Familial adenomatous polyposis is an inherited disorder in which 100 or more precancerous polyps develop throughout the large intestine and rectum during childhood or adolescence. In nearly all untreated people, the polyps develop into cancer of the large intestine or rectum (colorectal cancer—see Tumors of the Digestive System: Colorectal Cancer) by age 40.

People with familial adenomatous polyposis also have an increased risk of developing cancer in the duodenum, pancreas, thyroid, brain, and liver. People with familial adenomatous polyposis can develop other complications (previously termed Gardner syndrome), particularly various types of noncancerous tumors. These noncancerous tumors develop elsewhere in the body (for example, on the skin, skull, or jaw).

Symptoms and Diagnosis

Symptoms and diagnosis of familial adenomatous polyposis are the same as with other colonic polyps (see Tumors of the Digestive System: Symptoms and Diagnosis). Most people have no symptoms but a few have rectal bleeding. Usually the bleeding is only in microscopic amounts. Colonoscopy is done to make the diagnosis.

For people with familial adenomatous polyposis, doctors also recommend genetic testing. Immediate relatives should also have genetic testing. If genetic testing is unavailable, relatives should be screened once a year with sigmoidoscopy (examination of the lower portion of the large intestine with a viewing tube) beginning at age 12 and reducing in frequency with each decade. Children of people with FAP should be tested for a type of liver cancer (hepatoblastoma) from birth until age 5 yr.

Treatment

Because nearly all people with familial adenomatous polyposis develop cancer, doctors typically recommend surgery be done as soon as the diagnosis is made. There are several procedures. Complete removal of the large intestine and rectum eliminates the risk of cancer. Because the person then has no rectum, the cut-off end of the small intestine is permanently attached to a surgical opening in the abdominal wall (ileostomy). Bodily wastes are eliminated through the ileostomy into a disposable bag. As an alternative to ileostomy, sometimes doctors can remove the large intestine and only the lining of the rectum (polyps grow from the lining). Then, they can form the end of the small intestine into a pouch that is connected to the anus. The pouch functions like a rectum, eliminating the need for an ileostomy. As another alternative to ileostomy, only the large intestine is removed and the rectum is joined to the small intestine. This procedure does not eliminate the possibility of rectal polyps developing. Thus the remaining part of the rectum must be inspected by sigmoidoscopy every 3 to 6 months, so that new polyps can be removed. If new polyps appear too rapidly, however, the rectum must also be removed.

After people have their entire rectum and large intestine removed, they should have an endoscopy of the stomach and upper section of the small intestine (duodenum) at regular intervals to look for cancer.

Some nonsteroidal anti-inflammatory drugs (NSAIDs) are being studied for their ability to reverse the growth of polyps in people with familial adenomatous polyposis and in people with polyps or cancer of the large intestine. Their effects are temporary, however, and once these drugs are discontinued, the polyps begin to grow again.

Last full review/revision February 2013 by Elliot M. Livstone, MD