What food causes bladder stones in dogs?

Bladder stones are exactly that, stones that form in your pet’s bladder. The more technical term is urolithiasis, which denotes the presence of uroliths in the urinary tract. These stones can develop over weeks or months, and a common question we are asked here at My Pet Nutritionist is whether dietary changes can make a difference.

We thought we’d focus on what bladder stones are, the different types and whether in fact dietary management is something to consider.

What Are Bladder Stones?

Cats and dogs can be prone to developing urinary stones and infection. These occur when the concentration of certain minerals in your pet's urine becomes too high (alkaline). In healthy pets, the urine pH is generally in the 6.5 to 7.0 range. If the pH is acidic (pH below 6) or alkaline (pH above 7) it may allow bacteria to thrive and for crystals or stones to form.

Stones in the bladder can cause inflammation, predispose to urinary tract infections, and even cause an obstruction of the urinary tract.

There are several different types of stones, and they are composed of different minerals and compounds:

-          Struvite,

-          Calcium oxalate,

-          Urate,

-          Cystine,

The most common causes include:

-          Bacteria in the urinary tract,

-          Urinary pH,

-          Minerals present in the urine,

-          Genetics,

-          Bladder inflammation.

Struvite Stones

These stones form due to excess magnesium, ammonium and phosphorus. 

Normal canine urine is slightly acidic and contains waste products from metabolism.  Struvite is a normal compound found in canine urine and will remain dissolved as long as the urine is acid and not too concentrated.  When the urine become too concentrated or alkaline, struvite crystals form. 

These stones tend to form as a result of a urinary tract infection and involves an enzyme known as urease. 

Urease is produced by the pathogenic bacteria and breaks down urea, which is normally found in urine.  In the process, excess ammonia is produced which causes the urine to become alkaline.  Excess ammonia in the urine also results in bladder inflammation, contributing to the issue. 

These stones are generally more common in female dogs. 

Kidney disease, long term use of diuretic medication and PPI’s can also result in alkaline urine, predisposing the dog to struvite stones.

Calcium Oxalate Stones

The current line of thinking is that urine high in calcium, citrates, or oxalates and is acidic predisposes a dog to developing calcium oxalate urinary crystals and stones.

Recent studies have shown diets that cause high urine acidity (urine pH less than 6.5) may predispose dogs to develop this type of bladder stone.

But, like most things, there are likely other causes of calcium oxalate bladder stones too.  For example, over-usage of antibiotics may reduce numbers of the intestinal bacteria Oxalobacter formigenes whose sole nutrient is oxalate. In dogs with low populations of Oxalobacter, excess oxalate is secreted in the urine, increasing the likelihood that calcium oxalate crystals and stones can form if the urine is highly concentrated or becomes acidic.

Calcium oxalate uroliths are noted more commonly in male dogs and the breeds most diagnosed with both struvite and calcium oxalate bladder stones included Shih Tzus, Miniature Schnauzer, Bichon Frise, Lhasa Apso, and Yorkshire Terrier.

Urate Stones

Urate stones are generally caused by a genetic condition in some dog breeds like Dalmatians, Jack Russel Terriers and Bulldogs. But they are also seen with liver disease, especially in dogs or cats with liver shunts.

Urate stones are made from compounds called purines.

Purines are one of the most common chemical compounds on the planet.  There are both endogenous and exogenous.  Exogenous purines are absorbed by the body through the foods eaten, and endogenous purines are made by the body itself.

Purines and pyrimidines are the two families of nitrogenous base that make up nucleic acids – in short, they are the building blocks of DNA and RNA.

Purines have a number of functions in the body:

-          Signalling molecule,

-          Provide energy,

-          Control cell growth,

-          Part of essential coenzymes,

-          Contribute to nervous system function (including neuronal development).

As you can see, purines perform many important functions in the cell, and so the balance between its synthesis and degradation is essential. 

When purines are catabolised, the result is uric acid.  In all other mammals, apart from humans and Dalmatians, uric acid is then converted to allantoin, which is a very soluble excretion product.  For us humans and those unlucky dogs, we excrete uric acid through the kidneys (with some excreted through the gastrointestinal tract). 

Uric acid is suggested to behave as a potent antioxidant. It is also thought to maintain blood pressure under low salt conditions and has been seen to function as an anti-inflammatory in certain diseases, but when levels become too high, in a condition known as hyperuricemia, problems can ensue. In humans, this can result in diseases such as kidney stones and gout and may cause hypertension. In those unlucky dogs, high uric acid levels result in bladder stones.

For this reason, a low purine diet is often suggested for those pets suffering urate stones. 

Foods High in Purines

-          Organs/offal (brain, heart, liver, kidneys)

-          Wild or Farmed Game

-          Herring

-          Mackerel

-          Trout

-          Sardines

-          Sprats

-          Legumes (such as kidney beans, lentils, chickpeas)

Foods Lower in Purines

-          Green leafy vegetables (except spinach)

-          Eggs

-          Nuts

-          Muscle meats from chicken, turkey, lamb, pork, beef,

-          Fruits

If urate stones are associated with liver disease, you may want to learn more about liver disease in our other blogs.

Liver Disease

Liver Shunts

Foods to Feed in Liver Disease

Cystine Stones

This is rarer in the dog, but it can occur.  This is when bladder stones are composed of cystine crystals, and it is largely genetic.

They are more commonly found in the following breeds:

-          Mastiff,

-          Saluki,

-          Puli,

-          Basset Hound,

-          Dachshunds,

Findings Here

Cystine is an amino acid that is freely filtered in urine and almost completely reabsorbed by the kidney tubules. Sadly, an inborn error of metabolism causes high concentrations of urinary cystine in those affected dogs.

These stones also form in acidic environments and in concentrated urine.

