Urate, Cystine, and Other Less Common Urinary Stones
Treatment and prevention of urate, cystine, xanthine, calcium phosphate, silica and compound uroliths.
Article by CJ Puotinen and Mary Straus, published in the Whole Dog Journal, June 2010
Also see these related articles:
Pictured is Gigi, one of the first two Dalmatians with a normal uric acid gene registered in Britain. See British Kennel Club Registers First LUA Dalmatian below for more information.
Canine kidney and bladder stones may be painful and life-threatening, but an informed caregiver can help prevent them. By far the most common uroliths or stones in dogs are struvites (see Struvite Crystals and Stones) and calcium oxalate stones (see Calcium Oxalate Kidney and Bladder Stones). These two types represent about 80 percent of all canine uroliths.
Now we address the remaining stones that can affect our best friends: urate, cystine, calcium phosphate, silica, xanthine, and mixed or compound uroliths.
Of the remaining stone categories, urate or purine stones are the most common. They contain ammonium acid urate, sodium urate, or uric acid.
Only 6 to 8 percent of all uroliths are urate or purine stones, but their presence in certain breeds is significant. Dalmatians, English Bulldogs, Russian Black Terriers, Large Munsterlanders, Weimaraners, German Shepherd Dogs, Giant Schnauzers, American Staffordshire Terriers, Australian Shepherds, and South African Boerboels develop urates because of a genetic metabolic abnormality. Miniature Schnauzers and Yorkshire Terriers do so as a result of their tendency to have portosystemic shunts, which are abnormal blood vessels that bypass the liver, predisposing dogs to urate stones. These stones can form in dogs of any age, from very young puppies to seniors, but the most common age for forming urates is 1 to 4 years.
Of the breeds that develop urate stones, Dalmatians are most adversely affected. Between 1981 and 2000, the University of Minnesota College of Veterinary Medicine's Minnesota Urolith Center analyzed 7,560 stones from Dalmatians. Of these, 97 percent were from males and 95 percent were composed of urates. It's estimated that between 27 and 34 percent of male Dalmatians form urate stones, while the incidence in females is much lower.
It's tempting to assume that any stone a Dalmatian forms is a urate, but although 97 percent of stones from male Dalmatians were urate, they also included small percentages of struvite, xanthine, calcium oxalate, cystine, calcium phosphate, silica, and mixed or compound stones. The uroliths formed by female Dalmatians were 69 percent urate and 29 percent mixed or compound, with 2 percent struvite and 0.7 percent xanthine. Correct identification is a crucial first step in treating and preventing uroliths in all breeds, including Dalmatians.
The culprits in urate stone formation are purines, a type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. As dietary purines degrade, they form uric acid, which is best known in human medicine for its connection to gout, a sharply painful form of arthritis. In susceptible dogs, purines trigger the formation of urate uroliths.
Urate stones are radiolucent -- that is, they cannot be identified in abdominal X-rays -- so their diagnosis is often made by the use of ultrasound, contrast dye X-rays, or analysis of urinary crystals or stones that were collected or removed.
The key to keeping urate-forming dogs healthy is to feed them a low-purine diet. Without the purines that trigger urate stone formation, even susceptible dogs can lead normal lives.
Some Dalmatian owners believe that giving their dogs who are prone to forming urate stone only mineral-free distilled water has helped prevent more stones from forming. No scientific evidence for this exists, however, and the quantity of water the dog consumes may be more important than its mineral content.
Because urate stones develop in acidic urine, an added prevention strategy is to feed foods that have an alkalizing effect. In general, meat is an acidifying food while most fruits and vegetables have an alkalizing effect. Vegetarian dog foods are sometimes recommended for this reason, but we consider vegetarian foods incomplete. Also, foods that use soy as a protein source are inappropriate for urate-forming dogs because soy is high in purines. However, soy-free vegetarian foods could be used as a base to which eggs, yogurt, cheese, and other low-purine protein sources are added. The same is true of some dog food pre-mixes, such as Sojo’s Grain Free Dog Food Mix. Sojo’s Complete is based on sweet potatoes, turkey, and eggs and might also be appropriate for dogs who are prone to forming stones. Avoid mixes that contain a lot of alfalfa, oats, or other foods that are high in purines (see Purine Content of Various Foods below).
Urate stones can be dissolved with a combination of a low-purine diet, urine alkalization, and control of secondary infections. The target range of urine pH during dissolution is 7.0 to 7.5. Care must be taken not to alkalize too much, making the urine pH higher than 7.5, because that can lead to the formation of calcium phosphate stones or shells around urate stones, making them difficult or impossible to dissolve.
The xanthine oxidase inhibitor allopurinol (brand name Zyloprim) may be prescribed short-term to reduce or inhibit the dog’s production of uric acid, which can help dissolve stones. This drug should not be used in patients with portosystemic shunts. A low-purine diet must be fed while giving allopurinol, as otherwise it predisposes dogs to the formation of xanthine stones and shells, making dissolution difficult. The long-term use of allopurinol as a preventative is not recommended but can be considered at low dosages when problems persist despite other treatment.
On average, it takes about 3½ months for stones to dissolve using allopurinol in combination with a low-purine diet and urinary alkalinization, but it can take as little as one month or as long as 18 months. As stones become smaller, they may move into the urethra and cause obstruction.
Some cases of severe kidney stones presumed to be ammonium urate resolved spontaneously following surgical shunt correction alone.
Urinary pH can be monitored using test strips with the goal of maintaining a neutral (7.0) pH in dogs prone to urate stones. Test strips can be held in the urine stream or urine can be collected in a paper cup, bowl, or other container for testing. Collecting the urine makes it possible to check for tiny stones or gritty “gravel” that the dog might be passing as well as any blood, pus, or other indications of infection. The recommended testing time is first thing in the morning, before feeding.
A change in urinary pH does not indicate the presence or absence of stones but does reveal conditions that are more or less likely to trigger stone production and will show the effect of dietary changes on the dog’s pH. A sudden jump in pH may signal a bacterial infection, which requires medical attention. It’s important to control urinary tract infections in dogs prone to forming stones.
If urine remains acidic and crystalluria (crystals in the urine) persists, alkalizing agents such as potassium citrate or sodium bicarbonate can be added.
