What is a bowel polyp?
A bowel polyp is an abnormal growth of tissue growing on the wall of the bowel (colon). If polyps are left for many years, a small number may develop into bowel cancer. Bowel polyps can be detected at the time of colonscopy and can usually be removed completely and safely, eliminating the chance for that polyp to develop into a cancer.
What does a bowel polyp look like?
Some polyps are a fleshy nodule on a stalk – these are called pedunculated polyps. Some polyps are flat lesions, barely raised above the surrounding bowel lining – these are called sessile polyps.
Many polyps are quite small, only a few mm in size. Most are less than 1cm however some may be many centimetres wide. The size does not necessarily correlate with the risk of a polyp having already developed into cancer, although it is rare for a polyp less than 1cm to contain cancer.
What are the different sorts of bowel polyps?
There are a number of different types of polyps in the colon.
- Adenomatous polyps
- These are the most common type of polyp and they have the potential to develop into bowel cancer, although most will not. They are classified by their appearance, size and microscopic features. Larger polyps generally carrier a high risk that they may develop into cancer.
- Sessile serrated adenomas
- These are typically very flat polyps that more commonly develop in the right side of the colon (caecum, ascending colon, transverse colon). The can be very difficult to detect and some may develop into cancer.
- Hyperplastic polyps
- These polyps are usually small and found in the lower colon (sigmoid colon and rectum). They do not carry a risk of developing into cancer, except in patients with a rare syndrome of multiple hyperplastic polyps. It is not always possible to distinguish a hyperplastic polyp from other polyps, so they are often removed to allow microscopic evaluation.
- These polyps do not carry a risk of developing into cancer. They generally occur in patients who have had inflammation of the bowel such as with ulcerative colitis or Crohn’s disease.