and Susan E. Aiello, DVM, ELS
Cancers of the bladder and related structures (e.g., the urethra) are relatively uncommon in dogs and very uncommon in cats.
The most common type of cancer is known as transitional cell carcinoma, which is a locally invasive tumor usually found at the neck of the bladder where it feeds into the urethra. This cancer typically occurs in older dogs, most often in Beagles, Scotties, Airedales, Shetland Sheepdogs, and Collies.
The most common signs of urinary tract cancer are recurrent urinary tract infections, straining to urinate, frequent urination of small amounts, and blood in the urine.
In some cases, the cancer can block the outflow of urine, leading to persistent straining but little to no urine flow.
Diagnosis begins with a thorough physical examination. It is often difficult to feel these tumors by abdominal palpation, but rectal or vaginal (when applicable) examination may reveal a thickened area at the neck of the bladder. Urinalysis may reveal blood in the absence of infection, or the presence of cancerous cells. Bladder cancer usually does not show up on plain x-rays, so your veterinarian may recommend contrast radiography. In this procedure, dye and/or air are injected into the bladder (through a catheter) to outline the bladder wall. The wall of the bladder can also be visualized using ultrasound. Other tests may include blood work to check overall health, and chest x-rays to look for metastases, which develop in about one-third of affected dogs.
Surgical removal of the tumor is the treatment of choice, but this is often difficult without causing damage to the muscles and nerves that control urination, leading to permanent incontinence.
In some cases, radiation and/or chemotherapy can be used to control tumor growth and keep your pet comfortable. Unfortunately, the overall prognosis for pets with transitional cell carcinoma is guarded to poor, especially if the cancer has already metastasized to lymph nodes or other organs.
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