Bladder Cancer in Dogs

What Is Bladder Cancer in Dogs?

Cancer can develop in a dog’s urinary tract, including in the kidneys, ureters, prostate, and urethra. However, cancer of the urinary tract in dogs most commonly occurs in the bladder. Bladder cancer in dogs typically grows quickly and can metastasize (spread) to other parts of a dog’s body.

While bladder cancer constitutes only about 2% of canine cancers, the condition is usually incurable and causes significant problems for affected dogs.

Bladder cancer types that affect dogs include transitional cell carcinoma (TCC) and leiomyosarcomas (LMS), with TCC being by far the most common.

Transitional cells line the urinary bladder, protecting a dog’s body from the urine’s harsh chemicals in the urine. In dogs, TCC develops from these cells and often also invades the deeper bladder structures, including the muscle layers, which may also affect the kidneys, ureters, prostate (in males), and urethra.

As the cancer grows, urine flow can become obstructed, and the cancer can spread to the dog’s lymph nodes and other organs.

Symptoms of Bladder Cancer in Dogs

Bladder cancer symptoms are similar to those seen in dogs affected by urinary tract infections and other urinary tract conditions. Bladder cancer signs include:

• Blood in the urine

• Straining to urinate

• Frequently urinating small amounts

• Urinary accidents

Causes of Bladder Cancer in Dogs

Most causes of bladder cancer in dogs can’t be identified. However, certain factors increase a dog’s risk of bladder cancer, including:

• Age—Bladder cancer is more common in dogs 10 years of age and older.

• Sex—Female dogs have a higher TCC risk than male dogs, possibly because they urine mark less frequently and therefore toxins stay in the urinary bladder longer.

• Breed—Scottish Terriers have an 18- to 20-fold higher TCC risk than other dog breeds, while Shetland Sheepdogs, Beagles, West Highland Terriers, and Wire Hair Fox Terriers have a three- to five-times higher risk than other dog breeds.

• Body condition—Obese and overweight dogs have an increased risk of developing bladder cancer.

• Chemotherapy—Certain chemotherapy treatments can cause bladder cancer in dogs.

• Environmental factors— 

  • Certain pesticides and insecticides—such as those found in flea dips used in the past—have been linked to bladder cancer. Exposure to lawn herbicides and pesticides may also be a contributing factor.

  • Additionally, some studies suggest that secondhand smoke can increase a dog’s bladder cancer risk. This is attributed to the carcinogens (cancer-causing substances) found in tobacco smoke, which, when inhaled, can be absorbed into the bloodstream. Once excreted in urine, these substances directly affect the bladder, potentially leading to damage and an elevated risk of bladder cancer.

How Veterinarians Diagnose Bladder Cancer in Dogs

Because other urinary tract issues can cause symptoms similar to bladder cancer, your veterinarian will need to perform a bladder tissue biopsy to make a definitive diagnosis. Other tests your vet may recommend include:

• Blood work—Blood work, including a complete blood count (CBC) and biochemistry profile, can help assess your dog’s overall health and detect infection and kidney abnormalities.

• Urinalysis and culture—Urinalysis and urine culture are important to rule out a urinary tract infection and other potential urinary tract issues such as bladder stones.

• X-rays—X-rays can detect bladder stones. However, they can’t detect bladder tumors unless your veterinarian administers a special contrast dye to your dog.

• Ultrasound—Ultrasound is a noninvasive way to visualize stones, polyps, and tumors inside the bladder.

• BRAF mutation test—A urine test is available that detects a specific mutation in the BRAF gene. However, this test isn’t always accurate.

• Antibiotic trial—Before performing a urinary bladder biopsy, your veterinarian may recommend an antibiotic trial to see if your dog’s signs resolve with treatment.

If your dog is diagnosed with bladder cancer, your vet may perform tumor staging to determine the prognosis and how best to treat the condition.

Your vet will typically repeat tumor staging tests during your dog’s treatment to determine whether the prescribed treatment is working or the disease is progressing. Your vet can stage your dog’s tumor using:

• X-rays—Your vet will perform chest and abdominal X-rays to look for tumor changes or growth, including spread to new areas (i.e., metastasis).

• Ultrasound—Abdominal ultrasound helps determine the tumor’s location and size, as well as kidney abnormalities that may result from obstructed urine flow.

Treatment of Bladder Cancer in Dogs

Bladder cancer treatment depends on the tumor’s size and location, and if metastasis has occurred. Bladder cancer treatment options may include:

• Surgery—For a small tumor that isn’t close to the bladder neck, surgery may be possible. The bladder neck is a muscular region where the bladder connects to the urethra, and it acts as a valve that helps control the release of urine from the bladder.

  • During this procedure, a margin of normal tissue around the tumor is removed to prevent tumor regrowth. Unfortunately, most TCCs in dogs are located in the bladder neck, and surgery is usually not possible.

• Radiation—In the past, radiation therapy for bladder cancer often caused side effects such as a scarred, shrunken bladder or irritation to a dog’s surrounding organs. However, advanced imaging available at specialty hospitals can allow veterinarians to better target a tumor.

• Nonsteroidal anti-inflammatory drugs (NSAIDs)—NSAIDs are typically used to alleviate pain, but these drugs also seem to have anti-cancer effects. In one study, dogs given the NSAID piroxicam exhibited good results, including 3% of dogs who experienced complete remission, 14% of dogs whose tumor size shrunk by more than 50%, and 56% of dogs who experienced no tumor growth during the study period. NSAIDs can be used alone or combined with more aggressive chemotherapy drugs.

• Chemotherapy—Chemotherapy drugs (systemic) are often used to treat bladder cancer in dogs. These drugs tend to have only mild side effects.

• Antibiotics—Bladder cancer increases a dog’s urinary tract infection risk. Your veterinarian can manage these infections with antibiotics.

• Stents—If a bladder tumor obstructs your dog’s urine outflow, your veterinarian may recommend placing a stent in the urethra to restore your dog’s urine flow.

Recovery and Management of Bladder Cancer in Dogs

Regardless of treatment, your veterinarian will likely monitor your dog every four to eight weeks to assess the treatment’s efficacy. During this time, dogs may have urinary accidents at home, and puppy pads may be useful to facilitate cleanup.

In most cases, bladder cancer is incurable, but treatment can allow a dog to live longer and enjoy a better quality of life than without treatment. The prognosis depends on the tumor’s size, growth rate, and location, and whether the cancer has spread.

Survival times vary widely, with some dogs living only a few days after diagnosis and some living two years or longer.

Prevention of Bladder Cancer in Dogs

Steps to decrease a dog’s bladder cancer risk include:

• Avoid older-generation flea control products such as flea dips.

• Avoid treating your lawn with herbicides and pesticides.

• Keep your dog at a healthy body weight.

• Feed your dog yellow or orange vegetables and leafy greens at least three times a week, as these are rich in vitamins, minerals, and antioxidants.

• Eliminate your dog’s exposure to tobacco smoke—don’t smoke in the house.