Urinary Bladder Cancer in Dogs

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Overview of Canine Urinary Bladder Cancer

The most common bladder tumor in dogs is a malignant tumor called transitional cell carcinoma. This cancer usually arises from the inside surface of the urinary bladder or urethra and less commonly from the muscular wall of the urinary tract. Transitional cell carcinoma accounts for 0.5 percent of all cancers in dogs.

The cause of transitional cell carcinoma is unknown, but carcinogens, or cancer causing chemicals, that are excreted in the urine may cause the cells that line the bladder and urethra to become cancerous. Exposure to insecticide dips applied to kill fleas and ticks may increase the risk of developing this type of cancer. Similarly, exposure to sprays used to control mosquitoes in marshy or wetland areas also may increase risk.

Cyclophosphamide, a drug used to treat cancer and certain immune diseases, is metabolized to a carcinogenic chemical called acrolein, which is excreted in the urine. Exposure to cyclophosphamide may increase a pet’s risk for development of urinary bladder cancer.

Breeds predisposed or reported to be at a higher risk for bladder cancer include Shetland sheepdogs, Scottish terriers, West Highland white terriers, beagles and wirehaired fox terriers.

Female dogs are affected more commonly than males. Neutered dogs are at a higher risk than are intact dogs. Obesity also may predispose to development of this type of cancer.

Urinary bladder cancer is life-threatening. Left untreated, it can result in obstruction of the urinary tract and inability to urinate. This form of cancer can also metastasize, or spread to other parts of the body. At the time of diagnosis, transitional cell carcinoma is estimated to have spread in more than 50 percent of dogs in which it is diagnosed. Survival of dogs with this type of cancer is dependent on the location of the tumor in the bladder, extent of disease and whether it has metastasized, and what treatments are prescribed. Survival time can range from weeks to more than a year.

What to Watch For

Signs of urinary bladder cancer in dogs may include: 

  • Blood in the urine
  • Straining to urinate
  • Increased frequency of urination with passage of small amounts of urine
  • Straining while defecating
  • Signs of exercise intolerance
  • Difficulty breathing or coughing

    In many cases, these signs can be present for many months before diagnosis. If your pet is showing any of these signs and does not seem to be getting better with treatment, additional tests should be done to rule out cancer as the cause.

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    Diagnosis of Urinary Bladder Cancer in Dogs

    Diagnostic tests are needed to recognize urinary bladder cancer and exclude other diseases. Tests may include:

  • Complete medical history and physical examination including rectal examination to palpate the urethra, bladder neck, male prostate gland and local lymph nodes
  • Plain X-rays of the abdomen to evaluate for masses and lymph node enlargement and of the chest to evaluate for metastasis
  • Complete blood cell count
  • Serum biochemistry tests to evaluate your pet’s general health, other body systems, and to identify metabolic consequences of urinary obstruction
  • Urinalysis to evaluate for white cells, red cells, bacteria or tumor cells
  • Cytology examination of urine to evaluate for tumor cells
  • Abdominal ultrasound examination to evaluate the location and extent of the bladder tumor, the status of regional lymph nodes, and the presence of obstruction of the urinary tract
  • Contrast dye X-ray studies to evaluate the location and extent of the bladder tumor in the place of abdominal ultrasound examination
  • Urethrocystoscopy by passing a rigid or flexible scope into the urethra and bladder under anesthesia to identify the location and extent of the tumor. This procedure allows for biopsy of the tumor, but usually requires referral to a veterinary specialist.
  • A relatively new test called V-TBA has become available to screen for the presence of a bladder tumor marker in the urine of dogs suspected to have transitional cell carcinoma.
  • Treatment of Urinary Bladder Cancer in Dogs

    Your veterinarian may refer you to a veterinary cancer specialist (oncologist) to discuss treatment options. Treatment for urinary bladder cancer may include one or more of the following:

  • Surgery for small masses confined to certain locations in the body of the urinary bladder. Unfortunately, many transitional cell carcinomas are found in parts of the bladder that are not amenable to surgery.
  • Cancer chemotherapy for some dogs with transitional cell carcinoma
  • The non-steroidal anti-inflammatory drug piroxicam (Feldene®) has show some promise in symptomatic treatment of some dogs with transitional cell carcinoma. In one study, tumors regressed in approximately 25 percent of treated dogs, remained stable and did not grow in 50 percent of treated dogs, and progressed in 25 percent of treated dogs.
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