A healthy diet is a powerful weapon in promoting good health and also can be used to help manage health-related issues. In part 1, we looked at how obesity and diabetes can be directly affected by a pet’s diet. Now we’ll take a closer look at how food can impact urine crystals, a condition known as crystalluria, and urinary stones, a condition known as urolithiasis.
The problem with urinary crystals and stones
Although dog and cat urine is about 95 percent water, it’s still a complex solution that contains substances that can either cause or prevent formation of mineral crystals and urinary stones (aka uroliths). Urinary crystals are microscopic structures, while uroliths are larger rock-like clumps of minerals that are often visible without a microscope. Urinary stone formation can occur anywhere along the urinary tract, and depending on where the stone is located, it may be called a kidney stone or a bladder stone. Bladder stones are more common than kidney stones; however, either can result in serious illness when they cause irritation, pain or even block the urinary tract so your pet can’t urinate. Crystals found in urine don’t automatically lead to urinary stone formation, but they do represent a risk factor for stone formation.
Urinary crystals and stones are made of several different minerals and compounds, such as magnesium, ammonium, phosphate, calcium and oxalate. The most common types of crystals and stones in cats and dogs are struvite (aka magnesium, ammonium and phosphate) and calcium oxalate. If your pet develops kidney or bladder stones, your veterinarian will recommend sending a sample to a specific laboratory so that the mineral content can be identified. By knowing what minerals are in a urinary stone, your veterinarian will recommend a treatment plan, usually including an appropriate food to help treat your four-legged friend and possibly help prevent stones from occurring again.
Struvite crystals and stones
In cats, we don’t fully understand what leads to struvite crystal and stone formation. But we do know that urine pH, mineral concentrations in food and water consumption are all factors that play a role. Because struvite crystals form in alkaline urine, many cat foods contain ingredients to help make the urine more acidic. Lower levels of magnesium and phosphorus in a cat’s diet will lead to lower concentrations of these minerals in urine, helping to lower the risk of struvite crystals. Finally, since dilute urine contains lower concentrations of crystal or stone components, increased water consumption is recommended for cats with urinary problems, often by adding canned or wet foods to the diet.
Unlike cats, struvite crystals and stones in dogs are primarily associated with bacterial urinary tract infections. Treatment of the infection is essential to resolve the problem.
Struvite stones can be eliminated through urohydropropulsion (a procedure using sterile saline to force stones out of the bladder), cystoscopy (insertion of a very small tube with a camera allowing visualization and removal of stones), surgery or feeding therapeutic diets which are formulated to dissolve stones. In dogs, lithotripsy (use of shock waves or laser to break up the stone) is another option. Veterinarians frequently recommend long-term feeding of a therapeutic diet to prevent recurrence of urinary crystals or stones.
Calcium oxalate crystals and stones
As with struvite, there are still many uncertainties regarding the exact cause of calcium oxalate stones. Research indicates that decreased urine pH and urine containing high levels of calcium or oxalates predisposes a pet to developing this type of crystals. Diets causing high urine acidity may be involved. The incidence of pets with calcium oxalate stones has increased over the last 30 years and may be related to the increased use of foods that acidify urine.
Unlike struvite stones, calcium oxalate stones can’t be dissolved by changing the pet’s diet. These stones must be removed by urohydropropulsion, cystoscopy, surgery or lithotripsy. Food can be used in an effort to prevent additional stones from forming. Veterinarians will often recommend a prescription diet that promotes dilute urine with a neutral pH, optimal amounts of calcium and magnesium, and controlled levels of sodium. Feeding a canned food or adding water to a high-quality, highly digestible dry food is a good way to get cats and dogs to produce more dilute urine.
Many other health issues can be addressed through diet, although not necessarily treated by food alone. When dogs and cats develop health-related conditions that keep them from eating diets designed for healthy pets, that’s when they can benefit most from specially designed foods. If you have any questions about your pet’s diet, be sure to discuss your concerns with your veterinarian.