Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Bladder Stones: An Uncomfortable Problem

Pet Column for the week of December 10, 2001

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

Urinary tract infections are a very uncomfortable problem for humans and animals alike. In pets, especially cats, urinary tract infections can sometimes be accompanied by bladder stones, which can both initiate and promote infection in the bladder.

Dr. Christine Merle, a veterinarian formerly at the University of Illinois College of Veterinary Medicine in Urbana, says, "While dogs do get urinary tract infections, cats are much more susceptible." Female cats are also more susceptible than male cats. This may be because the urethra (opening from the bladder to the outside world) is very short in female cats, and it is close to the rectum, where there is a large amount of bacteria. In addition, cats do more grooming than dogs, which can spread bacteria.

Dogs are usually housebroken, and because they go outside, there is more opportunity for an owner to notice when there is a problem. The owner may notice straining or blood in the urine sooner. Infections often go unnoticed in cats because the owner may not see the cat using the litter box. Often, cat owners don't notice there is a problem until their pet stops using the box. Dr. Merle says, "While some cats stop using the litter box for behavioral reasons, it is important to rule out a medical problem before assuming that the cause is behavioral."

Since urinary tract infections can be caused by a multitude of factors, it is often difficult to discover the cause. The origin of an infection could be as simple as an overgrowth of bacteria or as complicated as bladder stones.

The formation of a bladder stone is very much like the formation of a pearl inside an oyster. It often forms from a single irritating particle called a nidus, which consists of a tiny particle such as small bacteria. Minerals are deposited on its surface, and over time it grows larger and can become very irritating to the lining of the bladder.

In female cats, these stones can cause recurrent infections with signs such as straining and blood in the urine. Infections caused by bladder stones often respond to antibiotics but return once the antibiotics are discontinued. In male cats, stones can cause infection and, if a bladder stone becomes lodged in the urethra, make the cat unable to urinate. Such an obstruction can result in the accumulation of urine in the bladder, which can cause the bladder to rupture, a medical emergency that is fatal if untreated.

If bladder stones are suspected, it is a good idea to take X-rays and do an ultrasound examination. Some stones can be seen on a regular X-ray, while others require ultrasound in order to see them. Ultrasound can also identify the presence of sandy residue and thickening of the bladder wall, both of which are signs of possible bladder stone formation.

Because there are several kinds of bladder stones, it is important to find out what kind of stone an animal has before starting treatment. Some stones can be dissolved with medication and others, such as calcium oxalate stones, cannot.

The only treatment for some stones is surgical removal. Surgically removed stones should be analyzed so a plan can be made to avoid the recurrence of stones in the future. Prevention may include a change in diet, medication, and prevention of bacterial infections that can lead to the formation of stones. Chronic problems with stones and bladder infections that do not respond to standard treatments may require a consultation with a surgeon or specialist.

If you have any questions regarding urinary tract infections or bladder stones, please contact your local veterinarian.