Urinary stones, or uroliths, can be incredibly painful for a dog or cat. These stones -- formed by deposits of mineral salts -- can appear anywhere along your pet’s urinary tract and cause irritation as well as obstruction. Some urinary stones may dissolve with the help of supplements, medications, or dietary changes, but others will require surgical removal.
Here we will review the causes, symptoms, and treatment of urinary stones in dogs and cats.
Causes of Urinary Stones in Dogs and Cats
Urinary stones are formed from urine crystals composed of mineral salts. There are different types of urinary stones, including calcium oxalate, cystine, struvite, calcium phosphate, silicate, and urate.
Many factors can contribute to the formation of stones, but the most common is a high concentration of crystals in the urine. The high concentration can result from changes in the urine’s pH which lead to crystal formation, increased crystal secretion by the kidneys, and increased reabsorption of water by the kidneys. Genetics, diet, medications, frequency of urination, and urinary tract infections can also contribute to stone formation.
Any pet can develop urinary stones, but some breeds are predisposed to certain types.
Struvite stones are the most common type in any dog or cat, and they form from ammonia magnesium and phosphorus in the urine. They are commonly associated with urinary tract infections. The most commonly affected breeds include:
Calcium oxalate stones are about as common as struvite stones and are thought to be associated with a genetic predisposition. The most commonly affected breeds include:
Cystine stones, which may form as a result of a defect that produces excessive amounts of the amino acid cystine, are most common in the following breeds:
Silicate stones may be related to dietary intake of silica acid, silicates, and magnesium silicate, which can be found in soybeans, corn gluten, and other ingredients. Commonly affected breeds include:
Urate stones often occur in animals who have trouble metabolizing uric acid in the liver.
The Dalmatian is the breed most affected by this type of stone.
Symptoms of Urinary Stones in Dogs and Cats
The symptoms exhibited by your pet will depend on the location of the stones in the urinary tract. Most pets have stones in the bladder or urethra, and a small percentage may have stones in the kidney or ureters. Regardless of the location, all urinary stones can damage the lining of the urinary tract and cause irritation, often resulting in a urinary tract infection.
Symptoms of stones in the bladder may include:
- Straining to urinate
- Urinating small amounts often
- Blood in the urine
- Urine accidents
- Abdominal pain
Symptoms of stones in the urethra may include:
- Attempting to urine with nothing coming out
- Dribbling urine
Stones in the urethra can cause an obstruction and block up the urinary flow. This can cause serious problems for your pet, including kidney failure. If you notice that your pet is unable to urinate, you should seek veterinary attention immediately.
Symptoms of stones in the ureters (the tubes that carry urine from the kidneys to the bladder) may include:
Stones in the ureters can also cause obstruction and severe kidney damage.
Treatment for Urinary Stones in Dogs and Cats
Urinary stones can only be definitively diagnosed once they are removed from the pet and analyzed. However, your veterinarian may perform certain tests beforehand to search for stones in the urinary tract and evaluate the urine. These tests may include x-rays, ultrasounds, contrast urography (which can reveal the structure of the urinary tract), urine culture, and urinalysis.
Treatment for urinary stones will depend on the size, location, and nature of the stones.
- Surgery will almost always be necessary if the stones are causing an obstruction or are likely to do so. Most stones are removed with a cystotomy, a procedure in which the bladder is opened. Stones located in the urethra are often flushed into the bladder so that they can be removed there. In some pets this may not be possible, and a urethrostomy -- a procedure in which the urethra is opened -- will be required.
- Some urinary stones can be resolved without the need for surgery. Supplements, diet changes, and increased water intake can all help to dissolve urinary stones. Urinary stone medications such as Ursodiol may also be recommended to dissolve certain types of stones. Increased water intake -- either through more drinking or through wet food -- helps to dilute the urine. Low protein diets help to reduce the production of certain minerals that tend to form stones.
- Antibiotics may be prescribed if there is a bacterial infection.
Diets for Dog and Cat Urinary Stones
Urinary stones are formed by deposits of minerals within your cat or dog’s bladder and can cause your pet to experience trouble with urination and irritate the bladder lining. Some of the common tip-offs that your pet is struggling with urinary stones are a very frequent need to urinate, difficulty urinating, and licking of the genitals.
Depending on which type of stone your pet has been diagnosed with, find out which type of diet can help to treat and prevent the urinary stones.
