of choline bitartrate they use in their fresh dog food.

“We hope that we can easily prevent it, that would be the goal, because we have identified a link that is a likely cause,” Dr. Lulich says. 

References:

Jody Lulich, Lori Koehler, Lisa Ulrich, Eva Furrow (2025). Association of Diet and Calcium Tartrate Tetrahydrate Uroliths in Dogs. Journal of Veterinary Internal Medicine, Volume 39, Issue 3.