Making a firm diagnosis of colorectal cancer is usually relatively easy. A barium enema or colonoscopy can show the position of a cancer within the bowel. In addition, a small piece of tissue can be taken for microscopic analysis at the time of colonoscopy. The main treatment for colorectal cancer is surgical removal of the tumor. In the past, many operations involved the formation of a colostomy , which meant wearing a bag on the abdominal wall to collect bowel movements.
Most operations involve removal of the cancer and a section of bowel on either side.
Interestingly, most patients retain very good control of bowel movements, even when a large section of the colon is removed. Following the operation, the removed bowel and cancer will be examined microscopically by a pathologist. The pathologist can then tell how far the tumor has penetrated through the bowel and surrounding tissues, if lymph nodes are involved and if the tumor has reached the edge of the surgical specimen. In stage II, the tumors extend past the bowel wall but do not involve lymph nodes. Stage III tumors have cancer cells present in lymph nodes, and stage IV cancers have spread to distant sites such as the liver.