As you can see, it’s never quite as simple as “my dog has bladder stones!”  There are a number of different types and a number of causes. 

It’s essential to start with the basics and promote optimal urinary health in our dogs:

The Ultimate Natural UT guide for Pets

In addition to this, ensure you dog is drinking plenty of water to avoid concentrated urine (it’s easy to see how this occurs in a low moisture diet i.e. dry). 

For the rest, it really is important to get to the bottom of the type of bladder stone and what may be driving its formation.  Dietary modification has some great successes so if you would like some support and guidance, please check out our services.

Thanks for reading,

Lisa

Bladder stones are common in dogs. They are the result of one or more underlying abnormalities, making stone analysis a critical step in the diagnostic process. It is also be important to evaluate what the dog was fed before the bladder stone diagnosis and analyze blood and urine for clues as to how nutrition may aid in preventing bladder stone recurrence.

Bladder stones set the stage for chronic urinary tract infection, and some bladder stones (struvites) grow more quickly if the dog already has a urinary tract infection. Consequently, urinary tract infection and bladder stones commonly occur together. Therefore, your veterinarian will recommend long-term antibiotics to kill bacteria on an ongoing basis while the bladder heals from surgery and the bladder lining returns to normal. Resolving or controlling bladder infection is one important way to prevent recurrence of bladder stones.

Is there any chance that bladder stones can be dissolved rather than resorting to surgery?

The opportunity to dissolve bladder stones in dogs, called dissolution, depends on the composition of the stones. Unfortunately, the most effective way to know the composition of a canine bladder stone is to remove one and have it analyzed. That said, it may be possible to draw some conclusions about the composition of a bladder stone based on crystals identified during the urinalysis. Also, it may be possible to retrieve a small bladder stone for analysis via a urethral catheter.

Your veterinarian will work closely with you to determine if attempting medical dissolution is a reasonable option for your dog. In most cases, surgical removal of bladder stones is the treatment of choice. Surgery provides the following benefits:

• prevents blockage of urine outflow, which is a true emergency.
• relieves the dog of the discomfort of stones in the bladder.
• allows bladder healing to begin.
• allows for definitive analysis of the stone(s), which provides the best opportunity to prevent recurrence.

How will I know what steps I need to take and what I need to feed my dog in order to prevent his bladder stones from recurring?

The nutritional focus for a particular dog will depend on the specific diagnosis that dog receives, and your veterinarian is a key partner in creating an overall plan that best fits your dog's bladder stone composition. There are, however, some general statements that can be made about the nutritional management of bladder stones that occur in dogs:

• Purine stones. Dissolution may be possible with appropriate protein-restricted therapeutic nutrition combined with measures to increase urine production (diuresis), creating an alkaline urine pH, controlling/eliminating any existing urinary tract infection, and giving a medication called allopurinol (brand name Zyloprim®). This is the same plan to prevent recurrence.
• Calcium oxalate stones. Dissolution has not proven to be effective, so the nutritional focus is designed to prevent recurrence. Goals include reducing dietary calcium in order to reduce the calcium excreted in the urine, reducing oxalic acid in the urine, inhibiting calcium oxalate crystal growth, and reducing urine specific gravity (concentration). Diets that may help include Royal Canin® Urinary SO, Purina® ProPlan® Veterinary Diet UR Ox™/St™, Hill's Prescription Diet® w/d® Multi-Benefit, or Rayne Clinical Nutrition Adult Health-RSS™. Table food may be a problem for these dogs.
• Calcium phosphate stones. Dissolution has not proven to be effective. Prevention is complicated because these stones are uncommon and may result from several different underlying causes at once. Nutritional prevention of recurrence involves feeding wet versus dry food, limiting sodium intake, and managing urine pH (depending on the dog's metabolic profile). There are no specific diet recommendations. The dog may also need additional medication.
• Cystine stones. Dissolution may be possible using a protein-restricted therapeutic food with a controlled sodium level, and one that supports an alkaline urine pH (examples include Hill's Prescription Diet® u/d® or Royal Canin® UC Low Purine). Any existing urinary tract infection must be resolved. This is also the nutrient profile that would be used following surgery. Potassium citrate (brand names NutriVed, Urocit-K®) can be used to alkalinize the urine. Tiopronin (brand name Thiola®) may be used to bind to the excess cystine and remove it from the body.
• Struvite stones. Dissolution may by possible by resolving an existing urinary tract infection and utilizing an appropriate nutrient profile. The appropriate nutrient profile for dissolution is relatively high in fat, potentially providing worry about pancreatitis, which means close monitoring is necessary. The food will also cause increased thirst and more dilute urine. Diets include Hills Prescription Diet® s/d® or c/d®, Royal Canin Urinary SO™, Purina® Pro Plan® Veterinary UR Urinary™, and Rayne Clinical Nutrition Adult Health-RSS™. The complete prevention plan will depend on the individual dog, but will generally focus on creating a slightly acidic urine while monitoring to prevent formation of calcium oxalate crystals and/or stones, which can form in urine that is very acidic.
• Silica stones. These bladder stones are very rare. Dissolution has not yet been documented. Post-surgery, there is limited data to provide a clear path to prevention. General guidelines include feeding a nutrient profile with reduced vegetable protein and other plant-based ingredients, higher animal protein, feeding moist food versus dry, and feeding a food that supports an alkaline urine pH. A urine alkalinizing agent (such as the potassium citrate) may also be needed.

Regardless of the ultimate treatment of canine bladder stones - surgical removal or dissolution - nutrition will play a critical role in preventing recurrence. Once a nutritional profile has been chosen, it is important to feed only what has been prescribed, so speak to your veterinarian before offering any additional food or treats. The add-ons may undermine what the prescribed nutrient profile is able to do to prevent bladder stones from recurring.