Dogs can get many types of cancers, including colon and rectal cancer. Although dogs of any age can get colon or rectal cancer, it most commonly appears in older dogs, according to Canine Cancer Awareness.
Cancer of the dog's anal sacs is called anal sac adenocarcinoma. Cancers in the dog's colon, liver or spleen are called gastrointestinal lymphosarcoma.
Symptoms can vary for each dog, but common symptoms include constipation, passing blood, hair loss, loss of appetite and loss of energy. Sometimes the dog may seem to have an insatiable thirst, according to veterinarian Dr. Kimberly Cronin.
Surgical removal is necessary to prevent the cancer from spreading, followed up with chemotherapy and radiation, according to "Dog Owner's Home Veterinary Handbook."
The average lifespan of a dog diagnosed with adenosarcoma is nine months, according to Canine Cancer Awareness. But dogs with lymphosarcoma can sometimes be cured.
Dogs can grow what appear to be flesh-coloured grapes in side the rectum and out of the anus. These are called polyps and need to be removed but they are not cancerous, according to "Dog Owner's Home Veterinary Handbook."