By Paula Fitzsimmons
Stones form in an animal’s urinary tract when minerals are concentrated in the urine, then crystallize. The diet you feed your companion plays a pivotal role in the treatment and prevention of stones. “What you need to do is try to alter the balance that is contributing to the high concentration of certain minerals,” says Dr. Anthony Ishak, a veterinarian with BluePearl Veterinary Partners in Tampa, Florida.
The type of stone that forms depends on which minerals are present in high concentrations. “For example, excess magnesium and phosphorus can contribute to struvite formation,” says Dr. Dan Su, a veterinary clinical nutrition resident at University of Tennessee, Knoxville. “Another, more complicated example is that while excess calcium can contribute to calcium oxalate stones, insufficient calcium leads to decreased binding of oxalate in the intestines and subsequently more oxalate excreted in urine.” In other words, both too much and too little calcium can lead to the formation of stones. Pets need just the right amount of calcium to prevent stone formation.
Diagnosing the precise type of stone afflicting your companion—and tailoring a diet to treat it—should be left to your veterinarian. The following vet-recommended tips can help you better understand your pet’s special nutritional needs—and put you in a better position to provide optimal care.
Work Closely with Your Veterinarian
Bladder stone management isn’t a one-size-fits-all model. It requires the expertise of someone who understands how food impacts stone development. Your vet is your pet’s first line of defense.
“Overall, this is not a condition that a pet owner can reliably fix by changing dog foods,” says Ishak, who is board-certified in internal medicine. “This is one problem that does call for professional help to solve most expeditiously. There are some stones that form with certain medical conditions (infections, liver problems, etc.), complicating diagnosis and management further.”
Other factors add to the complexity. “Sometimes the urine may need to become more acidic but other times it may need to become more basic,” he says. “In addition, different stones require different mineral or protein reductions.”
Mineral concentration and pH can potentially be manipulated with diet, says Dr. Jonathan Stockman, a board-certified veterinary nutritionist at the James L. Voss Veterinary Teaching Hospital at Colorado State University in Fort Collins. “However, it can be complicated when management of one type of crystal increases the risk for the formation of a different type of crystal.”
Focus on Water Intake
Keeping an animal well-hydrated is a strategy vets often recommend for keeping bladder stones in check. “Diluting the urine (and thus the concentration of minerals) by increasing water intake is typically the most critical component of dietary management, and the part that seems to be done the least,” says Dr. Cailin Heinze, a veterinarian at Cummings School of Veterinary Medicine at Tufts University in North Grafton, Massachusetts.
If your pet doesn’t readily drink water from his bowl, Stockman has advice to offer. “This may be done by feeding a high moisture diet [canned food], adding flavor to the water, increasing the number of water bowls, and some cats and dogs may like water fountains that provide running water,” he says.
Adding water to canned food and making water more enticing by using ice cubes or small amounts of flavoring, like chicken broth, are strategies recommended by Dr. Jennifer Larsen, associate professor of clinical nutrition at the University of California-Davis, School of Veterinary Medicine.
If you’re concerned about over-hydrating your pet, keep in mind that “it’s hard to give your pet too much water as long as they are voluntarily drinking,” Ishak says. “But don’t force water into a pet.”
Feed Your Companion a Therapeutic Diet
Commercial therapeutic diets are the best option for reducing the development of most types of stones, says Heinze, who is board-certified in veterinary nutrition.
“Home-cooked diets are usually a second choice for dogs that can’t eat a commercial diet, rather than the first choice for stone prevention, because they can’t undergo the kinds of testing that commercial therapeutic diets do to ensure that the urine produced has the greatest chance of reducing stone risk,” she says.
Therapeutic diets work by providing less of the substances that form the stones, Su says. “Some of these diets are designed for prevention of stones, and some for dissolution of stones (and are therefore more depleted in stone formation ingredients), so make sure the pet is monitored by a veterinarian while on these diets.”
The type of diet your vet prescribes will depend on the stone. For example, “for dogs with urate and cysteine bladder stones, your vet will recommend specific lower protein therapeutic diets that promote alkaline pH and reduce intake of stone precursors,” says Larsen, who is board-certified in veterinary nutrition.
To prevent calcium oxalate stones, the prescribed diet will likely have moderate levels of protein, calcium, and phosphorous. “And it may have increased sodium chloride (to induce dilute urine) or higher fiber,” explains Dr. Joe Bartges, professor of medicine and nutrition at the College of Veterinary Medicine at the University of Georgia in Athens.
Be Careful with Added Ingredients
A cat or dog on a therapeutic diet shouldn’t be allowed to eat other foods without the permission of your vet. Dr. Susan Jeffrey, a veterinarian with Truesdell Animal Hospital in Madison, Wisconsin, had a client who had been mixing a therapeutic diet with an over-the-counter diet. “The cat's stones returned and he needed another surgical procedure to remove them,” she recalls.
Although your vet has the final say about which foods are appropriate, there are some general guidelines. “Avoid rawhide, pig ears, bully sticks, and other collagen-rich treats,” Larsen says. “They are not only not high enough in moisture but also provide compounds converted to oxalate by the body,” which is an obvious no-no for pets with calcium oxalate stones. Su adds, “For patients with calcium oxalate stones, make sure to avoid excess calcium (avoid dairy products, extra supplementation), and high oxalate ingredients (like spinach).” Animals with urate and cysteine stones should avoid added protein (especially from seafood and organ meat for those with urate), Larsen says.
And continued, close monitoring for symptoms of stone recurrence is vital. Dietary manipulation does not work in all cases. “Recurrence of stones, especially calcium oxalates, can occur in some patients even if they are strictly fed the appropriate therapeutic diets,” Su says.
Don’t Use DIY Treatments Without Consulting a Vet
Some pet parents reach for apple cider vinegar in hopes of acidifying their companion’s urine. But this is not necessarily a good idea.
“I wouldn't add anything to increase the acidity of a diet without the supervision of a veterinarian,” says Jeffrey, whose professional interests include preventative care. “If the urine becomes too acidic, calcium oxalate crystals/stones can develop.”
Cranberry-based products are touted for urinary tract health. “It may help with recurrent urinary tract infections because of compounds that cranberries contain (called proanthocyanidins, a class of polyphenols found in plants),” says Bartges, who is board-certified in veterinary internal medicine and veterinary nutrition. However, cranberry juice doesn’t acidify urine, he says, so it’s not considered helpful for dissolving stones.
Running supplements past your vet is a golden rule, even more so if your pet has a bladder condition. “There are supplements that can be added to food to modify urinary pH like potassium citrate and methionine, but those should only be used as directed by a veterinarian,” Su explains.
Some supplements can actually increase the risk of stones in susceptible animals, Heinze says. “Examples include brewer’s yeast for dogs with urate stones, vitamin C or calcium for dogs with calcium oxalate stones, or products that alkalinize the urine for struvite stones.”
A specially-formulated diet is a powerful tool that can prevent and treat some types of bladder stones in cats and dogs. The wrong foods, however, have the potential to worsen your pet’s condition. Following your vet’s dietary guidelines, ensuring adequate water intake, and being mindful of added ingredients can restore your companion to optimal health.