Some dogs with struvite crystals (bladder stones) are medically managed by a feeding program that is designed to dissolve crystals by acidifying the urine. Although other treatment methods like surgery or lithotripsy can be used, calculolytic diets are chosen for reasons like financial constraint of the owner and aging or poor health of the dog. The diets are available commercially and require about 14 weeks to be effective. Calculolytic diets are often used in conjunction with other treatments to make sure that any missed fragments or small stones are dissolved.
Characteristics of the Diet
Medically managed diets for bladder stones work by making the urine more diluted and acidic and decreasing the minerals that contribute to stone formation, such as magnesium, phosphorus and ammonium. The diet is low protein and high sodium. The sodium encourages the dog to drink more water, which helps the dissolution process. The diet doesn't meet all canine nutritional needs; it is a temporary treatment that is combined with antimicrobials to reduce infection risk. Diagnostic imaging and urinalyses are used to make sure the diet is effective.
Not all dogs are appropriate patients for the high salt, high fat diet. Puppies, or dogs with a history of pancreatitis, kidney disease, heart disease or high blood pressure would not be able to tolerate this treatment method. In addition, the dissolving stones sometimes move down through the narrow urethra and get stuck, which can be life threatening. Veterinarians work with owners to make the best decision about what kind of therapy to use.
Antibacterial therapy is usually a part of the overall treatment for struvite crystals. Urinary tract infections cause urine to become more alkaline, which increases the pH above 7.0 and, according to Race Foster DVM, cofounder of Peteducation.com, contributes to struvite crystal formation. Because it is important to prevent any further infections, antibacterials are an important part of medical management.
Struvite crystals can form in any part of the urinary tract. One treatment consideration is the size and location of the stone. Dr. Foster states that preventing stones from recurring includes: adequate hydration, use of special diets and controlling the pH of the urine. Because crystals are often formed secondary to urinary tract infections, ongoing assessment is needed.
There are known contributors to struvite crystals, and managing them benefits your pet's health. Urinary tract infections, dehydration and high protein diets all contribute to increased risk. Dr. Carl Osborne, DVM and professor at the College of Veterinary Medicine, University of Minnesota, advises that the best way to prevent struvite conditions is to monitor pets for urinary tract infections. Plenty of fresh water, exercise and proper diets can help keep dogs healthy.
- National Institutes of Health: The Canadian Veterinary Journal: Dissolution of infection-induced struvite bladder stones by using a noncalculolytic diet and antibiotic therapy
- Pet Education: Bladder Stones (Urinary Calculi in Dogs)
- dvm360: Stalking stones: An overview of canine and feline urolithiasis
- dvm360: Improving management of urolithiasis: canine struvite uroliths