Hydration:
With pets that suffer from urinary stones, it is particularly important to always have water available -- dehydration can lead to the a more concentrated urine, and in some dogs or cats this can lead to urinary crystals and stone formation. Allowing pets access to lots of fresh water during and after treatment is helpful. In many cases, vets will recommend a switch from dry food to wet food - or at least to a mix of wet and dry food -- since wet food contains more liquid, and can help keep your pet hydrated. This can be especially helpful for cats.
Tips: Putting a small amount of low sodium broth in your dog’s water bowl can encourage drinking. For cats, ice cubes in the water, chicken broth, or small amounts of tuna juice can make it more appealing.
Treating and Preventing Stones With Diet:
Before trying out a preventative diet for your pet, it is important to know what kind of stones your cat or dog forms. Some types of stones can be treated with Ursodiol and other meds while others need a different treatment option. Here are the main types of stones, and the diets associated with them for treatment and prevention:
1. Calcium Oxalate:
These stones are common in both dogs and cats. In dogs, they’re thought to be associated with a genetic predisposition, mostly in small dogs, who do not drink enough water. Dietary trends in cat foods in the 1990’s and early 2000’s to prevent struvite crystals may have actually led to an increase in calcium oxalate.
Unfortunately these stones do not dissolve and surgical removal is often necessary. To prevent these stones from forming, feed pets a diet with lower calcium and oxalate, such as Royal Canin Urinary SO or Purina NF Kidney Function, or IAMs Urinary O-moderate ph/O for cats.
More importantly, watch what snacks and table foods you feed on the side, since some foods like vegetables tend to be high in oxalate.
2. Struvite:
These are stones that form from ammonia magnesium and phosphorus in the urine.They’re the most common variety of stones to form in cats and are often associated with urinary tract infections in dogs. They can be treated with a special diet, such as Hills s/d or Urinary SO, which work by dissolving the stones.
Once your vet confirms that these stones have dissolved, your dog or cat then needs to be on a maintenance diet for the prevention. Common choices are Hill's c/d, Royal Canin Urinary SO, and IAMs Urinary S-Plus low pH/S for cats. Preventative diets work by making sure the urine acidity is approximately 6.5 pH. In addition, these diets tend to be lower in protein (which reduces ammonia production) phosphorous, and magnesium.
If your dog has struvite stones due to a urinary tract infection, then antibiotic and diet therapy will resolve the problem in many cases, and once the stones have been resolved your dog does not necessarily need a special diet. Your veterinarian will be able to help you make these decisions.
3. Urate:
Urate stones can occur because of a genetic conditions or due to portosystemic shunts, a medical condition. This stone is relatively rare in pets. Dogs that are prone to forming urate stones -- like Dalmatians -- might do well to have a moderate to low protein diet. More importantly, the sources of protein should be low in purines, which form urate. Protein sources such as dairy, egg, and soy are preferred. Some possible foods that your vet may recommend are Hill’s u/d or Royal Canin UC Low Purine.
4. Cystine:
The causes of this particular stone are not known, but might relate to genetics, particularly for Mastiffs and Bulldogs. For dogs that have formed cystine stones, a diet that promotes an alkaline urine can be prescribed preventatively. However, diet cannot be used as a treatment method. Surgical removal or certain drugs can be used to get rid of the stones. Currently, diets such as Hill’s u/d or Royal Canin UC Low Purine are used to help manage this disease.
Frequently Asked Questions
What causes bladder stones in dogs and cats?
Bladder stones, also known as cystic calculi or urinary stones, can form in the urinary bladder of both dogs and cats due to various factors. These stones can be of different types, including calcium oxalate stones and struvite stones, each with its own chemical composition and formation process. Calcium oxalate stones form when there's an excess of calcium in the urine, which combines with oxalate to form crystals. Over time, these crystals accumulate and solidify into stones. Factors contributing to calcium oxalate stone formation can include diet, genetics, and certain medical conditions. Dr. Alex Gallagher, a clinical assistant professor at the College of Veterinary Medicine, University of Florida in Gainesville, says that 50% of dogs with calcium oxalate stones will face a recurrence within 2 years.
Struvite stones are composed of magnesium ammonium phosphate. They often develop in animals with urinary tract infections caused by urease-producing bacteria. These bacteria produce urease, an enzyme that increases the urine pH, leading to the formation of struvite crystals. These crystals can then aggregate and form stones. Bacterial urinary tract infections (UTIs) can contribute to stone formation, particularly in the case of struvite stones. When bacteria infect the urinary tract, they can alter the chemical composition of the urine, promoting the formation of crystals that eventually develop into stones.
