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.
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