Key Points

• Symptoms of bladder cancer may mimic a simple bladder infection. These include small, frequent urination, painful urination, bloody urine, or incontinence.   Symptoms will often improve initially if antibiotics are given, but then recur a short time later.  

• Most tumors of the bladder are malignant and classified as a transitional cell carcinoma.

• Ultrasound is helpful for looking at the size of the tumor within the bladder and the size of lymph nodes surrounding the tumor.

What is it?

• Cancer of the bladder is most commonly of a type called transitional cell carcinoma (TCC).   This is a tumor of the cells that line the urinary bladder.   Other types of tumors can occur in the bladder, but are rare.
• Inflammatory polyps may also be a cause of bladder masses; these are benign
• TCC can also arise in the kidney, ureters, urethra, prostate, or vagina.   Once developed in an organ it can spread (metastasize) to the lungs, lymph nodes, bones or other organs.   About 20% of dogs with bladder cancer have metastases by the time they are diagnosed.
• Bladder cancer is much more common in dogs than cats, but even in dogs accounts for less than 1% of reported cancers.
• TCC can occur in any breed but is most common in Shetland sheepdogs, Scottish terriers, Airedale terriers, collies, and beagles.   Middle-aged or elderly female dogs are most commonly affected.
• Some studies have suggested that exposure to certain chemicals (such as some types of pesticides) may increase the risk for a dog to develop bladder cancer.

Anatomy

• The urinary system consists of the kidneys, the ureters, the urinary bladder, and the urethra.
• The kidneys are the organs which filter the blood to remove wastes and correct the electrolyte balance of the body.   The filtered waste becomes urine, and travels to the urinary bladder through the ureters.
• The urine continuously collects in the bladder.   The bladder is able to expand due to the special properties of its lining made of transitional cells.   When an animal urinates the urine is voided from the body through the urethra.

Clinical signs

• The symptoms of bladder cancer can be similar to those seen with urinary tract infections. If lymph nodes in the abdomen become enlarged enough you may notice straining to defecate.   Spread of tumor to bones can cause bone pain at these sites.
• Many times animals with bladder cancer do not have any symptoms that can easily differentiate the disease from a simple bladder infection.   In other animals the tumor may be felt during abdominal palpation by your veterinarian.   If the tumor has spread to lymph nodes within the abdomen they may feel enlarged when your veterinarian does a rectal exam.
• 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 and build up of waste products in the body.   Complete inability to urinate is a medical emergency and should be seen by a veterinarian immediately.

Diagnosis

• Urinalysis: Pets with bladder cancer sometimes have cancer cells found in their urine.   However, inflammation of the urinary tract from an infection can create similar-looking cells so this test is rarely diagnostic for bladder cancer.   However, it does check for secondary infections of the bladder (due to the tumor) and help evaluate the health of the kidneys.
• Bloodwork: Bloodwork is often normal in pets with bladder cancer unless the kidneys have become affected.   In that case your veterinarian may find that your pet has evidence of kidney dysfunction.   Bloodwork is also important because it helps evaluate your pet’s overall health which may affect which treatment option is best for them.
• Veterinary bladder tumor antigen (VBTA) test: This is a newly introduced test run on urine to screen for bladder tumors in dogs.   Occasionally dogs without bladder cancer will test positive for VBTA, especially if there is a bladder infection.
• Abdominal Imaging: Bladder tumors are rarely evident on normal x- rays, however spread of tumor to the bones may be evident.   Sometimes special dye studies ( cystograms) can be done to make the tumors visible on x-rays.   This study is especially helpful if your veterinarian suspects that the tumor may be invading your pet’s urethra.   Another way to image the abdomen is with ultrasound.   Ultrasound is helpful for looking at the size of the tumor within the bladder and the size of lymph nodes surrounding the tumor.
• Chest Imaging: Since bladder cancers can spread to the lungs your veterinarian may take chest x-rays to check for metastases.  
• Biopsy: To definitively diagnose TCC of the bladder a sample of cancerous cells must be evaluated.   This is usually done with either a surgical biopsy or from cells collected through an ultrasound-guided urinary catheter.   This biopsy will be sent to a pathologist to examine under a microscope.

Treatment

• Surgery : Surgical removal of the entire tumor is rarely possible.   This is because in dogs the tumor usually arises where the ureters and urethra enter the bladder and surgery would disrupt these vital structures.   Occasionally the tumor arises elsewhere in the bladder (especially in cats) and surgery can remove all or most of the tumor.   When the tumor is only reduced in size at surgery this is called “ debulking”.   Although it may temporarily relieve symptoms for the pet, the tumor will regrow.
• Chemotherapy : Unfortunately, a chemotherapy protocol that works well for bladder cancers in pets has not yet been found.   Less than 20% of pets will respond to the intravenous chemotherapy protocols currently used.   An oral anti-inflammatory drug called piroxicam ( Feldene) also been show to have some anti-cancer activity and may help some dogs.
• Radiation Therapy : Radiation therapy can be helpful in some patients with bladder cancer.   Although some studies suggest it works better than chemotherapy it can have serious side effects (see below).

Potential complications

• Recurrent urinary tract infections and incontinence are common in dogs with TCC of the bladder.
• As bladder cancers enlarge in size they can obstruct the flow of urine.   Inability to urinate is a medical emergency.   When this complication is anticipated and a pet is otherwise healthy a procedure called a “tube cystotomy placement” can be considered.   This involves surgically placing a tube that goes from the urinary bladder to outside the pet’s body through which urine can be emptied.   Management of these tubes requires significant nursing care at home to regularly empty urine and prevent infections.
• Transitional Cell Carcinomas can spread to the lymph nodes, lungs, and bones.   If lymph nodes become greatly enlarged they can cause difficulty defecating.
• Chemotherapy can cause bone marrow suppression leading to anemia and increased susceptibility to infections.   Both chemotherapy and piroxicam can cause GI side effects such as vomiting, diarrhea, or GI ulcers.
• Radiation therapy can have side affects such as narrowing the urethra (causing blockage) or incontinence.

Aftercare

• Pets with TCC of the bladder must be monitored closely at home for bladder infections (secondary to the tumor) or inability to urinate.
• Pets on chemotherapy or radiation therapy will need regular hospital stays for treatment.   Pets on chemotherapy and piroxicam need frequent rechecks of their bloodwork to evaluate their kidney function.   Repeated abdominal imaging studies are needed to follow the progress of the tumor and evaluate the effect of therapies.
• Pets with tube cystotomstomy require careful nursing care at home to keep their bladder emptied and their surgery site clean.

Prognosis

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

References

• Forrest, LJ. “Diagnostic Imaging in Cancer Staging” in Proceedings from Fundamental Approach to the Cancer Patient.   2002.
• Henry, CJ. “What’s New in the Diagnosis and Treatment of TCC of the Bladder” in Proceedings from the Tufts Animal Expo. 2002.
• Higginbotham, ML. “Canine Bladder Cancer” in Proceedings from the Western Veterinary Conference. 2003.
• Tilley LP & Smith FWK, eds. “Transitional Cell Carcinoma, Renal, Bladder, Urethra” in The 5-Minute Veterinary Consult Canine and Feline, 2 nd ed.   Lippincott Williams & Wilkins. 1997.