Hyperuricosuria is characterized by the excretion of uric acid leading to urate stone formation. After the defective gene that causes hyperuricosuria was discovered by researchers at the University of California, Davis, a test was developed to detect the mutation associated with the disease. This test is valid for all breeds.
Dogs affected by hyperuricosuria have two copies of the mutation, one inherited from each parent. Dogs with only one copy of the mutation are symptom-free carriers who pass the mutation on to an average of 50 percent of their offspring. Breeders can use DNA testing to identify carriers and effectively eradicate hyperuricosuria from their lines in breeds other than Dalmatians. (At present, all Dalmatians registered by the American Kennel Club in the United States are affected by the mutation. See LUA Dalmatians below.) When both dam and sire are clear of the mutation, all of their puppies will be clear as well.
The DNA test identifies dogs in three categories: clear of hyperuricosuria (the dog has two copies of the normal gene and no mutation), a carrier of hyperuricosuria (the dog has one copy of the normal gene and one of the mutation), or affected with hyperuricosuria (the dog has two copies of the mutation, causing high uric acid levels that can lead to urate stone disorders).
All dogs affected with hyperuricosuria are potential urate stone-formers. At any time, a combination of high-purine foods, insufficient fluids, insufficient opportunities to urinate, and overly acidic urine might cause the formation of urate uroliths. Periodic routine urinalysis to check for urate crystals can be used to monitor dogs with hyperuricosuria. The most accurate sample for this purpose is collected in the morning, assuming the dog has not urinated all night, so the urine is more concentrated. The sample should be collected in a clean glass, plastic, or other chemically inert container. To avoid false crystallization, the sample should not be refrigerated and should be tested within 30 minutes or as soon as possible.
While many Dalmatians never generate stones, it isn’t safe to assume that they can’t. In one widely reported case, a 13-year-old Dalmatian who had never shown symptoms began receiving two spoonfuls of a new supplement per day. Prior to this, his diet had been the same for all of his adult life. Within a few weeks, his urinary tract became completely obstructed by urate stones. While the supplement was low in protein (only 14 percent), its protein source was liver, a high-purine food.
Reducing purines in food is an effective way to reduce the risk of urate stones. Because most high-protein foods are also high in purines, veterinarians often recommend switching urate-forming dogs to a low-protein diet. However, it is not the quantity of protein that causes urate problems, it’s the type of protein. Dalmatians and other urate-prone dogs thrive on protein-rich diets that are low in purines, while these same dogs can develop stones after eating low-protein foods that contain even small amounts of high-purine ingredients. Low-protein diets can lead to nutritional deficiencies when fed to adult dogs for long periods, and they are not appropriate for puppies and pregnant or nursing females at all. (See The Side Effects of Low-Protein Diets below.)
Because it’s difficult to find commercial pet foods that are low in purines without being nutritionally deficient, many owners of urate-forming dogs feed a home-prepared diet (see Homemade Diets for general information that can be modified using the information below).
Australian veterinarian Ian Billinghurst, whose book Give Your Dog a Bone introduced the BARF (Bones and Raw Food or Biologically Appropriate Raw Food) diet to dog lovers around the world, describes how to adapt his menus for urate-forming dogs in his report, Preventing Urate Stone Formation In Dalmatians Using A Basically BARF Diet:
“In Western countries today,” he says, “I am led to believe that a typical homemade diet for stone formers would contain about 80 percent rice, 10 percent vegetables, and 5 percent meat. This is an appalling diet to feed any dog. This is borne out by dogs forced to endure it. They suffer from numerous problems including continual hunger, a lack of energy, poor coat condition, and difficulty in maintaining weight or severe losses of weight.” Such a diet is not only deficient in protein, fat, vitamins, and minerals, he says, but it does not prevent stone formation.
The raw meaty bones Dr. Billinghurst recommends are chicken necks, chicken backs, chicken wings, and turkey necks. “Use plenty of puréed or pulped vegetables,” he says, “including lots of leafy greens. The diet could also include eggs, cottage or ricotta cheese, yogurt, and olive or flaxseed oil, supplemented with vitamin B complex, vitamin E, kelp, and a teaspoon of cod liver oil several times a week.” Cod liver oil is important for urate-forming dogs fed a homemade diet that does not include liver.
Feeding a changing variety of eggs, cheese, dairy products, and small amounts of medium-purine meat, poultry, and fish along with low-purine vegetables, fruits, and supplements – as well as ample water to keep urine diluted – can help any urate-forming dog stay healthy and happy. See Commercial Dog Food Makes Me BARF! for an example of a raw diet that worked for a confirmed stone-forming dog.
Cystine is a sulfur-containing amino acid essential to the health of skin, hair, bones, and connective tissue. Excess cystine is normally filtered by the kidneys so that it doesn’t enter the urine, but some dogs and humans are born with cystinuria, an inherited metabolic disorder that prevents this filtering action. When cystine passes into the urine, it can form crystals and uroliths.
Cystine stones are rare, representing 1 percent or less of uroliths identified in laboratories. Although any breed can develop cystinuria, certain breeds are most affected. An estimated 10 percent of male Mastiffs (pictured at right) have cystinuria. It is also common in Newfoundlands, English Bulldogs, Scottish Deerhounds, Dachshunds, Staffordshire Bull Terriers, and Chihuahuas. Cystine stones are faintly radiopaque, which makes them more difficult to see on X-rays than stones that contain calcium.
There are at least two types of cystinuria. The more severe form affects Newfoundlands and, rarely, Labrador Retrievers, and possibly some other breeds and mixes. In these dogs, males and females are equally affected (though as always, males are more likely to become obstructed). The age at onset can be as young as 6 months to 1 year. Recurrence of stones following surgery is more rapid in these dogs, and they are more likely to form kidney stones. The gene that causes cystinuria in these breeds has been identified and a simple, reliable genetic test can identify both affected dogs and carriers.
In other breeds, dogs with cystinuria are almost always male. No genetic test is available for them, though the University of Pennsylvania School of Veterinary Medicine (PennVet) is collecting blood samples from affected Mastiffs and their genetic relatives to try to produce a DNA test. The average age at onset of clinical signs is about 5 years.
