Dissolving and Preventing Urate Bladder Stones

Ammonium urate stones are the most common type of urolith/bladder stone in dogs. Risk factors for their formation include internal and external factors.   Foods-those high in purines contribute to the formation of these stones because purines are a precursor to uric acid. Any type of meat is higher in purines than vegetarian sources, with organ meats and yeast having the highest amount of purines. Dry kibble is more likely to contribute to stone formation than canned food. Higher amount of protein also increase the formation of stones (this is the reason that we add distilled water to the RC Hepatic). Puppy foods are higher in protein than adult foods, and the incidence of urate bladder stones in dogs with liver shunts is common in dogs less than one year of age. Urate urinary crystals are a serious symptom and a sign of  minimal, or subclinical hepatic encephalopathy.

Risk factors increase in male dogs of certain breeds, eg. dalmatians, English bulldogs, miniature schnauzers, yorkshire terriers and shih tzus. Liver disease, especially when bile acid results are elevated, increases the likelihood that a dog will form urate stones. For example, dogs with portosystemic shunts or hepatic microvascular dysplasia are at increased risk for forming urate bladder stones. When fed a meat-based protein, levels of uric acid increase and subsequently ammonia also increases and urinary pH becomes more acidic.

I’ve had many dogs with severe liver problems whose bladder stones have been dissolved. Augie is a three year old, five and a half  pound yorkie with a presumed liver shunt that was surrendered to RetroDoggyRescue in Feb/11. Previously, he had multiple seizures and bladder stone surgery when he was 13 months old. His owners did not provide any type of prescription food or liver support supplements, and at the time of his surrender (5 months after his initial surgery), he already had a conglomeration of bladder stones that measured about 2.5 mm to 5 mm.   His post bile acids were around 240 and he was placed on prescription food for the liver made by Royal Canin (low protein/vegetarian) with water added, multiple small meals and given PediaSure Vanille with fiber mixed with water to increase hydration.

Within about 6 weeks, his bladder stone had dissolved completely. Liver support supplements and probiotics were an important component to his bladder stone dissolution. Azodyl, a probiotic for kidney failure, also decreases ammonia and normalizes the urea cycle. Another probiotic that decreases ammonia is VSL3. Zinc is also important in stone dissolution. One vet has also recommended the use of Actigall (Ursodiol), a prescription liver antioxidant usually used in dogs with gall bladder problems.

The low purine food that Augie was on, combined with supplements,  prevented the formation of further urate stones by controlling the amount of urice acid in his system;however, when his food was changed in July/11 because he was having hypoglycemic seizures, he developed another stone within 3 weeks! Despite the small size of the stone, it kept getting lodged in his urethra so RDR and his vet decided to have it surgically removed and have him neutered. Augie also had a liver and intestinal biopsy done; results were consistent with a liver shunt and protein-losing enteropathy. He was one sick puppy for over a week and I had to syringe PediaSure for all of his meals for a week. That was at the end of August/11 and as of today he’s stone free (over a year).

Another foster dog, a 5 month old maltese puppy, already had a 3mm bladder stone. Within 3 weeks, when he had his liver shunt surgery, this stone had dissolved (verified with ultrasound). He had been on similar prescription food and supplements. Several dogs have had heavy concentrations of urate crystals in their urine that have been dissolved before their liver shunt surgery.

I’ve been taking care of dogs with liver disease for six years and had success managing symptoms of liver disease and dissolving bladder stones. I’m not a veterinarian or nutritionist but have lots of hands-on experience and am passionate about researching liver disease. The prescription food and medications have to be obtained from your veterinarian, and any suggestions checked with them.

The article below reminded me of Julie, the dalmatian with a liver shunt that had urate crystals present, but never formed stones.  Any dalmatians that are forming urate stones or have urinary urate crystals would benefit from having  a bile acid test done to check liver function.

http://www.veterinarypartner.com/Content.plx?P=A&A=1683&S=0&EVetID=0   Prevention and Monitoring   As for periodic monitoring to be sure no new stones are likely to form, several protocols have been advocated.   Urinalysis and either ultrasound or double contrast cystogram (radiography with dye) should be performed every 1 to 2 months. If after 6 months, no stones have recurred then testing can be extended to every 4 months. If stones are small, they can be flushed from the bladder without surgery. This is a complete method but all that ultrasound/contrast radiography is going to get expensive quickly.     The 24-hour uric acid production test involves collecting all the urine a dog produces over either a 12-hour period and multiplying the value by two, or collecting 24 hours of urine. This typically involves some kind of urine collection bag and a urinary catheter sewn in place (or a very, very cooperative dog). It is difficult to keep a urinary collection system in place in a normal dog and thus this test is problematic to run. The urine is collected, sent to the lab, and the total production of uric acid is determined. This will tell if the dog is on track to avoid future stones or not. Because the collection is so difficult, many skip it and simply do the above monitoring. The goal value is less than 300 mg/kg of body weight daily.     The uric acid (or urate) to creatinine ratio test. The idea here was to use a single urine sample to get an idea of how much uric acid the dog was producing. This ratio seemed like a good idea at the time and was certainly easier than the 24 hour urine collection but it has not panned out as a valid test to predict stone re-formation but will tell the veterinarian if the pet owner is cheating on the diet.     The blood urea nitrogen level (BUN) is a common parameter assessing kidney function. In most cases, we are concerned about its being elevated but in monitoring stone forming Dalmatians a lower than normal BUN (ideally  less than 10mg/dl) indicates that no dietary cheating is going on. Your veterinarian is likely to pick and choose from these tests to put together a protocol they are comfortable with that fits your budget.     Off Limits for Stone-Forming Dalmatians   Cyclosporine (Atopica®) for the treatment of airborne allergies. Unfortunately, this medication, which is successful in managing itchy skin due to airborne allergies, increases uric acid levels in urine. An itchy stone-forming Dalmatian must stick to other methods of itch control.     Brewer’s yeast supplements have been popular (though ineffective) for flea control and generally represent a tasty B vitamin supplement for dogs. This supplement is high in purines and not appropriate for stone-forming Dalmatians.   Vitamin C is a common supplement for dogs, especially in joint health nutritional products. Vitamin C is likely to overly acidify the urine of a stone-forming Dalmatian and should not be used.   Certain cancer chemotherapy protocols involve interactions with allopurinol and must be modified. No one has formally tested the vegetarian diets for dogs to determine if they are adequately low in purines for stone prevention. Their use is a last resort for stone prevention (i.e. if the dog simply will not eat any of the appropriate foods.)