Bladder Cancer: Clinical Signs, Diagnosis and Treatment

Urinary System

The urinary system consists of the kidneys, the ureters, the urinary bladder and the urethra. The kidneys are the organs that filter the blood to remove waste and maintain the electrolyte balance of the body. The filtered waste becomes urine, travels to the urinary bladder via the ureters, and continuously collects in the bladder.

The bladder is able to expand due to the special properties of its wall and inner lining. When an animal urinates, the urine is voided from the body through the urethra.

Graphic showing a dog's urinary tract

What Is Bladder Cancer?

The most common type of urinary bladder cancer is transitional cell carcinoma (TCC). This is a tumor of the cells that line the inside of the urinary bladder. Other less common types of tumors of the bladder may include leiomyosarcomas, fibrosarcomas and other soft tissue tumors. TCC can also appear in the kidney, ureters, urethra, prostate or vagina. It can spread (metastasize) to the lungs, lymph nodes, bones or other organs.

Approximately 20% of dogs with bladder cancer have metastases at the time of diagnosis. Bladder cancer is much more common in dogs than cats, but TCC only accounts for less than 1% of all reported cancers in dogs. TCC can occur in any breed but is most common in Shetland sheepdogs, Scottish terriers, wirehair fox terriers, West Highland terriers, and beagles. Middle-aged or elderly female dogs are most commonly affected. Some studies have suggested that chronic exposure to certain chemicals (petrochemicals, pesticides) may increase the risk for a dog to develop bladder cancer.

Clinical Signs

The signs of bladder cancer can be similar to those seen with urinary tract infections. These include small, frequent urination, painful urination, bloody urine and incontinence. Symptoms will often improve initially with administration of antibiotics (as bladder infection is a common concurrent disease) but then recur a short time later.

A veterinarian may feel the tumor during abdominal palpation if it is large. If the tumor has spread to lymph nodes within the abdomen, they may be palpated during a digital rectal examination. The spread of tumor to bones can cause lameness or bone pain.

If the bladder tumor invades into the urethra, it can block urine flow and cause straining to urinate. If severe enough, this can eventually lead to kidney damage (hydronephrosis) and possibly kidney failure. Complete inability to urinate is a medical emergency and should be addressed by a veterinarian immediately.

Diagnosis

Treatment

Prognosis

The long-term prognosis for pets with bladder cancer is generally poor, regardless of treatment. However, with treatment, pets can have an improved quality of life for a period of time. On average, dogs with TCC of the bladder live 4-6 months without treatment, and 6-12 months with treatment.

For more information on this subject, please talk to the veterinarian treating your pet.