The most common form of bladder cancer in dogs is a Transitional Cell Carcinoma (TCC). It is a tumor made up of the epithelial cells that line the bladder wall. It commonly develops in the trigone area (the base of the bladder where the urethra originates), making surgical removal very difficult or impossible. As the cancer grows and invades a greater portion of the bladder wall, it may physically obstruct urine flow or cause the tissue to become less elastic. Straining to urinate, dysuria (pain), hematuria (bloody urine), and increased frequency of urination are the most common symptoms. Although tumors of the urinary tract are relatively uncommon in dogs, transitional cell carcinomas account for more than 75% of bladder related cancer.
As with many cancers, the specific cause of transitional cell carcinoma is speculative or unknown. Environmental carcinogens, as well as a genetic predisposition to bladder cancer, are likely factors. TCC is more likely to occur in female and obese dogs. The average age of dogs diagnosed with TCC is between 9 and 11 years. Any breed can be affected; however, Scottish terriers (Scotties), West Highland Terriers (Westies), Shetland sheepdogs (Shelties), Eskimo dogs, and Dachshunds appear to have breed predilections.
Many transitional cell tumors will exfoliate (shed cells easily) a large number of malignant cells in the urine. These may be visible under the microscope in the urine sediment, a part of the urinalysis. The presence of inflammation in the bladder can cause normal transitional cells to resemble malignant cells so it can be difficult to differentiate inflammation in the bladder from malignancy. There can be many other causes of symptoms that are similar to those of bladder cancer; therefore, conditions such as bladder and kidney stones, kidney disease, and urinary tract infections must be ruled out. Generally, a complete chemistry panel, blood count, abdominal x-ray, and urine culture are performed along with a urinalysis as a diagnostic workup for symptomatic dogs. To aid diagnosis, a contrast medium may be injected into the bladder that will help outline the bladder wall on an x-ray. Ultrasound can also be a useful diagnostic tool. An obvious mass in the trigone area of the bladder is very suspicious for transitional cell carcinoma.
Surgery to remove bladder cancer is seldom effective or even possible due to the invasiveness of this type of tumor. If the mass is consolidated and does not affect the sphincter muscle of the bladder or the ureters (the tubes that connect the kidneys to the bladder), surgery may be attempted. In a few cases, complete excision (surgical removal) may be curative. Transitional Cell Carcinomas tend to be fairly aggressive, spreading to regional lymph nodes and other organs in the body.
Chemotherapy (drug treatment for cancer) is recommended for dogs whether surgery is an option or not. Peroxicam is a non-steroidal anti-inflammatory drug (NSAID) that may be useful in slowing the progression of TCC tumors. The mechanism by which this medication acts on TCC is unclear. Since all NSAIDs can cause stomach ulceration, Peroxicam may be combined with antacids or misoprostol (Cytotec), a drug that protects the gastric mucosal lining, to avoid potential side effects. Misoprostol should not be handled by pregnant women. Mitoxantrone is another chemotherapy drug that is combined with Peroxicam. This combination is favored by many oncologists to improve survival times.
A consultation with an oncologist is always recommended for TCC patients. This type of cancer should be treated swiftly and aggressively in order to achieve the best quality of life for the greatest length of time.