Overview of Canine Urinary Bladder Cancer
The most common bladder tumor in dogs is a malignant tumor called transitional cell carcinoma. This cancer usually arises from the inside surface of the urinary bladder or urethra and less commonly from the muscular wall of the urinary tract. Transitional cell carcinoma accounts for 0.5 percent of all cancers in dogs.
The cause of transitional cell carcinoma is unknown, but carcinogens, or cancer causing chemicals, that are excreted in the urine may cause the cells that line the bladder and urethra to become cancerous. Exposure to insecticide dips applied to kill fleas and ticks may increase the risk of developing this type of cancer. Similarly, exposure to sprays used to control mosquitoes in marshy or wetland areas also may increase risk.
Cyclophosphamide, a drug used to treat cancer and certain immune diseases, is metabolized to a carcinogenic chemical called acrolein, which is excreted in the urine. Exposure to cyclophosphamide may increase a pet’s risk for development of urinary bladder cancer.
Breeds predisposed or reported to be at a higher risk for bladder cancer include Shetland sheepdogs, Scottish terriers, West Highland white terriers, beagles and wirehaired fox terriers.
Female dogs are affected more commonly than males. Neutered dogs are at a higher risk than are intact dogs. Obesity also may predispose to development of this type of cancer.
Urinary bladder cancer is life-threatening. Left untreated, it can result in obstruction of the urinary tract and inability to urinate. This form of cancer can also metastasize, or spread to other parts of the body. At the time of diagnosis, transitional cell carcinoma is estimated to have spread in more than 50 percent of dogs in which it is diagnosed. Survival of dogs with this type of cancer is dependent on the location of the tumor in the bladder, extent of disease and whether it has metastasized, and what treatments are prescribed. Survival time can range from weeks to more than a year.
What to Watch For
Signs of urinary bladder cancer in dogs may include:
Blood in the urine
Straining to urinate
Increased frequency of urination with passage of small amounts of urine
Straining while defecating
Signs of exercise intolerance
Difficulty breathing or coughing
In many cases, these signs can be present for many months before diagnosis. If your pet is showing any of these signs and does not seem to be getting better with treatment, additional tests should be done to rule out cancer as the cause.
Diagnosis of Urinary Bladder Cancer in Dogs
Diagnostic tests are needed to recognize urinary bladder cancer and exclude other diseases. Tests may include:
Complete medical history and physical examination including rectal examination to palpate the urethra, bladder neck, male prostate gland and local lymph nodes
Plain X-rays of the abdomen to evaluate for masses and lymph node enlargement and of the chest to evaluate for metastasis
Complete blood cell count
Serum biochemistry tests to evaluate your pet’s general health, other body systems, and to identify metabolic consequences of urinary obstruction
Urinalysis to evaluate for white cells, red cells, bacteria or tumor cells
Cytology examination of urine to evaluate for tumor cells
Abdominal ultrasound examination to evaluate the location and extent of the bladder tumor, the status of regional lymph nodes, and the presence of obstruction of the urinary tract
Contrast dye X-ray studies to evaluate the location and extent of the bladder tumor in the place of abdominal ultrasound examination
Urethrocystoscopy by passing a rigid or flexible scope into the urethra and bladder under anesthesia to identify the location and extent of the tumor. This procedure allows for biopsy of the tumor, but usually requires referral to a veterinary specialist.
A relatively new test called V-TBA has become available to screen for the presence of a bladder tumor marker in the urine of dogs suspected to have transitional cell carcinoma.
Treatment of Urinary Bladder Cancer in Dogs
Your veterinarian may refer you to a veterinary cancer specialist (oncologist) to discuss treatment options. Treatment for urinary bladder cancer may include one or more of the following:
Surgery for small masses confined to certain locations in the body of the urinary bladder. Unfortunately, many transitional cell carcinomas are found in parts of the bladder that are not amenable to surgery.
Cancer chemotherapy for some dogs with transitional cell carcinoma
The non-steroidal anti-inflammatory drug piroxicam (Feldene®) has show some promise in symptomatic treatment of some dogs with transitional cell carcinoma. In one study, tumors regressed in approximately 25 percent of treated dogs, remained stable and did not grow in 50 percent of treated dogs, and progressed in 25 percent of treated dogs.
Home Care and Prevention
Evaluation for cancer of the urinary bladder is warranted if you have an older dog and notice blood in the urine, increased frequency of urination, and straining to urinate that either does not respond to routine treatment with antibiotics or that resolves only to return after stopping antibiotic treatment.
