There are two common types: hyperplastic polyp and adenoma. The hyperplastic polyp is typically not at risk for cancer. The adenoma, however, is thought to be the precursor (origin) for almost all colon cancers, although most adenomas never become cancers. Histology (examination of tissue under a microscope) is the best way to differentiate between hyperplastic and adenomatous polyps. Although it’s impossible to tell which adenomatous polyps will become cancers, larger polyps are more likely to become cancers and some of the largest ones (those larger than 1 inch) can already contain small areas of cancer. Because your doctor cannot usually be certain of the tissue type by the polyp’s appearance, doctors generally recommend removing all polyps found during a colonoscopy.
Most polyps cause no symptoms. Larger ones can cause blood in the stool, but even they are usually asymptomatic. Therefore, the best way to detect polyps is by screening individuals with no symptoms. Several other screening techniques are available: testing stool specimens for traces of blood, performing sigmoidoscopy to look into the lower third of the colon or using a radiology test such as a barium enema or CT colonography.
If one of these tests finds or suspects polyps, your doctor will generally recommend colonoscopy to remove them. Because colonoscopy is the most accurate way to detect polyps, many experts now recommend colonoscopy as a screening method so that any polyps found or suspected can be removed during the same procedure.
Most polyps found during colonoscopy can be completely removed during the procedure. Various removal techniques are available; most involve removing them with a wire loop, biopsy forceps and/or burning the polyp base with an electric current. This is called polyp resection. Because the bowel’s lining isn’t sensitive to cutting or burning, polyp resection doesn’t cause discomfort. Resected polyps are then examined under a microscope by a pathologist to determine the tissue type and to detect any cancer. If a large or unusual looking polyp is removed or left for possible surgical management, the endoscopist may mark the site by injecting small amounts of sterile India ink or carbon black into the bowel wall. This is called endoscopic tattooing.
Polyp removal (or polypectomy) during colonoscopy is a routine outpatient procedure. Possible complications, which are uncommon, include bleeding from the polypectomy site and perforation (a hole or tear) of the colon. Bleeding from the polypectomy site can be immediate or delayed for several days; persistent bleeding can almost always be stopped by treatment during another colonoscopy.Perforations rarely occur and may require surgery to repair.