Lining the urinary bladder are cells called transitional cells that protect the body from the urine inside the bladder even as the bladder stretches to accommodate larger volumes of urine. Transitional Cell Carcinoma (TCC) is a malignant tumour that develops from the transitional cell lining of the bladder.
Bladder cancer is not as common as other forms of cancer in dogs but more than half of all bladder tumours that develop are TCCs. Some breeds are predisposed to this type of cancer including Shetland Sheepdogs, West Highland White Terriers, Beagles and Scottish Terriers.
Unlike bladder cancer in humans, dogs usually develop the more invasive form of bladder cancer that grows quickly and spreads to the lymph nodes or other organs in the body such as the liver or lungs. And as with most pet cancers, TCC most often affects older dogs.
TCC usually appears in the lower neck of the bladder and causes partial or complete obstruction to the flow of urine outside the body making it difficult or impossible for affected dogs to relieve themselves. Unfortunately, this location also makes it unlikely, in most cases, to surgically remove the tumour.
The exact cause of TCC is not known. Genetics likely plays a role as several breeds have a much higher risk of developing TCC than other dogs. Environmental factors such as exposure to lawn pesticides or herbicides and insecticides found in some flea control products are linked to the development of TCC. Also, the chemotherapy drug cyclophosphamide is known to cause TCC.
A link between second-hand smoke and the development of TCC in dogs may warrant further study as smoking is the greatest cause of TCC in humans. Female dogs have a tendency to develop TCC more than males and some vets speculate this is because females don’t mark their territory like males do hence storing urinary toxins longer.
A tissue biopsy is the best way to diagnose TCC as other conditions such as bladder infections and bladder stones have similar symptoms. Some routine tests such as urinalysis and cultures will rule out a bladder infection and x-rays will help rule out bladder stones. Because of the location of the bladder, vets will have to obtain the tissue biopsy through surgery, urinary catheter or cystoscopy, which means inserting a fibreoptic scope into the bladder.
Chest x-rays and ultrasound of the abdomen are used to determine whether or not the cancer has spread to the lungs, lymph nodes or other organs. If a mass is discovered in the neck of the bladder, this is often enough to make a TCC diagnosis.
Most dogs with TCC have the highly malignant form located in the neck of the bladder, which makes surgery impossible. (The only way TCC is operable is if the tumour is small when diagnosed and located away from the neck of the bladder.) As a result, chemotherapy is the treatment of choice for most dogs with TCC. The type of chemo drugs used will depend on the size of the tumour, the stage of the disease and how far it has spread.
Radiation therapy may be used to control TCC growth in the bladder but has many adverse effects including incontinence, inflammation of the urinary bladder and difficulty urinating.
Unfortunately, a TCC diagnosis is not good news — survival times for dogs where the cancer has spread to the local lymph nodes and/or other organs is only about two months, compared with eight months with no local lymph node involvement.
However, there are a few ways to make urinating more comfortable for dogs with TCC. A permanent urinary catheter can be implanted in the dog’s urinary tract but this comes with the increased risk of bladder infection. Also guardians will have to empty the drainage tube regularly and make sure they keep the catheter clean.
The other way is through a metal stent, which is placed in the urethra to allow urine to pass more easily. With this treatment incontinence is common and the dog will likely need to wear diapers indoors.
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