You should seek veterinary care immediately if you suspect that your pet is unable to urinate. Inability to urinate leads to severe metabolic complications called uremia within less than three days of complete urinary obstruction.
Watch your pet closely for changes in urinary habits after diagnosis has been made and treatment begun, because such changes may indicate additional tumor growth.
Avoid dipping your dog with flea and tick control products more than two times per year due to possible increased risk of developing bladder cancer. If you live in an area of the country where fleas and ticks are a year-round problem, talk to your veterinarian about alternative forms of flea and tick control.
Obesity may predispose your pet to this type of cancer. Regular exercise and diet control are recommended for the general health of your pet.
In-depth Information on Urinary Bladder Cancer in Dogs
Other diseases may cause symptoms similar to those of urinary bladder cancer. Examples include:
Bacterial lower urinary tract infection (UTI or cystitis). Bladder infections are relatively common in dogs and cause signs similar to those seen with bladder cancer. Bacterial cystitis is more common in females than males. Diagnosis is made by evaluating results of urinalysis and bacterial culture and sensitivity of the urine. Animals with bladder cancer can develop bacterial UTI because the bladder’s natural defenses have been damaged, and bladder cancer should be considered in older dogs that have repeated episodes of UTI or UTI that does not respond to appropriate antibiotic treatment.
Cystic calculi (bladder stones). Bladder stones are relatively common in dogs and cause signs similar to those seen with bladder cancer. Bladder stones irritate the lining of the bladder blood in the urine, straining to urinate and increased frequency of urination.
Benign tumors of the bladder. Polyps and other benign growths such as leiomyomas, which are benign tumors of smooth muscle, can occur in the bladder but are quite rare. Such masses may be removed by surgery and do not usually return.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
In-depth Information on Diagnosis
Diagnostic tests are needed to identify urinary bladder cancer, exclude other diseases and determine the impact of bladder cancer on your pet. Tests may include:
Complete medical history and thorough physical examination including rectal examination to evaluate the urethra, bladder neck, prostate gland in males and local lymph nodes.
Abdominal and chest X-rays to evaluate for abnormalities of the bladder, enlargement of local lymph nodes and spread of cancer to the lungs. It is not unusual for bladder cancer to spread to the local lymph nodes in the abdomen.
Complete blood cell count (CBC) to evaluate red cells, white cells, and platelets, which are responsible for normal blood clotting. The CBC is a standard screening test to assess your pet’s general heath and insure that it is safe to perform other procedures, such as surgery, on your pet. The presence of anemia may suggest longstanding or severe blood loss or a chronic disease process.
Serum biochemistry tests to evaluate your pet’s general health, assess the function of other organs such as the liver and kidneys and identify electrolyte and acid base disturbances.
Urinalysis to evaluate for the presence of white cells, red cells, bacteria and crystals. Occasionally, bladder tumor cells can be identified by microscopic examination of the urine. Kidney function can be evaluated by a test of urine concentration called “specific gravity.”
Abdominal ultrasound to evaluate for tumors in the bladder and urethra, stones in the urinary tract, or urinary tract obstruction. Ultrasound examination allows internal structures to be evaluated on a monitor as ultrasonic waves are transmitted to and reflected from tissues. Ultrasound is a specialized procedure that may require referral to a veterinary specialist. It is not painful to your pet and is tolerated well by most dogs. It does require that some of the pet’s hair be shaved from the abdomen.
Special contrast X-ray studies to evaluate for bladder tumors, stones, or urinary tract obstruction. Radiographic dye is called “positive” contrast because it appears white on the X-ray, and air is called “negative” contrast because it appears black on the X-ray. Either can be introduced into the bladder via the urethra to evaluate for bladder tumors. Such a study is called a urethrocystogram.
Cystoscopy to evaluate the urethra and bladder for stones, tumors or congenital defects. Cystoscopy is a specialized test in which a flexible or rigid scope is passed into the urethra and bladder for direct visualization while the pet is under general anesthesia. This test typically requires referral to a veterinary specialist. It allows bladder tumors to be identified by their characteristic “frond-like” appearance and allows biopsy samples to be taken for pathologic analysis.
The V-TBA, or urinary tumor bladder antigen, test has been developed recently to allow identification of tumor markers in urine.
