A polyp is a projecting growth of tissue from the wall of a hollow space, such as the intestines (see also Polyps of the Colon and Rectum). Familial adenomatous polyposis occurs in 1 in 8,000 to 14,000 people. The polyps are present in 50% of people by age 15 and in 95% of people by age 35. In nearly all untreated people, the polyps develop into cancer of the large intestine or rectum (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 of familial adenomatous polyposis are the same as with other colonic polyps (see symptoms of polyps of the colon and rectum). 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 of familial adenomatous polyposis.
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 familial adenomatous polyposis may be tested for a type of liver cancer (hepatoblastoma) from birth until 5 years of age.
Because nearly all people with familial adenomatous polyposis develop cancer, doctors typically recommend surgery be done soon after the diagnosis is made. There are several procedures. Complete removal of the large intestine and rectum (called total colectomy or proctocolectomy) 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 somewhat 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, which could then turn into cancer. Thus the remaining part of the rectum must be inspected by sigmoidoscopy frequently, 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. Doctors may also recommend people have their thyroid screened every year.
Some 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.