A basic urinalysis can sometimes detect cystine in urine, though this is the least reliable method of detection. A nitroprusside (NP) test performed at the University of Pennsylvania (PennGen) is considered more reliable. A quantitative amino acid analysis performed by PennGen or a human medical laboratory is most reliable but very expensive. If cystine is found in the urine on any of these tests, the diagnosis is considered positive for cystinuria, though that doesn’t necessarily mean the dog will form stones. Unfortunately, a negative result on any of these tests does not guarantee that the dog is “clear.” Note that sulfa drugs and supplements, including sulfa antibiotics, MSM and Deramaxx, may cause false positive results.
“Cystinuria is a particularly frustrating condition to manage,” says San Francisco Chronicle pet columnist Christie Keith, who started a Canine Cystinuria e-mail list and website when one of her Scottish Deerhounds developed cystine uroliths. “A dog known to have cystinuria may go his whole life without obstructing, while another dog, never diagnosed, can have a life-threatening obstruction as his first symptom. It's not known at this time why some dogs with cystinuria form stones and others do not.”
Cystine, like all amino acids, is one of the building blocks of protein. That's why most veterinarians (including many kidney specialists) prescribe a low-protein diet, speculating that reducing cystine supply will reduce the formation of cystine stones. Another common recommendation is to alkalize the dog’s urine because cystine stones form in acid urine.
Unfortunately, says Keith, these strategies are ineffective. “Most of us on the Canine Cystinuria list have found that diet and urinary alkalization have failed to prevent our dogs from forming stones,” she says, “and they have sometimes caused other problems, including other types of stones that form in alkaline urine. If the urine goes into acidity even briefly, cystine stones can form and they won’t dissolve just because alkaline urine is achieved soon after. In addition, feeding ultra-low-protein diets can be dangerous, especially to giant breeds and breeds prone to cardiomyopathy.” (SeeThe Side Effects of Low-Protein Diets below.)
It’s important to provide your dog with extra fluids and frequent opportunities to urinate in order to keep his urine from becoming supersaturated. Salt should not be added to increase fluid consumption for dogs with cystinuria; according to studies conducted on humans, a low-sodium diet may decrease the amount of cystine in the urine.
If urine alkalization is attempted, the target pH is 7.0 to 7.5; higher can predispose dogs to calcium phosphate uroliths. Potassium citrate is preferred for alkalization when needed rather than sodium bicarbonate because sodium may enhance cystinuria.
Cystine stones cannot be dissolved with diet or supplements, but two prescription drugs can help dissolve and prevent them. Cuprimine (d-penicillamine) has potentially serious side effects but is less expensive and more readily available, and many dogs do well on it. According to Keith, Thiola (tiopronin, also referred to as 2-mercaptopropionylglycine or 2-MPG), has fewer side effects, but one of them is the depletion of the owner’s bank account. Maintaining a giant-breed dog on Thiola can cost as much as $500 per month. Because the severity of cystinuria tends to decline with age, the dosage of preventative medications can sometimes be decreased or even stopped.
Dissolution requires a combination of medication, low-protein diet, and urinary alkalinization. Even then it may not be successful or practical for a dog with numerous stones. When it does work, dissolution commonly takes one to three months.
For some dogs, the solution has come not from prevention strategies or medication but from surgery. “It sounds extreme,” says Keith, “but many of us who have stone-forming male dogs with cystinuria have opted for a scrotal urethrostomy. This surgery redirects the dog’s urethra away from the penis to a new, surgically created opening in front of the scrotum.”
The wider opening that results enables males to more easily pass small stones and helps to prevent urinary blockages. “While future obstruction is not impossible,” says Keith, “this procedure reduces the risk substantially.” Still, she cautions, this surgery should not be undertaken lightly. It’s expensive, requiring the expertise of a skilled board-certified surgeon, and because the affected area is rich in blood vessels, there can be significant post-surgical bleeding, though the surgery is not particularly painful.
“The good news,” she says, “is that many dogs, including stone-formers and those who had serious complications when their condition was first diagnosed, have lived not just normal but longer-than-normal lives.”
The remaining three
Like cystine stones, stones composed of xanthine, calcium phosphate, and silica are rare, each representing less than 1 percent of analyzed uroliths. Ironically, they often occur while the patient is undergoing treatment for the prevention of other stones.
Although xanthine is a type of purine, xanthine stones are associated not with diet but with the use of allopurinol, the drug used to treat urate stones as well as canine leishmaniasis. Xanthine crystals almost never occur naturally, though they have been reported in some cats, Cavalier King Charles Spaniels, and Dachshunds. The average age at onset is 6 to 7 years. Like urate stones, they are radiolucent; that is, they cannot be seen on X-rays.
In some cases, discontinuing allopurinol while feeding a low-purine diet has dissolved xanthine uroliths, but in general, treatment consists of surgical removal, urohydropropulsion (a nonsurgical procedure performed with the dog under anesthetic, in which the bladder is filled with saline through a catheter, and the bladder is manually squeezed to force stones out through the urethra), or lithotripsy (the use of high-energy sound waves to break up the stones).
A low-protein diet is usually recommended for dogs receiving allopurinol treatment (to help prevent the formation of xanthine uroliths), but once again what's really needed is a low-purine diet, not restricted protein.
Calcium phosphate stones often develop when the urine is over-alkalized (at a pH greater than 7.5), in an effort to prevent the formation of calcium oxalate, urate, or cystine stones. The average age at onset is 7 to 8 years, but these stones have been found in dogs of all ages, including puppies and seniors.
Calcium phosphate stones are commonly called apatite uroliths, with hydroxyapatite and carbonate apatite the most common. They are radiographically dense, so they are easily seen on X-rays. Uroliths composed primarily of calcium phosphate are rare and associated with metabolic disorders such as hyperadrenocorticism (Cushing’s disease), hypercalcemia, renal tubular acidosis, or excessive calcium and phosphorus in the diet.
Because they cannot be dissolved medically, these stones are usually removed surgically, though that may be unnecessary if the stones are clinically inactive (not growing or causing problems). They have been known to dissolve spontaneously following parathyroidectomy surgery for primary hyperparathyroidism. Unless the patient has a metabolic condition that contributes to calcium phosphate stones, the strategies used for prevention are similar to those used for calcium oxalate stones, although it’s important to avoid excessive alkalization of the urine.
