Noncancerous growths in the large intestine that often do not produce symptoms
Polyps in the colon are very common in developed countries, where at least 1 in 3 people over the age of 60 may be affected. However, most people are unaware that they have polyps because they often do not cause symptoms.
Polyps are slow-developing growths that protrude inwards from the lining of the large intestine. Some are small and spherical and are attached directly to the intestinal wall; others are over 2.5 cm (1 in) long and attached to the wall by a stalk. Polyps can occur either singly or in groups. Growths larger than about 1 cm (
In most cases, the cause of the condition is not known. Rarely, polyps result from an inherited condition such as familial adenomatous polyposis (FAP). This condition, in which hundreds of polyps cover the lining of the large intestine, is due to an abnormal gene inherited in an autosomal dominant manner (see Gene disorders).
In most cases, intestinal polyps do not cause symptoms. However, if symptoms do occur, they may include:
Blood in the faeces or bleeding from the anus, sometimes with mucus.
In some cases, anaemia develops due to blood loss, causing tiredness and shortness of breath. In rare cases, a polyp protrudes through the anus.
In many people who do not have symptoms, polyps may be detected during routine screening for colorectal cancer or by investigations that are performed for other reasons. If you do have symptoms, your doctor may arrange for a colonoscopy to examine the lining of the intestine. Most polyps can be removed painlessly during the colonoscopy, but occasionally surgery may be necessary to remove larger growths. Polyps that have been removed will be examined under a microscope to look for precancerous cells. If you are found to have precancerous polyps, you may need a colonoscopy every 3–5 years to check for new growths.
If you have FAP, the polyps will be too numerous to be removed individually. There is a high risk of colorectal cancer associated with FAP, and for this reason you will probably be advised to have your colon completely removed (see Colectomy). If you have a close relative with FAP, you may be offered regular screening using colonoscopy to look for polyps. In some cases, testing for the abnormal gene that causes FAP may be carried out. If no polyps have developed by the time you reach the age of 40, they are unlikely to occur.
Polyps that do not cause any symptoms may never be diagnosed, although they may sometimes be detected during a faecal occult blood screening test for colorectal cancer. Those polyps that do cause symptoms can almost always be treated successfully. In such cases, further polyps may develop. However, with treatment the condition can be controlled and the risk of colorectal cancer kept to a minimum.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.