Bladder cancer is not very common in dogs – it accounts for approximately 2% of all cancers in dogs.
The bladder is shaped like an empty balloon, and it collects urine before the body releases it as waste.
The most common form of dog bladder cancer is a malignant cancer tumor called transitional cell carcinoma (“TCC”, aka urothelial carcinoma).
The tumor is developed from the cells lining the bladder (transitional epithelial cells). Therefore, such tumors are usually found in the inside lining of the bladder.
As the tumor grows, it takes over the space that is used for holding urine. As you can imagine, this obstructs the flow of urine from the kidneys to the outside of the body.
Canine transitional cell carcinoma is fairly aggressive. In one out of every 10 instances, it spreads to other sites of the body, such as the lungs, the bones, or the lymph nodes near the bladder.
Causes of Bladder Cancer in Dogs
As in other forms of cancer, the exact cause of this cancer is unknown, but many vets believe that several contributing factors can cause canine transitional cell carcinoma to develop in dogs.
Because this type of cancer is more common in specific breeds of dogs, we can assume that there is an element of genetic predisposition.
In particular, Scottish Terriers have a much higher risk of developing bladder cancer than other dogs.
Other breeds susceptible to this cancer include the Shetland Sheepdogs, the Beagles, West Highland White Terriers, and Wire Hair Fox Terriers.
For some reason, female dogs are twice as likely to get bladder cancer than males.
Neutered dogs are four times more likely to develop bladder cancer than intact males.
Exposure to Pesticides
Another risk factor is exposure to pesticides and herbicides, especially in yard spray. A study by Purdue University found that dogs exposed to herbicide-treated lawns were seven times more likely to develop TCC!
“Old generation” flea dips are also responsible for causing bladder cancer in dogs.
This chemotherapy drug can trigger bladder cancer in dogs. If your dog had a previous cancer of a different kind and was treated with cyclophosphamide, he may have a higher risk of developing bladder cancer later on in life.
Symptoms of Bladder Cancer in Dogs
In fact, one other sign of bladder cancer is repeated bladder infections.
So if your dog has repeated bladder infections, or is showing signs of a bladder infection, be sure to get a proper diagnosis to rule out the possibility of bladder cancer.
Since canine transitional cell carcinomas can spread rather rapidly, as the disease progresses, the dog will show other symptoms.
For example, if the tumor has spread to the bones, the dog can show signs of lameness.
If the tumor has spread to the lungs, symptoms such as coughing and difficult breathing may arise.
Diagnosis of Bladder Cancer in Dogs
As mentioned above, symptoms of canine bladder cancer are similar to other bladder problems such as bladder stones or infections.
So, as a first step, the vet will do a series of tests (such as complete blood count (CBC), biochemistry profile, urinalysis, urine culture, and bladder imaging) to rule out other possible bladder problems.
If the tests rule out other bladder or urinary tract problems and cancer is suspected, the vet will do a tissue biopsy, which is the only way to get a definitive diagnosis.
Once the vet has made a definitive diagnosis of bladder cancer, the next step is to perform “tumor staging”. This staging is to determine the stage (extent) of the disease in order to decide on the most appropriate treatment program.
The “stage” of the disease is basically determined by three factors – the primary tumor, spread to the lymph nodes, and spread to other organs.
Conventional Treatment of Canine Bladder Cancer
The conventional treatment of choice is chemotherapy.
A common chemotherapy plan is a combination of piroxicam with mitoxantrone. This combination can help in around 40% of dogs and the median survival time is about one year.
Another less aggressive chemotherapy plan is the use of only one drug (usually piroxicam). About 2 dogs in 10 will see improvement and the median survival time is about six months.
Surgery is usually difficult for bladder cancer in dogs because of two main reasons.
First, transitional cell carcinomas are locally aggressive and it is difficult to completely remove all cancer cells with surgery.
Second, the position of the tumor can make surgery difficult or even impossible, especially if the tumor occurs in the neck of the bladder where several vital structures are located.
Radiation may control the growth of the tumor but it has its limitation due to serious complications that can be caused by the treatment, such as a scarred, shrunken bladder, and irritation to surrounding organs.