Medications that can enhance calcium excretion, including prednisone and furosemide (Lasix), should be avoided if possible. Salt should not be added to the diet, as sodium increases urinary calcium.
Silica stones are most common in male German Shepherds, Old English Sheepdogs, Golden Retrievers, and Labrador Retrievers, although other breeds and mixed breed dogs have developed them as well. More than 95 percent of silica stones occur in males. The problem can develop in dogs as young as four months or as old as 12 years, but most stones occur in dogs aged 6 to 9 years. Silica stones are radiopaque and can be seen on X-rays. No relationship has been found between urinary pH and silicate urolith formation.
The formation of silica stones is associated with diets high in cereal grains, particularly corn gluten and soy bean hulls, both of which are high in silicates. Corn gluten and soy bean hulls (also called soybean mill run) are ingredients in low-quality prescription diets and dog foods.
Other foods that are high in silica, and which should be avoided, include the hulls of wheat, oats, and rice (hulls are found in whole grains); sugar beets; sugar cane pulp; seafood; potatoes and other root vegetables; onions (which shouldn’t be fed to dogs, anyway); bell peppers; asparagus; cabbage; carrots; apples; oranges; cherries; nuts and seeds; grains; soybeans; and the herbs alfalfa, horsetail, comfrey, dandelion, and nettles. Most of the carbohydrated used in grain-free dry foods, including peas and tapioca, appear to be high in silica. Bentonite clay, a mineral supplement, is also high in silicates.
Because no drug or diet dissolves silica stones, they may be removed surgically, flushed out with urohydropropulsion, or shattered with lithotripsy; no treatment may be required for clinically inactive stones. Silica stones do not usually recur, but it makes sense to feed a diet that is high in protein from animal sources and low in plant foods, including fiber and bran. Canned foods are often higher in protein and lower in plant foods than dry kibble. Some frozen raw and cooked foods do not include vegetables or grains.
As with all stones, keep the urine diluted by increasing fluids and giving the dog frequent opportunities to urinate. Don’t add salt, which is another source of silica.
Dogs who drink water from sources containing sand may develop silica uroliths, so water that contains silica (a primary mineral in sand) should be avoided. In hard-water areas, distilled water is recommended for dogs who form silica stones. Silica stones have also been associated with pica, an eating disorder that causes dogs to eat dirt, rocks, and other non-food items.
Most bladder stones are caused by a single type of mineral. Sometimes a stone consists of two or more minerals in approximately equal proportions, in which case it is called a mixed urolith. These stones are rare, comprising only 2 percent of analyzed uroliths.
A stone that consists of a core mineral surrounded by a smaller amount of a different mineral is called a compound urolith. These make up 10 to 12 percent of analyzed stones. Compound uroliths can sometimes be identified based on differing radiographic density of their stone layers.
Compound uroliths develop when a stone’s environment changes, such as when a struvite stone is treated by reducing urinary pH, magnesium, and phosphorus, resulting in a calcium oxalate shell around the struvite core. Struvite shells caused by infection commonly form over calcium oxalate and other cores, especially since all stones predispose dogs to bladder infections.
One treatment strategy is to try to dissolve the outer layer first. This is especially effective for stones with an infection-induced struvite shell, which make up more than 80 percent of compound uroliths with cores other than struvite. The struvite shell should dissolve with appropriate antibiotic or infection-fighting treatment. X-rays can be used to monitor dissolution. Once the outer shell disappears, treatment strategy switches to the inner core, also called the nucleus, or the stones may then be small enough to remove by urohydropropulsion.
More than half of the compound uroliths analyzed in 2002 by the Minnesota Urolith Center contained a calcium oxalate core, and almost all of these were surrounded by a struvite shell caused by infection. Unlike calcium oxalate uroliths, these compound uroliths were found primarily in female dogs; this is because the female dogs’ anatomy makes them more susceptible to urinary tract infections, which cause struvite stones. Treatment and prevention should be focused on controlling infections and reducing the risk of calcium oxalate stones (see Calcium Oxalate Kidney and Bladder Stones).
Stones with a struvite core made up almost a quarter of compound uroliths, more than half of which were surrounded by a calcium phosphate shell and most of the rest by a calcium oxalate shell. As is common with infection-induced stones, most of these dogs were female.
Urinary acidifiers can contribute to urinary calcium that leads to the formation of calcium-containing stones. Treatment is the same as for struvites: appropriate medication for the infection and possibly a reduced-protein diet short-term to help dissolve the stones quickly. Urinary acidification is not recommended due to the increased risk of calcium oxalate and calcium phosphate formation.
Small percentages (3 to 5 percent each) of compound uroliths were comprised of the following:
- Silica core. Most of these had a calcium oxalate shell and were found in male dogs. Since both silica and calcium oxalate stones are associated with plant-based foods, diets containing substantial plant proteins should be avoided.
- Calcium phosphate core surrounded by struvite or calcium oxalate shells. These are treated the same way as struvite or calcium oxalate stones.
- Urate core. Most of which were surrounded by struvite. Treatment is aimed at controlling the infection along with management of the urate core.
- Compound uroliths with a core or shell of xanthine are treated by discontinuing or reducing the dose of allopurinol.
Sulfa drugs may create a shell around struvite uroliths when used at high doses for prolonged periods, or in dogs with acidic or highly concentrated urine. For this reason, sulfa drugs should be avoided when treating lower urinary tract (bladder) infections, particularly for dogs known to have stones or one of these risk factors.
Preventive treatment should focus on whatever minerals comprised the stone’s inner core. As with all types of stones, increasing fluid intake and opportunities to urinate are recommended. Adding salt to the diet is not recommended, however, as it increases urinary calcium and calcium is commonly found in uroliths.
Once your dog’s stones are successfully treated, you’ll want to use the strategies described here to help keep them from coming back. Stone-forming dogs can be monitored by their veterinarians with X-rays, ultrasound, and urinalyses.
Infection-induced struvites can recur in as little as a few days to a few weeks, while calcium oxalate and silica stones may take a few months to recur. Cystine and urate stones can recur rapidly.
