A cat looking up while standing on the floor next to a litter box.

Cancer Awareness: When It’s the Feline Bladder

Cats can have a proclivity to suddenly “going” outside of the litter box. Most of the time, it’s because of fairly innocuous reasons, like the cat doesn’t like the scent or texture of the litter. Or someone (who shall remain nameless) has failed to clean the box. Or worse, the cat is stressed by the bathroom remodeling project.

But sometimes, there can be something more serious involved, like urinary bladder cancer. Thankfully, this is a relatively rare occurrence for cats (it’s much more common in dogs), but it can be a reason for chronic urinary problems that just won’t improve.

Transitional cell carcinoma

The most common kind of bladder cancer in cats is called transitional cell carcinoma (TCC), which originates in the cells lining the bladder. This malignancy tends to occur in older, male cats, and like most cancers, it’s not clear what causes it.

It’s possible for cats to have other types of cancers or benign (non-cancerous) conditions that cause growths or thickening of the bladder wall, such as polyps or inflammatory masses. So it’s important to distinguish what, exactly, is behind the abnormal growth.

Signs of a potential problem

Cats with bladder cancer can show signs such as bloody urine, straining to urinate, frequent urination or difficulty urinating that may result in accidents outside of the litter box. If the tumor grows in a location that obstructs the urethra, or the tube in which urine flows from the bladder to the outside, the cat may be unable to urinate at all.

If these signs seem familiar, it’s because other urinary tract problems, such as infections, cystitis (inflammation of the urinary bladder) and urinary tract blockage have similar signs. Cats with bladder cancer can also develop secondary urinary tract infections, and treatment with antibiotics may not fully resolve the signs.

How bladder cancer is diagnosed

If your cat is showing signs of recurrent urinary tract infections that don’t resolve with treatment, your veterinarian may recommend additional diagnostic tests. With a urinalysis, a veterinary professional can examine urine sediment under a microscope. Among other things, they may see signs of bacteria, inflammatory cells, and in some cases, cancerous cells.

The doctor may then recommend abdominal X-rays or an ultrasound to examine the entire urinary tract, from the kidneys to the urethra, to look for evidence of a tumor or other problem. It’s usually more common to find problems such as stones in the bladder, but occasionally, an abnormal growth may be seen.

With other types of cancer, the veterinarian typically wants to obtain a sample of the cells, either through a fine needle aspirate, surgical biopsy or urinary catheterization. But sampling TCC cells can be problematic because in the process, tumor cells can “seed” themselves in other parts of the body. In some cases, cystoscopy, or the placement of a tube with camera into the urethra, can be used to obtain a tissue sample.

Once a diagnosis is made, the veterinarian may want to stage the cancer, or determine if it has spread to other locations. The use of X-rays and ultrasound may help determine if other parts of the body are involved, such as the lungs.

Types of treatment

When it comes to bladder cancer, cats may be slightly luckier than dogs. In dogs, the tumors tend to grow in the area where the bladder meets the urethra, which makes them almost impossible to remove surgically. In cats, the tumors tend to grow in other areas of the bladder. If the cancer is caught early, and the tumor is small, the surgeon may be able to remove it, but tumor recurrence can be common.

Radiation therapy can help the cat feel better but may not be curative. Other types of cancer, such as lymphoma, may be found in the bladder, and chemotherapy may be an option. Thankfully, bladder cancer is still relatively uncommon in cats.



The information in this blog has been developed with our veterinarian and is designed to help educate pet parents. If you have questions or concerns about your pet's health or nutrition, please talk with your veterinarian.


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