The mineral composition of the urine plays a significant role in stone formation. Changes in pH and minerals like calcium, oxalate, magnesium, and phosphate can influence the precipitation of crystals, which may eventually form stones.
Conditions like Lower Urinary Tract Disease (LUTD) can predispose animals to bladder stone formation. This can include anatomical abnormalities, inflammation, or other factors that affect urinary flow or the composition of urine. Bladder stones can cause urinary obstruction, particularly if they are large or numerous. Obstruction can lead to serious complications such as kidney damage or rupture of the bladder wall.
How to tell if a dog has bladder stones?
Bladder stones in dogs can manifest through a variety of clinical signs. Dr. Jennifer Coates, DVM, says that common signs include urinary accidents indoors, straining to urinate, and changes in urine flow or concentration. If your affected dog experiences any of these symptoms, especially alongside abdominal discomfort, it warrants immediate veterinary attention.
Small bladder stones might not always cause obvious symptoms but can still lead to serious issues, including complete obstruction of urine flow. This obstruction can be potentially life-threatening, causing significant pain and distress to your dog. Emergency treatment may involve removing the obstruction immediately. If the stones are small, your veterinarian may attempt to dissolve them with a special diet. However, if the stones are large or causing a complete obstruction, surgical intervention may be necessary.
Diagnosis usually involves imaging techniques like X-rays or ultrasound examinations to visualize the stones and evaluate the condition of the bladder wall. In severe cases, a urinary catheter may be inserted to relieve the obstruction and alleviate your dog's discomfort. Prompt recognition and treatment of bladder stones are crucial to prevent complications such as urethral obstruction, which can lead to serious health issues. If you notice any signs of urinary distress or abdominal discomfort in your dog, seek veterinary care immediately.
What food causes bladder stones in dogs?
Bladder stones in dogs can be caused by various factors, including their diet. One common culprit is high levels of certain minerals like calcium, phosphorus, and magnesium in the dog's diet. When these minerals are present in excessive amounts, they can crystallize and form stones in the bladder. Foods that are high in these minerals, such as some commercial dog foods or homemade diets lacking proper balance, can contribute to the formation of bladder stones in dogs. Additionally, diets with excessive protein levels may also increase the risk of bladder stone formation in some dogs. While organ meats like liver, kidney, and heart are nutritious and provide essential vitamins and minerals, they are also high in certain minerals like phosphorus. Some fish, particularly those with small bones, can be high in minerals like calcium and phosphorus. Leafy greens like spinach and beet greens are rich in nutrients, but they also contain oxalates, which can contribute to the formation of certain types of bladder stones, such as calcium oxalate stones, when consumed in large quantities. Bone broth made from bones rich in minerals like calcium can contribute to mineral imbalances if fed in excess.
What medication dissolves bladder stones in dogs?
In dogs, bladder stones, particularly struvite stones, can be managed with a combination of medication, dietary therapy, and sometimes surgical intervention. When it comes to medication, antibiotics play a crucial role, especially if there's an associated urinary tract infection (UTI). Antibiotics help to clear the infection, which is often a contributing factor to the formation of struvite stones.
For dissolving struvite stones specifically, therapeutic diets are highly recommended. Dr. Aly Cohen suggests brands like Hill’s Prescription Diet c/d, Royal Canin Urinary SO, and Purina Pro Plan UR are formulated to promote urinary health and help dissolve struvite stones. Dietary therapy usually works by altering the pH of the urine and reducing the mineral content, making it less conducive to stone formation.
In addition to antibiotics, certain medications may be prescribed to help dissolve bladder stones in dogs, particularly struvite stones. Potassium citrate helps to alkalinize the urine, making it less favorable for the formation of struvite crystals. D-mannose supplements can help prevent bacteria from adhering to the walls of the urinary tract, reducing the risk of UTIs, which can contribute to stone formation.
Uroeze (Ursodiol) helps to dissolve certain types of bladder stones by altering the composition of bile acids in the liver, which in turn affects the formation of stones in the urinary tract.
NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) may be prescribed to manage pain and inflammation associated with bladder stones. Alpha-adrenergic blockers can be used to help relax the muscles of the urethra, making it easier for small stones to pass.
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