Polyps are small growths on the inner colon lining that look like warts. It is not known exactly how polyps form, but it has to do with changes that occur as the colon's old inner lining gets rubbed off and new lining grows. If the old lining does not get rubbed off quickly enough, or the new lining grows in too fast, polyps can form. Genetic changes in cells cause normal colon lining to turn into polyps.

An illustration of a polyp on the colon's inner liningPolyps may turn into colon cancer which can possibly spread to the rest of the body. Removing colon polyps can prevent colon cancer. Polyps are removed during a colonoscopy without the need for surgery.

Removing a polyp and looking at it under a microscope is the only way to identify the polyp type, which includes:

  • inflammatory polyps — forms in reaction to ulceration or irritation; often seen in cases of colitis; will not turn into cancer.
  • hyperplastic polyps — also have a very low risk of turning into cancer.
  • adenomatous polyps — may eventually become cancerous; should have repeat colonoscopies every three years to look for, and remove, any new polyps.
  • villous polyps — aggressive and more likely to turn into cancer; should be removed completely when found; require a colonoscopy one year after they are removed, and then every one to three years after that; occasionally so large that they must be removed with surgery.

A few people develop many, many polyps in their colon. This is called polyposis coli. Hundreds, even thousands, of polyps can occur. This condition tends to run in families. If a mother or father has polyposis coli, chances are that about half of their children will have it. If these polyps are not treated and removed, nearly all individuals with this condition will develop cancer of the colon or rectum by the time they are 40 years old. The treatment for polyposis coli is removal of the colon and creation of a new rectum using the small intestine.