In-depth Information on Treatment
Treatment of bladder cancer rarely is curative and more often is used with the intention of controlling the disease temporarily, relieving partial urinary tract obstruction, and making the pet more comfortable for a variable period of time. Such an approach will usually improve your pet’s quality of life and allow you to spend more time with your pet. Unfortunately, bladder cancer usually is very advanced in dogs by the time it is diagnosed. Often, it already has metastasized to local lymph nodes in the abdomen.
Treatment for bladder cancer may include one or more of the following:
Surgery. Small masses confined to the fundus or body of the bladder can be removed surgically. Despite this, the cancer can appear in other areas of the bladder. Also, bladder tumors that affect the region of the bladder into which the ureters empty (called the trigone), the bladder neck, and first portion of the urethra are not accessible for surgery. For these reasons, surgery often is not recommended for many pets with bladder cancer. Surgery, however, can serve as a diagnostic tool to obtain biopsy specimens of bladder masses or, in advanced cases, to place a tube in the bladder that comes out the through the abdominal wall allowing the owner to drain the animal’s bladder manually several times a day as needed. This is a cystostomy tube.
Cancer chemotherapy. Treatment protocols using anti-cancer drugs can be used to manage pets with bladder cancer. These drugs are often very toxic, resulting in adverse effects such as bone marrow suppression leading to low white cell count, gastrointestinal toxicity with nausea and vomiting, and kidney toxicity. A specialist in veterinary oncology should be consulted about chemotherapy for bladder cancer. Examples of some anti-cancer drugs used in dogs with bladder cancer include cisplatin, carboplatin, and mitoxantrone. Remissions of six months and sometimes longer have been achieved with chemotherapy.
Piroxicam (Feldene®) is a non-steroidal anti-inflammatory drug that has been used to treat pets with bladder cancer. Its mechanism of action is not well understood but partial remission occurs in 25 percent of treated dogs, stabilization of disease occurs in 50 percent and, unfortunately, progression of disease occurs in 25 percent of treated dogs. The main toxicity of piroxicam is gastrointestinal upset.
Radiation therapy can be used to treat some bladder cancers by directing a beam of radiation at the affected area and sites of metastasis. Radiation therapy is a highly specialized form of treatment available only at selected referral centers and teaching institutions. Radiation therapy is associated with adverse effects because overlying skin and surrounding tissues also can be damaged by the radiation. A veterinary oncologist should be consulted about the advisability of radiation therapy for your pet’s bladder cancer.
Follow-up Care for Dogs with Urinary Bladder Cancer
Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be crucial.
Administer any prescribed medications as directed by your veterinarian and contact your veterinarian if you experience difficulty treating your pet.
Activity should be restricted in the postoperative period while your pet is recovering from surgery to obtain a biopsy, remove a tumor, or place a cystostomy tube to allow proper healing of the surgery site. Your pet may need to have sutures removed from the skin 10 to 14 days after surgery.
Results of the biopsy report will help your veterinarian decide the optimal treatment approach for your pet.
If you consult a veterinary oncologist and begin chemotherapy for your pet, you will need to watch for signs of toxicity and to evaluate your pet’s ability to urinate more normally. A schedule of follow-up visits will be designed to evaluate your pet’s response to treatment using tests such as ultrasound examination, contrast X-ray studies and occasionally cystoscopy.
Signs to watch for that may indicate that cancer has progressed or spread include: straining to urinate or defecate, decreased activity, shortness of breath, coughing, and decreased appetite. Signs such as loss of appetite, fever, vomiting or diarrhea also may indicate toxicity associated with chemotherapy. Contact your veterinarian or veterinary oncology specialist if you observe any of these signs.
Prevention of Urinary Bladder Cancer in Dogs
Avoid dipping your dog with insecticides used to control fleas and ticks more than two times per year due to a statistical association of such products with increased risk of bladder cancer. If you live in an area of the country where fleas and ticks are a year-round problem, talk to your veterinarian about alternative forms of flea and tick control.
Proper diet and regular exercise are important for your pet, and a statistical association of obesity and bladder cancer in dogs has been identified.
Breeds such as the Shetland sheepdogs, Scottish terriers and West Highland white terriers have increased risk for bladder cancer and should be observed carefully as they age for potential signs of bladder cancer, such as blood in the urine, straining to urinate and increased frequency of urination.
Exposure to the drug cyclophosphamide used to treat cancer and some immune-mediated diseases and its carcinogenic breakdown product (acrolein) has been incriminated in development of bladder cancer. Pets that have been treated with this drug should be monitored for potential signs of bladder cancer like blood in the urine, straining to urinate and increased frequency of urination.