I get emails very often regarding pets with stones in the bladder or kidneys. Stones are painful, causing straining, bloody urine, incontinence, urine dribbling, frequent urination, malodorous urine, and occasionally obstruction which can lead to death. No pet should suffer from this malady. Stones are treatable and preventable, except in very rare instances.
The two most common types of stones found in cats and dogs are struvite (the large white stone in the photo taken from a Shih Tzu) and oxalate (the small, sharp, tan stones in the photo taken from a Golden Retriever). Struvite stones occur in urine with a high pH (greater than 7.5 generally), normally in response to bacterial infection in the bladder. These stones are easy to prevent by keeping pets free from urinary tract infections and treating infections appropriately. Infections should be treated with effective antibiotics, preferably chosen after performing a urine culture and sensitivity. The urine should be tested again after treatment to be certain the infection is completely cured.
Oxalate stones are found in urine with a low pH (less than 6.0 generally) and are more common in certain breeds that may have a genetic predisposition, including Maltese, ShihTzu, Yorkie, Miniature Schnauzer, Bichon Frise, and Lhasa Apso. Oxalate stones are also found secondary to diseases like Cushing's disease, hyperparathyroidism, and any disease that results in high calcium levels. Over-supplementation with calcium or Vitamin C, drugs like furosemide and steroids, and certain foods like soy and wheat can promote formation of oxalate stones.
Once stones are diagnosed, pets must be treated appropriately to keep stones from returning. Moisture is one of the main factors to be addressed. A high moisture, meat-based diet will make the urine more dilute and help flush crystals out of the kidneys and bladder. Meats are naturally low in oxalates and make the best diet for pets prone to oxalate stones. Dry kibble is a low-moisture diet and is absolutely not appropriate for pets with urinary stones. Prescription urinary and stone diets have not been proven to prevent stone formation; they work because chemicals and salt are added to the food to increase water consumption and change the urine pH. Personally, I have had great success keeping pets stone-free by prescribing a species-appropriate raw, freeze dried, or home cooked meal.
Urine testing should be performed frequently (monthly after initial diagnosis and treatment, decreasing to every 3 months after 3 negative urine sample) to make sure no signs of infection or crystals are returning. The urine specific gravity (measure of how dilute the urine is) should be maintained below 1.030 for cats and 1.025 for dogs. If animals consistently have a urine pH above 7.5, adding cranberry to the diet can be beneficial. Glucosamine/chondroitin products can decrease bladder inflammation. Supplements to boost the immune system to fight infection should also be added to the regimen. These pets should be given a daily probiotic, as they will suffer from overgrowth of harmful bowel bacteria secondary to antibiotics and infection.
Keep your pets free from stones by feeding a healthy, species-appropriate diet. If you would prefer to prepare home-cooked meals, consult with a veterinary nutritionist so you can provide a balanced, healthy program for your pet. Educate yourself about kidney and bladder disease so your pets can remain healthy.