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 petโs 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 urineโs
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 dogโs 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 dogโs 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, theyโre
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 1990โs and early 2000โs 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.Theyโre 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 Hillโs 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 Hillโs u/d or Royal Canin UC Low Purine are used
to help manage this disease.
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