Your pup's kidneys are filled with thousands of nephrons, each containing tubes and capillaries to filter his blood and produce urine. When stones develop in your dog's kidneys or urinary tract, he has a condition known as nephrolithiasis. There are different types of kidney stones; treatment depends on what kind of stone your dog has. Fortunately, kidney stones are rare in dogs.
A Stone is Not a Stone is Not a Stone
Your dog may have strained to urinate -- just for a little smidge of pee -- and when he finally did pee, he may have startled you with bloody or amber-colored urine. All are signals it's time to see a vet to determine what's wrong with your dog. In addition to a thorough exam, the vet will perform a urinalysis and an ultrasound to confirm that our pup does have kidney stones and identify what kind of stones he has. According to Whole Dog Journal, struvite and calcium oxalate stones are the most common types of stones in dogs; other types are urate, silica, xanthine, cystine, calcium phosphate and mixed stones.
Ideally, your dog's kidney stones can be treated with diet alone. It takes time to go this route, potentially as long as five months. Struvite stones tend to be receptive to dietary treatment because of their shape and composition. The ideal diet for a dog with struvite kidney stones is one with lower magnesium and phosphorus -- the foundation of struvite -- as well as a lower level of protein and a bit more salt. The lower protein reduces the amount of ammonia in a dog's urine while the added salt encourages your dog to drink water. As the dog drinks more, his urine dilutes more, eventually dissolving the stones. Commercial foods are available from your vet that meet the criteria for dissolving struvite stones. The special diet is very low in protein, so it should only be fed long enough to dissolve the stones. Urate, cystine, xanthine and compound stones also respond to dietary changes for treatment, though they also may require medicine to help in their dissolution.
Urate stones are treated with diet and medication. A low protein diet, also restricted in purines, which are part of uric acid, will help dissolve the stones. The medication allopurinol is also used to reduce the level of uric acid in your dog's body. Medication is necessary to dissolve cystine stones, which won't respond to dietary changes alone. Cuprimine is a more affordable medication, though it can have serious side effects; Thiola has fewer side effects, but often is prohibitively expensive.
Minimally Invasive Procedures
Extracorporeal shock-wave lithotripsy is a minimally invasive way to address kidney stones. External shock waves pass through a water medium to shock the stone up to 2,500 times, reducing it to powder to pass through the ureter into the bladder. This is effective for stones smaller than 3/4 of an inch in diameter. Larger stones are candidates for percutaneous nephrolithotomy, a minimally invasive surgical procedure that extracts the stone through a small incision. A tube is inserted into the kidney, the stone is broken up and then extracted through the tube. Stones that don't respond to medicine and dietary changes, such as silica, calcium phosphate and xanthine, respond well to lithotripsy.
Surgery and Calcium Oxalate Stones
Calcium oxalate stones require surgery to remove because they don't respond to diet or medicine. Dr. Ron Hines of 2ndChance.info notes removing calcium oxalate stones from the kidneys is extremely difficult and perhaps unwise. There are few board-certified veterinary surgeons in the U.S. able to perform the delicate surgery. Factors determining whether surgery is advised include where the stones are located in the kidneys, their size, shape and number, as well as how often the dog is experiencing urinary tract infections. He notes stents can be inserted if a stone is positioned to block a ureter. Fortunately, 90 percent of calcium oxalate stones occur in the bladder, where it's much easier to remove them.
Living With Stones
The diet used to dissolve kidney stones won't be the diet your dog relies on after his stones are gone. However, he likely won't enjoy his pre-stone diet either. The vet will determine what type of diet is best for your dog to ensure he doesn't have a repeat occurrence of kidney stones. Ensuring your dog drinks plenty of water is important as well, as water helps keep his urine diluted to keep crystals from forming.
- PetMD: Kidney Stones in Dogs
- 2ndChance.info: Bladder and Kidney Stones in Dogs and Cats
- VCA Animal Hospital: Struvite Bladder Stones in Dogs
- WebMD: Bladder and Urethral Stones in Dogs
- Whole Dog Journal: Treatment and Prevention of Kidney and Bladder Stones
- 2ndChance.info: All About Oxalate Bladder And Kidney Stones In Your Dog And How To Manage Them
- 2ndChance.info: Stone Disease and Urinary Obstruction in Dogs and Cats Are Minimally Invasive Alternatives an Option for your Patient? -- Allyson C. Berent, The Animal Medical Center