Bladder Stones in Dogs



What are bladder stones?

Bladder stones (uroliths or cystic calculi) are rock-like formations of minerals that develop in the urinary bladder.
There may be a large, single stone or a collection of stones that range in size from sand-like grains to gravel. It is
common for a mixture of both small and large stones to be present.


What other kinds of stones are there?

Gall stones form in the gall bladder and contain bile salts. Kidney stones are mineralized formations that develop in
the kidney. Neither of these are directly related to bladder stones. Even though the kidneys and urinary bladder are
both part of the urinary system, the development of kidney stones is not usually linked to the development of bladder
stones. All stones form as a result of disease or inflammation in the affected structure.



What are the clinical signs of bladder stones?

The most common signs that a dog has bladder stones are hematuria (blood in the urine) and dysuria (straining to
urinate). Hematuria occurs because the stones rub against the bladder wall, irritating and damaging the tissue and
causing bleeding. Dysuria may result from inflammation and swelling of the bladder walls or the urethra, from muscle
spasms, or due to a physical obstruction to urine flow caused by the presence of the stones. Veterinarians assume
that the condition is painful, because people with bladder stones experience pain, and because many clients remark
about how much better and more active their dog becomes following surgical removal of bladder stones.

Large stones may act almost like a valve or stopcock, causing an intermittent or partial obstruction at the neck of the
bladder, the point where the bladder attaches to the urethra. Small stones may flow with the urine into the urethra
where they can become lodged and cause an obstruction. If an obstruction occurs, the bladder cannot be emptied
fully; if the obstruction is complete, the dog will not be able to urinate at all. If the obstruction is not relieved, the
bladder may rupture.  A complete obstruction is potentially life threatening and requires immediate emergency
treatment. A urinary obstruction will usually be recognized in a dog that is straining to urinate without producing any
urine, or is only producing small squirts of urine.



How did my dog get bladder stones?

There are several theories of how bladder stones form. The most commonly accepted theory is called the
Precipitation-Crystallization Theory. This theory states that one or more stone-forming crystalline compounds is
present in elevated levels in the urine. This may be due to dietary factors or due to some previous disease in the
bladder, especially a bacterial infection. Sometimes the condition may be due to a problem with the body's
metabolism. When the amount of this compound exceeds a threshold level, the urine becomes saturated and cannot
hold any more of the compound. The saturation level depends on the specific minerals that are present and the pH of
the urine. The excess precipitates out of solution and forms tiny crystals. The sharp crystals irritate the bladder lining,
causing a production of mucus. The crystals and mucus stick together, forming clusters that gradually enlarge and
harden into stones.  This is similar to the way "rock candy" is formed.



How quickly can bladder stones form?

Bladder stones can develop within a few weeks or they may take months to form. Speed of growth will usually depend
on the quantity of crystalline material present and the degree of infection present. Although it may take months for a
large stone to grow, some sizeable stones have been documented to form in as little as two weeks.



How are bladder stones diagnosed?


The symptoms of bladder stones are similar to those of an uncomplicated bladder infection or cystitis. Most dogs that
have a bladder infection do not have bladder stones.  Therefore, we do not conclude that a dog has bladder stones
based only on these common clinical signs.

Some bladder stones can be palpated (felt with the fingers) through the abdominal wall. However, failure to palpate
them does not rule them out. Some stones are too small to be felt in this manner, or the bladder may be too inflamed
and painful to allow palpation.

Most bladder stones are visible on radiographs (x-rays) or an ultrasonic bladder examination.  Some bladder stones
are radiolucent, or are not visible on radiographs because their mineral composition does not reflect x-ray beams.
They can be detected by an ultrasound examination or with a radiographic contrast study, a special x-ray technique
that uses dye or contrast material to outline the stones within the bladder. Therefore, one or more of these diagnostic
imaging techniques should be performed on dogs that show signs of abdominal pain or have recurrent episodes of
cystitis.



How are bladder stones treated?

In general, there are three main treatment options for bladder stones: 1) surgical removal; 2) non-surgical removal by
urohydropropulsion, and 3) dietary dissolution. The specific treatment that is recommended for your dog will depend
on the type of stone that is present. Your veterinarian will discuss the pros and cons of each treatment option with
you in more detail, based on your dog's individual circumstances.

Option 1: Surgical removal of bladder stones. This is often the quickest way of treating bladder stones; however, it
may not be the best option for patients that have other health concerns, or in whom general anesthesia could be
risky. With this option, the stones are removed via a cystotomy, which means that the bladder is surgically exposed
and opened so that the stones can be removed. This surgery is routinely performed by many veterinarians and dogs
usually make a rapid post-operative recovery. If the stones have obstructed the urethra, so that the dog is unable to
urinate, an emergency procedure must be performed IMMEDIATELY to save the dog's life.

Option 2: Non-surgical removal. If the bladder stones are very small it may be possible to pass a special catheter into
the bladder and then flush the stones out, using a technique called urohydropropulsion. In some cases, this
procedure may be performed with the dog under heavy sedation, although general anesthesia is often necessary. If
your veterinarian has a cystoscope, small stones in the bladder can sometimes be removed with this instrument, thus
avoiding the need to cut the abdomen and bladder open. Either of these procedures may be used to obtain a sample
stone for analysis so that your veterinarian can determine if dietary dissolution is feasible.

Option 3: Dietary dissolution. In some cases, bladder stones can be dissolved by feeding the dog a special diet that is
formulated to dissolve bladder stone(s). This diet will be tailored to the specific type of stone that is present. The
advantage of this option is that it avoids surgery. It can be a very good choice for some dogs. However, it has three
disadvantages:

•It is not successful for all types of stones. Stone analysis is necessary to determine if it is the type of stone that can
be successfully dissolved. This may not be possible in all cases. Sometimes, your veterinarian will make an educated
guess on the type of stone, based on the radiographic appearance and the results of a urinalysis.

•It is slow. It may take several weeks or a few months to dissolve a large stone so the dog may continue to have
hematuria, dysuria, and recurrent infections during that time. The risk of urethral obstruction remains high during this
period.

•Not all dogs will eat the special diet. These diets will not work unless they are fed exclusively. This means that NO
TREATS or supplements can be given to your dog while it is on the special diet.


Are there any other treatment options?

In some selected referral centers, a fourth option may be available to treat bladder stones. This option is ultrasonic
dissolution, a technique in which high frequency ultrasound waves are used to disrupt or break the stones into tiny
particles that can then be flushed out of the bladder.  It has the advantage of immediate removal of the offending
stones without the need for surgery.  Your veterinarian will discuss this treatment option with you if it is available in
your area.


Can bladder stones be prevented?

Prevention is possible in some cases, depending on the chemical composition of the stones.  There are at least four
types of bladder stones common in dogs (see our handouts on struvite, urate, cystine and calcium oxalate bladder
stones for more specific and detailed information).

Whenever possible, bladder stones (either those that are removed surgically or those small ones that have been
passed in the urine), should be analyzed for their chemical composition. This will permit your veterinarian to
determine if a special diet will be helpful in preventing recurrence. If the stones formed because of a bacterial
infection, it is recommended that periodic urinalyses and urine cultures be performed to detect sub-clinical
recurrences and determine if antibiotics should be prescribed. Periodic bladder x-rays or ultrasounds may be helpful
in some cases to determine if bladder stones are recurring.

Early recognition may allow your veterinarian to adjust your dog's diet or medications before your pet requires
surgery.