Some dogs continue to form stones despite diet changes and medical therapy. For them the key is monitoring with radiographic imaging (X-rays or ultrasound) at least every 3 to 6 months (more often to start with and for rapidly recurring types) in order to detect stones while they are still small enough to pass through the urethra using urohydropropulsion or catheter-assisted retrieval.A final solution for males with recurring stone blockages is urethrostomy surgery, which redirects the flow of urine to avoid its normal narrow passage.
Without sufficient protein in the diet, protein is pulled from muscles to meet the body’s requirements. Because they are nutritionally inadequate, low-protein diets should never be fed to puppies or dogs who are pregnant or nursing, and they can cause health problems if given to adult dogs for prolonged periods. Hill's u/d is drastically low in protein (dry food has less than 10% protein as fed); Royal Canin SO is also low in protein (14%), though not as bad as u/d. In both cases, the canned varieties have a little more protein than the dry.
According to the Merck Veterinary Manual (9th Edition, 2008), “The signs produced by protein deficiency or an improper protein-to-calorie ratio may include any or all of the following: weight loss, skeletal muscle atrophy, dull unkempt coat, anorexia, reproductive problems, persistent unresponsive parasitism or low-grade microbial infection, impaired protection via vaccination, rapid weight loss after injury or during disease, and failure to respond properly to treatment of injury or disease.”
Ultra-low-protein diets have been linked to dilated cardiomyopathy (DCM) in English Bulldogs, Dalmatians, and other breeds. Dogs with cystinuria, which predisposes dogs to carnitine deficiency even when a normal-protein diet is fed, are particularly at risk. Some Newfoundland dogs are prone to taurine deficiency leading to DCM even when fed regular commercial diets, especially lamb and rice diets, though many manufacturers now add taurine to their lamb and rice diets to help prevent this side effect.
According to a study of cardiac function in healthy dogs fed protein-restricted diets published in the American Journal of Veterinary Research in 2001, “Dogs fed protein-restricted diets can develop decreased taurine concentrations…. The possibility exists that AAFCO [Association Of American Feed Control Officials] recommended minimum requirements are not adequate for dogs consuming protein-restricted diets. Our results also revealed that, similar to cats, dogs can develop DCM secondary to taurine deficiency, and taurine supplementation can result in substantial improvement in cardiac function.”
Low-protein diets are not needed in most cases to prevent the development of kidney or bladder stones. If you choose to feed a low-protein diet, you should supplement with carnitine and taurine to help prevent the development of DCM. Dogs with cystinuria may benefit from supplementation even if fed a regular diet. Suggested preventative dosages are 25 to 50 mg L-carnitine and 5 mg taurine per pound of body weight two or three times a day. For example, a 50-pound dog should receive 1,250 to 2,500 mg L-carnitine and 250 mg taurine twice or three times a day. Higher dosages are needed to treat DCM.You can also add eggs and dairy products to a low-protein diet for dogs with hyperuricosuria to increase protein. Dogs prone to forming calcium oxalate stones will benefit from added protein from meat, poultry, eggs, liver, and dairy, none of which are high in oxalates.
We use different ranges of low, moderate, and high purines for plant and animal foods because if you restrict the amount of purines that come from plant foods as much as possible, that allows you to feed small amounts of moderate-purine meats while still keeping the total purine content of the diet low.
The foods that are highest in purines are organ meats such as liver, kidney, heart, and sweetbreads (thymus glands), as well as baker’s and brewer’s yeast. Vitamin supplements containing glandular substances and yeast are best avoided. Theobromine, the alkaloid that makes chocolate toxic to dogs, is extremely high in purines.
Foods that can be fed in moderation include muscle meat, such as beef, lamb, and poultry, and some vegetables. Cooked foods are slightly higher in purines than raw, likely due to the loss of fat and moisture.The purine levels of fish vary from moderate to high.
Eggs and dairy products contain almost no purines and can be fed in any amount. Fruits, nuts, and honey are mostly low in purines, with the exception of peanuts, which are really a legume (peanut butter is considered OK to feed). Whole grains have more purines than most cereals (oatmeal is in between and should be fed only in moderation). Most vegetables are low in purines, but green peas, dried peas and beans, spinach, asparagus, and cauliflower should be fed in moderation.
Some sources say that the purines from plant foods are not readily converted to uric acid and therefore may not be a problem for dogs prone to forming urate stones, but I have not been able to verify that.
The numbers following each food show the milligrams of purines and/or the milligrams of uric acid produced per 100 grams (about 3.5 oz). Ranges indicate values found from different sources, or for different parts. In a few cases, we were not able to find actual values but only indications as to whether the foods are considered low (less than 50 mg purines or 100 mg uric acid), moderate (50-150 mg purines; 100-400 mg uric acid), or high (more than 150 mg purines or 400 mg uric acid).
Note that there is limited information on the purine content of foods. For example, we found only one source for lamb liver, from 1976. Although this food appears to be low enough in purines to feed occasionally, it is probably safer to follow the rule to avoid organ meats rather than rely on this particular type of liver being low enough in purines to feed.
RED: High in purines, avoid (more than 200 mg for animal foods; more than 50 mg for plant foods)
YELLOW: Moderate purines, feed sparingly (50-200 mg for animal foods; 25-50 mg for plant foods)
GREEN: Low in purines, safe to feed (less than 50 mg for animal foods; less than 25 mg for plant foods).
