What are bladder stones?
Bladder stones (also called 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. Many times, there is a mixture of both large and small stones present. All stones form because of disease or inflammation in the bladder.
What are the clinical signs of bladder stones?
The most common signs of bladder stones in cats are:
- blood in the urine (called hematuria) and
- straining to urinate (called dysuria).
Bleeding occurs because the stones rub against the bladder wall, irritating and damaging the tissues. Straining happens due to inflammation and swelling of the bladder walls or the urethra (the tube that connects the bladder to the outside of the body). Straining may also be caused by muscle spasms.
Large stones may act like a valve, causing a temporary 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 narrow urethra, where they become lodged and cause a complete obstruction. This problem occurs more frequently in male cats because their urethra is much longer and narrower.
"A complete obstruction is life-threatening and requires immediate emergency treatment."
If an obstruction occurs, the bladder cannot be emptied fully. This condition is an emergency, and is very painful, especially when pressure is applied to the abdomen. If the obstruction is not relieved, the bladder may rupture. A complete obstruction is life-threatening and requires immediate emergency treatment.
How did my cat get bladder stones?
Certain minerals are naturally found in your cat’s body. When these minerals are not properly processed by the cat’s urinary system, or when these minerals are found at higher-than-normal levels in the urine, they can crystallize. 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.
Several factors can influence this process. Urine pH (level of acidity), the presence of certain proteins in the urine, and the urine’s water content all affect stone formation. Diet can help change the pH of the urinary environment, predisposing them to crystal formation.
How quickly can bladder stones form?
Bladder stones can develop within a few weeks or may take months to form. The rate of urolith formation and growth varies, depending on factors such as diet, urine pH, and how much crystalline material is present in the urine.
How are bladder stones diagnosed?
Inflammatory diseases of the bladder are common in cats and produce the same signs as bladder stones. Therefore, veterinarians do not assume a cat has bladder stones based only on these clinical signs.
Some bladder stones can be palpated or felt with the fingers through the abdominal wall. However, failure to feel bladder stones does not rule them out because many are too small to be detected this way.
Most bladder stones are visible on X-rays or by an ultrasound exam of the bladder. These diagnostic imaging techniques should be performed on cats that show signs of abdominal pain or have repeated bouts of blood in the urine or straining.
Some types of bladder stones are radiolucent, meaning they cannot be seen on a normal X-ray, because their mineral makeup does not reflect X-ray beams. They can be detected by an ultrasound examination or with contrast X-rays, a specialized technique that uses dye or contrast material to outline the stones within the bladder.
How are bladder stones treated?
There are a few options for treatment. The fastest solution is to perform a cystotomy (surgery to open the bladder and remove the stones); however, it may not be the best option for patients that have other health concerns, or in whom general anesthesia could be risky. This routine surgery is a common choice and cats usually make a speedy postoperative recovery. Cats with a complete urethral obstruction caused by large stones require immediate surgical intervention.
In some cases, a cystotomy may not be necessary if the obstruction can be relieved by passing a catheter, especially if it is caused by soft plugs of crystals and mucus or urethral spasms.
Another option is to attempt to dissolve bladder stones with a special diet such as Hill's Prescription Diet C/D, Purina UR/StOX, or Royal Canin Urinary SO. This approach avoids surgery and can be a good choice for some cats; however, it has three disadvantages:
- It is not successful for all types of stones. Some stones do not respond to diet therapy.
- It is slow. It may take several weeks or a few months to dissolve a large stone, so the cat may continue to have bloody urine, straining, and repeated infections during that time. The risk of life-threatening urethral obstruction is still present while waiting for the stones to dissolve.
- Not all cats will eat the special diet. It must be consumed exclusively, or it will not work.
Voiding urohydropulsion is used less often and is potentially less successful due to the urethral diameter. If the bladder stones are very small, it may be possible to pass a catheter into the bladder to fill it and then flush the stones out by holding the patient upright and expressing their bladder. Sedation will likely be needed, but in some cases, the cat might need to be placed under general anesthesia. This may not work in some cases and would not be recommended in male cats.
If your veterinarian has a cystoscope (a very small camera on a long tube), it can sometimes be used to remove small stones from the bladder in females or males that have had a perineal urethrostomy performed. It is only an option for smaller stones and may not be recommended if there are many stones, due to the time required to retrieve the stones.
Are there any other treatment options?
Another option for bladder stone treatment is laser lithotripsy, which uses a cystoscope to guide a laser to contact the stone. The laser heats up the molecules around the stone, causing the stone to break into tiny particles that can then be flushed out of the bladder or retrieved with a small basket passed through the cystoscope. It allows for immediate removal of the offending stones without the need for surgery.
However, it has limitations that restrict its use, including time required to target multiple stones and the need for a large enough urethra to pass the cystoscope (i.e., it can’t be used in male cats or small females). Your veterinarian will discuss whether this is a good treatment option for your cat and if it is available in your area.
Can bladder stones be prevented?
Prevention is possible in many cases. There are at least four types of bladder stones in cats, each based on what they are made up of. If bladder stones are removed surgically or if small ones pass in the urine, they should be analyzed for their chemical composition. This allows your veterinarian to determine if a special diet or medication is appropriate. Regular checks of urine samples, or ultrasound examination of the bladder are helpful in all cases to detect early return of the problem and allow adjustments in diet or treatment.
