The Rip Van Wrinkler, XXIII, Issue 1, February 2019

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2. Unraveling the Phenotypic and Genetic Complexity of Canine Cystinuria (Paula Henthorn)

3. Nutritional Recommendations for Urinary Stones (Tufts)


Dr. Jean Dodds' Pet Health Research Blog

By W. Jean Dodds, DVM on January 6, 2019

In July 2018, the United States Food and Drug Administration (FDA) issued a public notification about an uptick of reports of canine dilated cardiomyopathy (DCM) – a type of heart disease that can lead to congestive heart failure – in dogs eating certain pet foods containing peas, lentils, legume seeds or potatoes.

In case you are unfamiliar with DCM, the condition can be hereditary and/or dietary, and also can be idiopathic (cause unknown). In general, DCM occurs when an insufficient amount of the amino acids cysteine and methionine are ingested, which dogs use to synthesize taurine in the liver. Taurine is important as it prevents or slows the progression of DCM.

Due to the FDA’s announcement, some researchers quickly pointed to grain-free formulations as the culprit.

Dr. Dodds and Hemopet have urged caution about jumping to any conclusions in earlier postings. We referenced previous studies that demonstrated lower taurine concentrations in the blood from dogs eating formulations that contained combinations of grains and proteins such as barley and turkey or lamb and rice, and one that showed beet pulp as possibly instigating lower taurine concentrations.

Since July, two notable studies have been published.


PAULA HENTHORN at Tufts' Canine and Feline Breeding and Genetics Conference, 2013

Unraveling the Phenotypic and Genetic Complexity of Canine Cystinuria

Cystinuria is a disease of disrupted amino acid transport in the collecting ducts of the kidney failing to reclaim certain amino acids (cystine and the dibasic amino acids ornithine, lysine and arginine referred to as COLA). The increased urinary COLA concentrations reach saturation levels for cystine, which precipitates to form crystals and stones resulting in renal to urethral obstructions. Mutations in the SLC3A1 and SLC7A9 genes give rise to cystinuria in the vast majority of cystinuric humans, where the disease shows autosomal recessive or dominant inheritance (reviewed in Palacin et al. 2001; Chillaron et al. 2010).


Nutritional Recommendations for Urinary Stones

Clinical Nutrition Service
Foster Hospital for Small Animals 200 Westboro Road
North Grafton, MA 01536
Phone: (508) 887-4696 Attn: Nutrition Liaison
Fax: 508-887-4363
Nutritional Recommendations for Urinary Stones

Stone type: Cystine

Nutritional Goals
• Complete and balanced diet
• Increase moisture to dilute urine
• Reduce building blocks of stones
• Increase compounds that prevent stones

If your dog has been diagnosed with cystine urinary stones, diet is often an important factor in managing urinary stones as some stones can be dissolved with special diets or special diets can be used to reduce the risk of more stones developing in the future.

Stone Prevention:
• One of the most important factors in preventing all types of urinary stones is having dilute urine. Most dogs do not drink enough water to keep their urine dilute enough to reduce their risk of stone formation. Canned diets are generally preferred for dogs with a history of stones because they are naturally much higher in water than dry diets (although most will still need water added to achieve our urine dilution goals). We recommend adding water to both dry and canned foods to achieve the urine dilution goal. This measurement is called urine specific gravity (USG). The goal for animals with a history of urinary stones is a USG less than 1.020 (for reference, water is 1.000). This can be measured by your veterinarian, or you can collect a urine sample and test it yourself with a device called a refractometer, which can be purchased online at sites such as

• There are many diets currently available that are designed to help reduce the occurrence of various types of crystals and stones. These diets are only available from veterinarians or with the prescription from a veterinarian. These diets have been carefully formulated and extensively tested to produce urine that should reduce the risk of stone recurrence. However, these diets do not prevent stone formation in every dog. Because these diets are so carefully designed, any additional foods added to them could make them less effective, so treats, table foods, supplements, rawhides, dental chews, or any other foods need to be carefully considered.