|EGGS & DAIRY PRODUCTS|
|Cheese||6 – 8||6 - 9|
|Cottage cheese / ricotta cheese||0 – 10||0 - 9|
|Yogurt (plain)||0 – 9||0 - 8|
|MEAT & POULTRY|
|Calf sweetbread (thymus gland)||525||1260|
|Beef (calf) spleen||343||444|
|Beef (calf) liver||182 – 231||460 - 554|
|Beef kidney||112 - 213||218 - 269|
|Chicken liver||236 - 243||243|
|Pork liver||125 - 289||300 - 515|
|Beef heart||107 - 171||256|
|Beef muscle meat||58 - 90||110 - 140|
|Chicken muscle meat||94 – 179||110 - 300|
|Duck||64||138 - 153|
|Lamb muscle meat||76 - 127||182|
|Ham||83||131 - 198|
|Pork muscle meat||63 - 119||120 - 280|
|Rabbit||60 - 71||105 – 170|
|Turkey||50||120 - 150|
|Venison||67||105 – 160|
|FISH / SHELLFISH (fresh or canned)|
|Anchovies||108 - 411||239 - 260|
|Herring||67 - 91 (378?)||160 - 219|
|Mackerel (canned is highest?)||60 - 246||95 - 400|
|Salmon||68 – 250||110 - 250 (avg 170)|
88 – 480
|210 - 480|
|Shrimp||61 - 234||147|
|Carp||63||150 - 160|
|Clams||52 – 136|
|Cod||63||109 - 150|
|Haddock||54 – 193||130 - 139|
|Halibut||123||178 - 294|
|Lobster||73||60 - 175 (avg 118)|
|Mussels||154||112 - 370|
|Oysters||38 - 107||90|
|Pike / perch||46 - 58||110 - 140|
|Trout||83||200 - 297|
|Tuna||107 - 142||257 - 290|
|White fish||116 – 129|
|Beans, garbanzo (chickpeas)||56||109|
|Beans, legumes (not green beans)||144 – 230|
|Beans, white||75 - 202||180|
|Lentils||222||127 (dry weight)|
|Peas||62 - 195||84 - 150|
|Soybeans||92||190 - 220 (dry weight)|
|Asparagus||10 (75?)||23 - 25|
|Tofu||29||68 - 70|
|Beets||8||19 - 20|
|Broccoli||21||50 - 81|
|Brussels sprouts||25||60 - 69|
|Cabbage||10 - 21||22 - 40|
|Carrots||6||15 - 17|
|Cauliflower||19||45 - 51|
|Cucumber||2||6 - 7|
|Eggplant||8 - 21||20|
|Green beans||18||20 - 43 (avg 37)|
|Green Pepper||4||10 - 55|
|Kale||13||30 - 48|
|Lettuce||4||10 - 13|
|Potato||6||15 – 18|
|Spinach||21||50 - 57|
|Summer squash (e.g., zucchini)||8||20 - 24|
|Winter squash (butternut, acorn, etc.)||(low)|
|Peanuts||42||79 - 100|
|Almonds||13||30 - 37|
|Apple||6||14 - 15|
|Apricot (dry is higher)||8||20|
|Avocado||13||19 - 30|
|Banana||11||25 - 57|
|Bilberry, blueberry, huckleberry||8||20 - 22|
|Orange||8||19 - 20|
|Strawberries||11||21 - 25|
|GRAINS, CEREALS, GRASSES, SUPPLEMENTS|
|Barley||34||82 - 96|
|Bread, whole grain||35||84|
|Millet||35||62 - 85|
|Oats||42||94 - 100|
|Rice, Brown||(moderate 50-100)|
|Bread (not whole wheat)||12 - 16||14|
|Egg Noodles||22||40 - 52|
|Pasta, whole wheat (cooked)||21||50|
|Rice, white (cooked)||6 - 10||25|
|Rye||20||47 - 51|
|Wheat flour||8 - 12||20|
|Wheat, whole grain||17||40 - 51|
British Kennel Club Registers First LUA Dalmatian
Published in the Whole Dog Journal in June 2010.
In January 2010, the Kennel Club (Britain’s equivalent of our American Kennel Club) accepted the registration of its first LUA (Low Uric Acid) Dalmatian dog, despite protests from breed clubs.
As explained in Urate or purine stones above, Dalmatians carry a genetic mutation that predisposes them to the formation of life-threatening urate bladder stones. It is not unusual for Dalmatians to need several surgeries to remove stones during their lifetimes. Feeding a low-purine diet helps prevent urate stones, but the problem can be so severe that in some cases the only option is euthanasia. Genetic testing has shown that there are no longer any AKC-registered Dalmatians in the US (or likely any dogs registered by the Kennel Club in the UK) that carry the normal gene.
In 1973, Bob Schaible, PhD, a geneticist and breeder of Dalmatians, crossed a Dalmatian with a champion Pointer, a similar breed thought to be closely related to the Dalmatian. His goal was to produce offspring who look like purebred Dalmatians but carry a normal gene for uric acid production. The breeding was successful from a health standpoint, though the new Dalmatians’ spots were smaller and less defined than usual.
The offspring and their descendants were backcrossed to purebred Dalmatians for many generations, resulting in dogs that are indistinguishable from purebred Dalmatians. In 1981, Dr. Schaible, with the approval of the Dalmatian Club of America’s board of directors, was granted AKC registration for two dogs from the fourth generation of the backcross. However, when the Dalmatian Club’s general membership found out and caused an uproar, the AKC refused to register any offspring from these dogs. There has been no policy change since that time – in fact, the Dalmatian Club banned any discussion of the topic for 22 years. In 2006, the membership was polled again, and a majority supported continuing the testing and breeding of backcrossed Dalmatians, but in 2008, the membership again voted against registering these dogs. As a result, all AKC-registered Dalmatians remain affected by the defective gene that causes high uric acid. Despite this, Dr. Schaible has continued his Dalmatian Low Uric Acid Project or Backcross Project, breeding to the best lines of Dalmatians. The offspring are now 14 generations removed from the single Pointer outcross and more than 99.98 percent of their genes are identical to those of purebred Dalmatians. Many of these dogs are registered with the United Kennel Club (UKC) in the US.
The British television show Pedigree Dogs Exposed, which aired in August 2008, called attention to genetic problems affecting some breeds. The program resulted in ongoing changes in breed standards and judging, as well as a commitment from the Kennel Club to consider registering dogs from out-crossings and inter-variety matings if doing so may contribute to the breed’s health. In keeping with these changes, the Kennel Club now registers LUA Dalmatians, subject to certain conditions, including examination by qualified judges to confirm that their appearance meets breed standards.
The AKC’s stance as of 2002 is that a two-thirds supermajority of a breed club’s membership must approve before it will consider opening the breed’s stud book. It’s time for the AKC to take the lead in improving the health of purebred dogs – and for breed fanciers to put the health of their dogs above an insistence on genetic purity.
Update: The first registered LUA Dalmatian is winning big: see Fab Fiona does it again. However, her offspring cannot be exported to other countried in Europe eager to include them, see Fiona the Dalmatian - the ongoing battle (1/18/12).
Published in the Whole Dog Journal in January 2011.
