Patient Information from CSSANZ Website
What does a polyp look like?
Polyps vary in their shape, size and location within the large bowel. They may be single or multiple. A typical polyp has the appearance of a cherry with a short stalk or pedicle. Most polyps measure about one centimetre in diameter. Some have no stalk and are flat or carpet-like, spreading over the mucosal surface of the bowel.
Adenomatous polyps (adenoma)
There are different varieties of polyps but those which are associated with bowel cancer are termed adenomatous polyps or simply adenomas. This variety of polyp is important because there is strong evidence that some adenomas may undergo malignant change to produce bowel cancer. Patients who are found to have adenomas are considered at risk of developing bowel cancer. This risk is difficult to quantify. It varies from patient to patient and usually requires periodic surveillance by telescopic examination of all of the large bowel (colonoscopy).
Pre-cancer and cancer
Adenomas when pre-cancerous are composed of abnormal, rapidly dividing cells whose suspicious appearance and behaviour can only be accurately recognised by the pathologist when examined under the microscope. Therefore, when polyps are discovered they are best removed (polypectomy) so that they can be carefully examined and classified by a pathologist. It may take up to 12 years for a benign adenoma to become an invasive cancer. Large adenomas (greater than two centimetres in diameter) are always suspected of having developed a small focus of cancer until proven otherwise by the pathologist.
Although polyps are very common, they rarely produce symptoms and usually are discovered by chance at the time of colonoscopy. However, large adenomas occasionally may cause bleeding , usually as blood mixed in the stool.
Who is at risk?
People who have suspicious bowel symptoms (especially bleeding) and are approaching 40 years of age or older, may need a colonoscopic examination. Other people at risk include those with a significant family history of one or more first degree relatives (mother, father, sister, brother or child) who have had bowel cancer. Patients who have had a previous adenoma or cancer successfully treated, have a risk of developing polyps which continues through their life. Familial adenomatous polyposis (fap) is a rare, inherited disorder in which some members of the family will develop hundreds of polyps untimately causing bowel cancer if not treated properly.
Colonoscopy is the most accurate test to diagnose polyps. The purpose is to obtain a clear view of the whole length of the inner surface of the bowel, to search for and remove any polyps found, and have them examined under the microscope. Up to 90% of polyps can be safely and completely removed by colonoscopy.
If adenomas are confirmed by a pathologist, it is recommended that the patient have regular “check-ups” by repeated colonoscopy. The frequency of examinations varies and this needs to be discussed with the doctor who performed the colonoscopy.