Calcium oxalate crystals forming in a dog's urine can clump together and form bladder stones, or uroliths. These stones can block a dog's urethra, impeding his ability to urinate. That's a red-alert veterinary emergency, as a dog who can't pee can die within a few days—from either uremic poisoning or bladder rupture.
Hypercalciuria, the presence of too much calcium in the urine, can cause calcium oxalate crystals or stones to form. Though the cause of this is unclear, hypercalciuria results when the kidneys don't excrete enough calcium, or the dog's skeleton absorbs too much.
Although any dog can develop calcium oxalate crystals or bladder stones, it's more prevalent in certain breeds. These include the bichon frise, shih tzu, Lhasa apso, Yorkshire terrier, miniature schnauzer and miniature poodle. Males make up the overwhelming majority of dogs developing calcium oxalate crystals. Other types of crystals are more common in different breeds.
If your dog is afflicted with calcium oxalate crystals or stones, you might notice blood in his urine. He could strain to pee. If the stone causes an obstruction, your dog strains to urinate and is obviously in pain. He'll lick at his privates and might howl or whimper from the pressure.
A change in diet sometimes dissolves struvite stones. That's not the case with calcium oxalate stones. If your dog has stones in his bladder or urethra, they'll likely require surgical removal. Your vet can't tell what sort of stones are bothering your dog without a sample for analysis. If your dog suffer from stones but isn't blocked, your vet might perform a urohydropropulsion, which consists of flushing out the stones via a catheter. This works only with little stones.
Never give your dog calcium supplements without veterinary approval. Once dogs develop calcium oxalate crystals and stones, they're at greater risk of developing them again after surgical removal. To help prevent a recurrence, your vet will prescribe a diet of canned food low in sodium, protein and oxalates. Such a diet should maintain urine pH levels between 6.5 and 7.5, according to the Merck Veterinary Manual. Your vet should test your dog's urine every few months to ensure the diet helps keep urine pH within the correct range.
By Jane Meggitt
Veterinary Partner: Oxalate Bladder Stones (Canine)
VCA Animal Hospitals: Calcium Oxalate Bladder Stones in Dogs
University of Minnesota Minnesota Urolith Center: Canine Calcium Oxylate Uroliths [PDF]
petMD: Crystals in the Urine of Dogs
Merck Veterinary Manual: Urolithiasis in Small Animals
About the Author
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.