The rectum is the lowest part of the large intestine. It lies immediately above the anus. Cancer of the rectum is uncommon before the age of 40. But in later years, together with cancer of the colon, it is second only to cancer of the lung as a cause of death in Britain. Over 70 per cent of large-intestine cancers occur in the rectum and lower colon (sigmoid colon). Rectal cancers may be of three types:

• Ring growths, all around the bowel, which narrow it
• Growths like little mushrooms (polyp-like) that protrude into the bowel
• Growths that eat into the wall (ulcers).

Rectal cancers may spread through the bowel wall to the lining membrane of the abdomen (peritoneum). They may spread to the local or distant lymph nodes (glands). They may also spread remotely, by way of the bloodstream, to other parts of the body.

Diagnosis

The diagnosis is made on the basis of the symptoms, the appearance of the stools, feeling the cancer area with a gloved finger during a rectal examination, direct examination of the inside of the rectum with a viewing tube called a sigmoidoscope, and the taking of a small piece of the suspected cancerous tissue for microscopic examination (biopsy).

Treatment

Rectal cancer is treated by a surgical operation to remove the affected segment of the bowel. The free ends are then joined together, if this is possible.

When the cancer is very low in the rectum, the anal canal must also be removed to prevent the cancer coming back. In that case an artificial opening (colostomy) is necessary, bringing the bowel out through the front wall of the abdomen.