A few months ago, I wrote about the British Kennel Club’s registration of two special Dalmatians over the objections of the breed clubs there (WDJ June 2010). These two dogs were the result of a breeding project begun in 1973, in which a single outcross to a Pointer was made in order to reintroduce the normal gene for uric acid back into the Dalmatian bloodline.
Fourteen generations later, more than 99.98 percent of the offspring’s genes are identical to those of a purebred Dalmatian. The one critical exception is that, unlike every other dog registered by both the British and American Kennel Clubs, these dogs are no longer at risk of forming urate bladder stones, a painful and potentially deadly condition caused by a genetic mutation carried by all Dalmatians.
Since that article was written, there have been some new developments. First, an update on what has been happening in Britain: Fiona (Fiacre First and Foremost), the first low uric acid (LUA) Dalmatian registered with the Kennel Club, has been winning at shows. While naysayers claimed her first win was “fixed,” Fiona’s group win the following week proved that these dogs are indistinguishable from other Dalmatians, and worthy of inclusion in breeding programs.
Meanwhile, back here in the States, theAmerican Kennel Club (AKC) Health & Welfare Advisory Committee submitted a report with the following recommendation:
“Because the introduction of the low uric acid dogs into the AKC registry gives Dalmatian breeders a scientifically sound method of voluntarily reducing the incidence of the condition, this committee strongly r e commends some controlled program of acceptance of these dogs. Where the strict health and welfare of the breed is the overriding concern, no other argument can be made.”
Despite these findings from its own committee, the AKC board voted in November to defer a decision until after June 2011, when a vote of the Dalmatian Club of America’s membership would be held. Since the breed clubs in both Britain and the U.S. have remained staunchly opposed to registration of LUA dogs, it seems unlikely that this vote will show them putting the welfare of their breed above their concerns of genetic purity. While AKC says it will “consider this vote, along with other factors in reaching its final decision,” don’t hold your breath in hopes that they will do the right thing.
In the meantime, another dog has paid the ultimate price for the breeders’ shortsightedness. Armstrong, a seven-year-old Dalmatian who worked as a therapy dog at the children’s cancer unit at the Primary Children’s Medical Center in Salt Lake City, Utah, was put to sleep due to uncontrollable urate stones.
Armstrong had previously undergone multiple surgeries to remove stones, followed by a urethrostomy, where the dog’s urethra is rerouted away from the penis to a new, surgically created opening. Even after such a drastic measure, Armstrong continued to form stones, requiring two more surgeries just five months apart.
His owner, Shelley Gallagher of Sandy, Utah, had been feeding Armstrong a low-purine diet, giving him extra fluids to help dilute his urine, letting him out to urinate every few hours (including every night at 2 am), and obsessively monitoring him – all, ultimately, to no avail.
If you’d like to let the Dalmatian Club of America know how you feel about this, email its president, Meg Hennessey, at email@example.com. For those interested in LUA Dalmatians, they are currently registered in the U.S. only with the United Kennel Club (UKC).
- The AKC Canine Health & Welfare Advisory Committee Executive Summary & Recommendation – LUA Dalmatians
- Minutes from the AKC Board of Directors meeting held November 8-9, 2010
- November 2010: And the AKC's decision re accepting the spotted mongrels is... for an update in November, 2010, on what AKC is (not) doing about the situation.
- January 2011: Dalmatian Club argues against admitting LUA Dalmatians.
- July 2011: The Dalmatian Club of America has voted 305 to 253 against to accept the low-uric acid (LUA) Dalmatians, paving the way for AKC registration. See We are Dal-lighted! for details.
- Calculi (the plural of calculus)
- urinary stones.
- the appearance of crystals in urine.
- surgical opening of the bladder to remove uroliths.
- blood in the urine, a symptom of urinary stone disease.
- the excretion of uric acid leading to urate stone formation.
- a nonsurgical procedure that uses shock waves to break up stones so they can be flushed out with urine.
- a strongly acidic glycoprotein present in normal urine, which inhibits calcium oxalate crystal growth.
- kidney stones.
- excessive accumulation of oxalate in the body because of kidney failure.
- a surgical procedure that redirects the dog’s urethra away from the penis to a new opening in front of the scrotum.
- Urinary tract stone disease
- also called urolithiasis, urinary stones, ureteral stones, bladder stones, urinary calculi, ureteral calculi, or urinary calculus disease.
- a nonsurgical procedure in which the bladder is filled with saline through a catheter, and the bladder is squeezed to expel stones through the urethra.
- aggregates of crystalline and occasionally noncrystalline solid substances that form in one or more locations within the urinary tract.
As noted in our previous articles, an accurate diagnosis is essential because what prevents or treats one type of stone may actually cause another. The only way to be sure of a stone’s identity is to have it analyzed. Your veterinarian, however, can make an educated guess based on urinary pH; the dog’s age, breed, and sex; the identification of urinary crystals; radiographic (X-ray) density; whether infection is present; and certain blood test abnormalities.
When should your veterinarian become involved? As soon as you notice symptoms or, if your dog’s breed is strongly predisposed to developing stones, even sooner. Not all bladder and kidney stones are dangerous; some are flushed during urination while still small in size and others remain unnoticed in the kidney or bladder. Stones don’t create complications until they interfere with urination. It’s important to become familiar with urinary stone symptoms, which include straining to urinate, blood or pus in the urine, painful or difficult urination, increased frequency of urination, the passage of small amounts of urine, licking the genitals more than usual, “accidents” in house-trained dogs, or discomfort in the lower back.
A dog who strains and then releases a flood of urine may have just passed a stone and should be examined. If you can find the stone, take it with you so it can be accurately identified. A dog who is unable to urinate needs immediate medical attention because a plugged urethra can cause urine to back up into the system, resulting in a ruptured bladder or kidney failure. A bladder that has been stretched can lose muscle tone, making it difficult to empty completely, which can lead to infection or more stones. Bladder stones are much less likely to cause an obstruction in female dogs than in males, thanks to the shorter and wider urethra in females.
Increasing urine volume and opportunities to void urine are important factors in preventing uroliths of all types. The more a dog drinks and the more frequently he urinates, the less concentrated his urine and the less likely the formation of crystals that can become stones. Encourage your dog to drink more by adding water to his food and offering flavored water in addition to plain. For dogs with urate stones, you can add salt to food to increase thirst (start with a pinch, watch your dog’s response, and add more in small steps until your dog drinks more water), but added salt should be avoided for dogs prone to forming cystine, calcium phosphate, or silica stones.