• While diets you can buy from the pet supply store and home-made diets are often desired by dog owners, these diets may not have any benefits for stone prevention and in some cases may encourage stone formation. As such, we strongly recommend the therapeutic diets designed for stone prevention unless other health concerns prevent their use.

• Cystine:

Cystine stones are caused by a genetic abnormality in the kidney. When it occurs in unneutered male dogs, it may resolve after neutering. Female dogs or neutered male dogs that develop cystine stones may benefit from special diets to reduce the risk of recurrence. These diets typically are made from mainly plant proteins, rather than meat, to reduce the amount of cystine in the diet. These diets have some risks associated with them, so additional supplements are generally recommended and animals on these diets should have regular veterinary checkups.

Cystine stones are most soluble when the urine is more alkaline.

Diet Recommendations:
• Below are some commercial foods that meet our nutritional goals. These veterinary therapeutic diets are available only from a veterinarian or online with a written prescription). You can mix and match the canned and dry of the same brand based on your dog's preference, but canned is likely more effective.
• These recommended diets are all veterinary diets of the highest quality ingredients, nutritional expertise, and research. Other diets, even if they have a urinary claim, may not be appropriate for your cat and may not have the research and quality control necessary to help reduce the risk for your dog’s urinary stones.
• Please see our website for more discussion of what makes these special diets different from diets that you can buy without a veterinarian’s approval:
• For cystine stones, our first choice for dietary management is the Royal Canin Urinary UC Low Purine Diet, which is specifically formulated to help with these stones and appropriate to feed long term. Additional diets that are lower in cystine are included as well.

Royal Canin Veterinary Diet Urinary UC Low Purine*
Royal Canin Veterinary Diet Urinary + Hydrolyzed Protein dry
Royal Canin Veterinary Diet Vegetarian dry
Royal Canin Veterinary Diet Vegetarian canned
• Add water to both canned and dry food, starting with just a few drops and keep increasing until urine specific gravity meets our goals.

Supplement Recommendations:
• Unfortunately, there is little regulation of supplements for people or animals (neither safety nor effectiveness has to be proven prior to marketing) and some of these products may be harmful rather than helpful. Therefore, we are quite selective when it comes to recommending specific supplements. We usually only recommend a product where there is adequate data to show that it is safe and has a reasonable expectation of effectiveness.
• Some dogs with cystinuria also lose a compound called carnitine in their urine and others may not be able to make enough taurine. Both of these compounds are important for overall health.

• All of the diets designed to prevent stone formation are tested as the only source of food, which means that adding in treats could reduce their effectiveness. If treats are important to you and your dog, using the dry version of the canned stone diet may be an option. You can also bake thin slices of the recommended canned version in the oven until they’re dried out. Alternatively, you could use certain fruits and vegetables that are low in stone building blocks. Some treats are listed below that are generally safe in small quantities for most dogs with stones (although they still may interfere with the diet function).
• All dogs should receive a maximum of 10% of the daily calorie intake (40 kcal/day) from treats. If the total amount of the diet being fed is altered, the treat allowance should be adjusted accordingly so that treats
never exceed 10% of total calories to avoid unbalancing the commercial diet by nutrient dilution and severely decreasing the effectiveness against stones.

• Some treat suggestions include:
Butternut or acorn winter squash (cooked)
Sweet red peppers
Green peas

Foods to AVOID:
• Avoid macadamia nuts, garlic, onions, grapes, raisins, and other foods known or suspected to be toxic to dogs.
• Avoid all types of added meats, bully sticks, pig ears, antlers, rawhides, or other high protein, meat-based treats as they can interfere with the beneficial properties of the diet and increase stone risk.
• Commercial canned broths should also be avoided as even the low sodium options are often too high in salt and most of these products contain unknown amounts of onion and garlic. If you would like to put a small amount of broth on their food, it is best to boil meat or fish in plain water with no seasoning and use this broth without the meat.

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