Our pets’ urinary systems function much like those of humans. They consist of the kidneys, the ureters, the urinary bladder, and the urethra. The kidneys filter the blood to remove wastes from the bloodstream, and also maintain the electrolyte, or salt, balance of the body. That waste then becomes urine, and travels through the ureters to the bladder, which is able to expand thanks to the transitional cells that make up its lining and its muscular wall. When an animal urinates, the urine passes out of the body through the urethra.
The most common type of urinary bladder cancer in dogs is transitional cell carcinoma (TCC) - a tumor of the cells that line the bladder. Most tumors are classified as intermediate to high-grade infiltrative bladder tumors at the time of diagnosis.
TCC can also arise in the ureters, urethra, prostate, or vagina and can spread (metastasize) to the lungs, lymph nodes, bones, or other organs. Approximately 20% of dogs with bladder cancer have metastases at the time of diagnosis. Other less common types of tumors of the bladder cancer of the urinary tract may include leiomyosarcomas and fibrosarcomas. Read more about Bladder Tumors - TCC