Be sure that your dog has frequent opportunities to urinate because when dogs have to hold their urine for extended periods, their urine is more likely to become supersaturated, at which point its minerals begin to precipitate out as crystals.
Minnesota Urolith Center at the University of Minnesota College of Veterinary Medicine (no charge to analyze stones or urine sediment).
- The Dalmatian Club of America, Information on Urinary Stones & Treatment
- Canine Hyperuricosuria DNA Test, UC Davis Veterinary Genetics Laboratory
- Preventing Urate Stone Formation In Dalmatians Using A Basically BARF Diet
- Various food types and their purine content
- Normal Uric Acid Dalmatians
- The Dalmatian Heritage Project
- Cystinuria Yahoo Group
- Canine Cystinuria (also see this summary article)
- Cystinuria in Mastiffs
- Cystinuria DNA and Nitroprusside Tests
, a Dalmatian breeder, sells pH test strips in the range of 5.0-10.0 in 0.5 increments. Here's what she writes:
I have bulk purchased the Merck brand of pH test strips and am keeping them in stock. This way I've been able to keep the price down to a reasonable level (instead of the $45 and $55 which others have been paying for the same thing). There are 100 test strips to the package. According to the company shelf life is indefinite unopened and refrigerated and once opened a mere ten years.
One package - $19; Subsequent packages in the SAME order $18 -- this includes packaging and shipping costs.
These prices assume that you live in the United States. I am able to accommodate purchasers from almost all countries (except just one or two third world countries). If you live outside the US, please email me with your location and I will have to check with the bank (they sometimes charge to cash non-US checks) and with the postal service for the cost of shipping. Thus far the additional cost for those living outside the US has not exceeded $3.00US extra for each order (thus ordering more than one package spreads out those extra fees) and it has still been cheaper than getting the same product through the local veterinary.
I also accept payments through Paypal. However, you will need to voluntarily add $1.75 per package in your order to cover the fee that is charged by Paypal (assuming you live in the United States). My name under Paypal is AtoZDals, just as in my email address.
Include your full name and address with your payment and make checks out to me. Snail Mail to:
827 Boulevard Road SE
Olympia, WA 98501
Studies: Dr. Joe Bartges at the University of Tennessee College of Veterinary Medicine is conducting a number of ogling studies involving different types of urinary stones. If you have a known stone-forming dog and might be interested in participating, see Clinical Studies for more information.
Minnesota Urolith Center at the University of Minnesota College of Veterinary Medicine
- Canine Urate Uroliths
- Canine Cystine Uroliths
- Canine Calcium Phosphate Uroliths
- Canine Silica Uroliths
- Management of Mixed or Compound Uroliths Containing Calcium Oxalate or Struvite in Dogs
General Information on Urinary Stones:
- Canine uroliths: Frequently asked questions and their answers
- Stalking stones: An overview of canine and feline urolithiasis
- Nutritional Management of Canine Urolithiasis (Stevenson, Rutgers) from the Encyclopedia of Canine Clinical Nutrition
- Canine Urolithiasis (Merck Veterinary Manual)
- Improving management of urolithiasis: therapeutic caveats
- Use of laser lithotripsy to treat urocystoliths in dogs: current status
- Interpreting and Managing Crystalluria, Kirk's Current Veterinary Therapy XIV, 2009.
- Management of Cystic and Urethral Calculi in Male Dogs
- Analysis of 36,032 canine cases shows decline in struvite uroliths
- Canine urolithiasis: A look at over 16 000 urolith submissions to the Canadian Veterinary Urolith Centre from February 1998 to April 2003
- Perspectives: Analysis of 275,000 uroliths
- Current Trends in Urolith Submissions in Canada
- Information on Urinary Stones & Treatment from the Dalmatian Club of America
- Fallacy of "Low Protein" vs. "High Protein"in Generalizing About Diets For Stone-Forming Dalmatians
- Nutrition and Urolithiasis
- Urate Urolithiasis
- Nutritional Management of Uroliths
- Normal Uric Acid Dalmatians
- The Dalmatian Heritage Project
- Purines in Foods:
- Various food types and their purine content (amounts shown are uric acid, not purines)
- Purine Metabolic Patients’ Association
- Purine Content of Foods
- List of Diet/Food Sources High or Low in Purine Content
- Bowes & Church's food values of portions commonly used (Google books)
- Gout - Foods to Avoid
- Tufts Medical Center - Low Purine Diet
- Portosystemic Shunts:
- Canine Cystinuria
- Cystinuria in Mastiffs
- Cystinuria in Scottish Deerhounds
- Update on Cystinuria (Challenges to understanding cystinuria in dogs that are not Newfoundlands)
- Cystinuria in Newfoundland Dogs
- PennGen Laboratories
- Tiopronin (brand name Thiola), also called 2-mercaptopropionylglycine (2-MPG):
- D-penicillamine (brand names Cuprimine, Depen)
Calcium Phosphate uroliths:
- Canine calcium phosphate uroliths. Etiopathogenesis, diagnosis, and management
- Association between hyperadrenocorticism and development of calcium-containing uroliths in dogs with urolithiasis.
- Compound Uroliths: Treatment and Prevention, Kirk's Current Veterinary Therapy XIII, 2000.
- How to simplify management of complex uroliths
Carnitine and Taurine Deficiency:
- Link between low-protein diets fed to dogs with cystine or urate stones and dilated cardiomyopathy (DCM)
- Evaluation of Urinary Carnitine and Taurine Excretion in 5 Cystinuric Dogs with Carnitine and Taurine Deficiency
- Effects of dietary fat and L-carnitine on plasma and whole blood taurine concentrations and cardiac function in healthy dogs fed protein-restricted diets
- Idiopathic dilated cardiomyopathy in Dalmatians: nine cases (1990-1995)
- Effects of dietary fat and carnitine on urine carnitine excretion in healthy dogs
- Taurine Deficiency in Newfoundlands fed commercially available complete and balanced diets
- Chronic Heart Failure in Dogs
If you have any questions or comments, you can contact me, but I have less time to answer questions than I used to, and it may be several days to a week before I can respond. My name is Mary Straus and you can email me at either or