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Bladder stones form when minerals in urine clump together into a mineralized mass — veterinarians call this a urolith. In dogs, the two most common types of bladder stones in dogs are struvite stones and calcium oxalate stones. Read on to learn must-know information about these stones and about bladder stones in dogs more generally.
Signs of Bladder Stones in Dogs
Dogs with bladder stones may display signs associated with a lower urinary tract disease, or they might not show any signs at all. Signs that your dog may have a bladder stone include:
- Straining to urinate
- Bloody or discolored urine
- Pungent urine
- Needing to urinate more often than usual
- Having accidents in the house
- Licking their genital area more than usual
- Having lower energy or a reduced appetite
Bladder Stone Diagnosis
Vets can identify most bladder stones in dogs through an X-ray or abdominal ultrasound. Your vet will likely also want to submit urine for analysis and culture for bacteria. Because tumors and infections may cause the same clinical signs as bladder stones, it's important to follow all your vet's testing recommendations.
What Are Struvite Stones in Dogs?
Struvite stones are one of the most common types of bladder stones in dogs. Struvite is a hard mineral deposit that forms in urine when magnesium and phosphate stick together. On their own, struvite crystals in urine are relatively common and may not be a problem. In dogs, struvite stones usually form in urine that's been infected with ammonium-producing bacteria. This raises the urine pH, causing the struvite crystals to clump together to form a stone.
According to the Veterinary Information Network, 85% of dogs with struvite stones are female and the average age of an affected dog is 2.9 years old.
Shih tzus, miniature schnauzers, Yorkshire terrier, Labrador retrievers and dachshunds appear to be at an increased risk of forming struvite stones. In dogs, these stones are also most often associated with a lower urinary tract infection.
Treatment for Struvite Stones
According the American College of Veterinary Internal Medicine (ACVIM), your vet will likely suggest nutritional dissolution of the struvite stones — in other words, they will recommend feeding a food that is formulated to help these stones dissolve. Be sure to ask your veterinarian if a therapeutic food such as Hill's Prescription Diet is a good option for your dog. If the stone is associated with a urinary tract infection, your vet may also prescribe antibiotics.
One possible theory that your vet may recommend is a procedure called lithotripsy, a procedure that uses sound waves to break up the stones.
The last possible form of treatment is through surgical removal of the stones. Because it is much more invasive, this should often be the last course of treatment unless there is a high risk of urinary obstruction that could put your dog's health in danger in the immediate future.
What Are Calcium Oxalate Stones in Dogs?
While a higher urine pH aids the formation of struvite stones, the pH of your dog's urine has less of an effect on the formation of calcium oxalate stones. Instead, calcium oxalate stones form when urine is supersaturated with calcium and oxalate.
According to a study in The Canadian Veterinary Journal, calcium oxalate stones — in contrast to struvite stones — are more common in male dogs than female dogs. Older dogs are also more likely to be affected. Per the Canadian Veterinary Journal study, the average dog with calcium oxalate stones was 9.3 years old. And, while most breeds can be affected, Keeshonds, Norwich terriers, Norfolk terriers and Pomeranians are at increased risk. Recently a genetic defect that predisposes dogs to calcium oxalate was identified by the University of Minnesota and a genetic test is available for English bulldogs. They have also identified the mutation in the American Staffordshire terrier, border collie, Boston terrier, bullmastiff, Havanese, rottweiler, and Staffordshire bull terrier.
Calcium oxalate stones can form in sterile urine and aren't usually associated with a lower urinary tract infection.
Treatment for Calcium Oxalate Stones
Unlike struvite stones, calcium oxalate stones can't be dissolved using nutrition. Instead, they can be removed via surgery, or the non-surgical procedures lithotripsy or voiding urohydropropulsion. It's always a good idea to submit stones for analysis, as some dogs can form multiple types of bladder stones at the same time.
The Role of Nutrition in Treating and Helping to Prevent Bladder Stones
Once the stones are out of your dog's urinary system, nutrition and water consumption play an important role in preventing them from coming back.
Because crystals and stones are less likely to form in dilute urine, it's crucial to both increase the amount of water that your dog drinks and feed a food that decreases the amount of mineral in your dogs urine. You can increase your pup's water intake by moistening their food with water, feeding them canned food, flavoring their water with low sodium chicken or beef broth or putting their water in a dog water fountain.
In addition to these, you can also feed your dog food that's specially formulated to help reduce the risk of stone formation. For example, Hill's Prescription Diet has complete and balanced therapeutic dog foods that provide high-quality nutrition while reducing the risk of calcium oxalate and struvite crystal formation by reducing the amount of minerals in your dogs urine. Foods that help reduce the risk of bladder stones come in both canned and dry forms.
Even if your dog develops bladder stones, there are steps you can take to help reduce the risk of them recurring or extend the time between recurrences. Your vet may recommend an X-ray to monitor your dog once or twice a year so that if new stones form, they can be removed through non-surgical means. You and your veterinarian will work together as a team to determine the best ways to manage and monitor your dog.
Also consider checking out the University of Minnesota's Urolith Center for additional potential treatment options. If you have any questions or concerns about bladder stones in your dog, don't hesitate to ask your veterinarian for advice — they're your best resource for advice about your pet's health!
Sarah J. Wooten, DVM, CVJ
A graduate of UC Davis School of Veterinary Medicine, Dr. Wooten is a small animal veterinarian with 16 years experience. She lives with her human and fur family in Greeley, Colorado.