Some breeds are more susceptible to this than others. Here’s what you need to know about protecting your best friend from urate stones.
Good urinary tract health is crucial to your dog’s overall well being, happiness and longevity. A number of issues and diseases can affect this part of his “plumbing”, and among these are several types of uroliths, commonly referred to as “stones”. They develop in the urinary tract – primarily the bladder – of some dogs. In this article, we’ll focus on just one type of urolith – urate stones, also known as uric acid stones (“urate” and “uric acid” are different terms for the same thing).
Which dogs are susceptible?
Two types of dogs are prone to developing urate stones: those with liver shunts, and those with a genetic predisposition.
- A liver shunt is a condition in which blood flow to and through the liver is compromised. It causes blood from the intestinal tract to bypass the liver and fl ow directly into the systemic bloodstream. This prevents the by-products from digested and absorbed food from being processed by the liver and removed from circulation. So the by-products remain in the bloodstream and can adversely affect some animals.If your dog has a liver shunt, you should proactively perform urine checks for urate crystals (I’ll explain how to do this a little later). This is an important step in preventing crystals from forming into stones.
- Some breeds are genetically predisposed to urate uroliths, and 80% of these are Dalmatians. Other breeds with a predisposition to these stones include bulldogs and black Russian terriers. A DNA test is available that can tell you (or your veterinarian) if your dog is carrying one or two copies of the gene that contributes to the formation of urate stones (UC Davis Veterinary Genetics Laboratory). Dogs with two copies of the gene carry the dominant gene and are automatically predisposed. This is good information to have if your dog happens to be one of the high-risk breeds, or has one of these particular breeds in his ancestry.
Where do urate stones come from?
Urate stones are formed from foods that contain purines. These natural substances are a component of DNA – and DNA is found in high concentrations in common protein sources. Some types of proteins contain more purines than others. Organ meats have the highest purine content, and vegetable and dairy proteins have the lowest.
Purines break down into uric acids in the liver. Metabolic processes performed by liver cells convert the uric acid to a water soluble substance called allantoin, which passes from the kidneys to the bladder and is excreted in urine. At least, this is the physiologic process that occurs in a normal, well functioning body.
In Dalmatians and other predisposed breeds, however, the last step in the process doesn’t take place. Purines are broken down into uric acid, but the liver isn’t able to convert it to allantoin. The “untreated” uric acid passes into the kidneys, but because it isn’t water soluble, uric acid crystals can accumulate in the kidneys and move into the bladder. When these crystals cohere, a stone forms.
Urate stones can be a medical emergency for your dog, because if they grow large enough they can block the fl ow of urine entirely. The inability to pass urine is a life-threatening situation.
What are the symptoms?
- Urate crystals can be very irritating to a dog’s kidneys and bladder, and can trigger urinary tract infections. Symptoms of possible uric acid crystals or stones include:
- Straining and/or discomfort during urination
- Blood in the urine
- Passing only small amounts of urine
- Urine leakage accidents around your home
- Drinking and urinating more
If your dog is a Dalmatian or other high-risk breed or mix, and you suspect he may have crystals or stones, it’s important to ask your veterinarian to collect a urine sample immediately to check for signs of a problem.
Again, urinary blockage is a medical emergency, but it your dog has crystals or a stone that isn’t completely occluding the urethra and making it impossible to pass urine, the situation can often be managed with medication and dietary adjustments.
Why is a neutral urine PH important?
The first goal in managing uric acid crystals or stones is to dilute the urine by increasing water intake. The second is to create a neutral urine pH, neither too acidic nor too alkaline. Alkaline urine can contribute not only to uric acid crystals and uroliths, but also to cystitis (irritation of the bladder lining of the bladder). You want to get and keep your dog’s urine pH at 7.
I recommend you purchase pH strips at the local drug or health food store and check your dog’s urine pH at home, to keep it balanced at 7. This is a great way to be proactive in helping prevent crystals and stones from forming. It’s best if you can hold a strip into the stream as your dog urinates, but you can also collect it in a cup and dip the pH strip in the sample. Just make sure to test the sample immediately to get an accurate reading. Always check pH in the morning, before your dog eats breakfast. Checking after meals isn’t accurate as pH shifts after food intake.
Note that urate crystals are found naturally in the urine of Dalmatians, so if you have a dog of this breed, it doesn’t mean he’ll automatically develop a bladder stone. However, in any other breed of dog, urate crystals in the urine are not normal and should be addressed immediately.
Avoid these triggers
Dogs with a history of urate stones should avoid food, snacks and treats with high vitamin C content. Vitamin C acidifies the urine and can precipitate the formation of urate crystals and stones. Also eliminate the following:
- Brewer’s yeast, wheat germ
- Mushrooms, asparagus, cauliflower
- Shellfish, sardines, cod, herring and haddock
- Organ meats (liver, kidney)
How are urate uroliths treated?
A moisture-rich diet creates more dilute urine and is therefore critical to preventing or avoiding a recurrence of crystals or stones. A low-purine diet in combination with infection management is often effective at dissolving existing urate stones, but it can take a few weeks to several months for the stones to completely disappear.
Stones located in the urethra or the ureters (the tubes that connect the kidneys to the bladder) typically must be surgically removed along with any other stones that don’t dissolve despite dietary changes and medical management.
Surgery to remove a bladder stone is known as a cystotomy. Depending on the patient and the location and size of the stone, other less invasive procedures might be appropriate. These include a technique called laser lithotripsy, which breaks down stones into smaller pieces that can then be voided out. A procedure called voiding urohydropropulsion, meanwhile, involves manually expressing stones out through the urethra while the patient is sedated.
If your dog has been diagnosed with urate stones, it’s imperative that you continue treatment until the condition is resolved, and then incorporate a proactive prevention plan to avoid recurrence. A urinalysis should be completed monthly until the situation is normalized, and then every three to six months to ensure your dog isn’t brewing more crystals.
How can you prevent the problem?
Dogs predisposed to developing uric acid crystals or stones should eat a low purine diet, preferably raw, or at least canned for increased water content in the food. Many veterinarians assume a low purine diet means a low protein diet, since most foods high in protein are also high in purines. This has led to the common practice of putting urate-prone dogs on a vegetarian diet. However, a long term protein-deficient diet leads to a host of other medical issues for dogs. In my opinion, a better approach is to feed a balanced, low-purine, species-appropriate diet that supplies a sufficient amount of animal protein and a moderate amount of fat. Ideally, a customized, homemade diet would be best, allowing the guardian to choose exactly what ingredients are included. A more convenient option many people prefer is to start with a dehydrated fruit and veggie base (such as The Honest Kitchen’s Preference or Sojo’s Grain Free Dog Food Mix) and add eggs, protein and healthy fat (coconut oil).
In addition to regularly checking your dog’s urine pH at home, get a urinalysis done at least yearly if your dog has a liver shunt or you have a high-risk breed. This will allow your veterinarian to check for urine sediment and determine if crystals are present. If they are, you can address the situation immediately with dietary modifications that will reduce the likelihood of bladder stones, and keep your dog feeling good.