Diagnosis
Bladder tumors tend to occur in older female dogs, and certain breeds such as West Highland White Terriers and Scottish Terriers might be predisposed. The majority of bladder tumors are carcinomas, and the majority of these are transitional cell carcinomas. Affected dogs usually have symptoms such as blood in the urine, straining to urinate, and increased frequency of urination. Many affected dogs have secondary urinary tract infections.
Diagnosis is best achieved with a biopsy sample. This sample can be obtained surgically (through a procedure called a cystotomy) or by using a cystoscope. A cystoscope is either a rigid or flexible tube that can be passed into the bladder through the urethra and through which pictures of the tumor and small pieces of tissue can be obtained. Alternatively, fine needle aspirates obtained through the body wall using ultrasound guidance can be submitted for a cytological diagnosis.
In some cases, a diagnosis can be obtained through a cytological evaluation of a urine sample, since cancer cells are sometimes shed into the urine in enough numbers to allow for a diagnosis. However, this can be difficult if there is a large amount of blood, inflammation, and/or bacteria in the urine. Similarly, there is a "bladder tumor antigen test" that detects a molecular complex (a glycoprotein antigen) produced by bladder tumors. However, this test is unreliable if there is a lot of blood or inflammatory cells in the urine. In these cases, the result can be a "false positive", meaning that the test suggests the presence of cancer when no cancer is in fact present. On the other hand, if the test is negative, it is relatively unlikely (although still possible) that a bladder carcinoma is present.
Causes
The exact cause of dog bladder cancer is unknown. However, cancer causing chemicals (carcinogens) excreted in the urine may cause the cells on the bladder and urethra walls to become cancerous.
Treatment
Treatment for most bladder tumors is palliative, which means it is directed at minimizing symptoms and prolonging a good quality of life. Bladder tumors are usually large and invasive at the time of diagnosis, and even when there appears to be a solitary lesion that might be amenable to surgery, postoperative recurrence is very common.
Prognosis
Bladder cancer in dogs usually has a poor prognosis because about 50% of dogs are being diagnosed too late - at the time of diagnosis, the cancer has already spread (metastasis) to other parts of the body, such as the pelvis, the lumbar vertebrae, and regional lumph nodes. Depending on the location of the tumor in the bladder, and whether it has metastasized, survival time can range from weeks to more than a year upon diagnosis. If untreated, canine bladder cancer can result in complications from urinary tract obstruction such as inability to urinate, and/or metastases, usually within three to six months.
