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.

  1. 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.
  2. 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.
  3. 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.
  4. Inflammatory
    • 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.

Small colonic polyp – Tubular Adenoma
Large colonic polyp – Tubular Adenoma
Flat Polyp – Sessile Serrated Adenoma

How are polyps removed?

The medical term for the removal of a polyp is polypectomy. This is performed during a colonoscopy.
Small polyps can be removed with wire snare or loop that is inserted down the colonoscope, over the top of the polyp and then closes, snipping off a small pieces of tissue. Larger polyps may require additional techniques to aid complete removal of the polyp. This could include injecting a solution under the polyp, using cautery or electrical current to help burn off the tissue (and to reduce the risk of bleeding), applying clips or loops to reduce the blood supply to a polyp before it is removed or to minimise the risk of complications.
Polypectomy is not painful because the bowel lining does not have the ability to feel pain. Polypectomy is generally safe however there are a few potential risks. Bleeding can occur at the time a polyp is removed, and can usually be controlled with cautery (applying heat) or applying metal clips to the bleeding point. Rarely, delayed bleeding can occur up to 7 days after the polypectomy. There is also a risk of perforation, where a hole forms in the bowel wall. Sometimes surgery is required to treat perforation. If you experience significant bleeding from the bowel or new abdominal discomfort after the procedure, you should seek medical attention.

What happens after the polyp is removed?

The polyp tissue will be sent to a pathology laboratory and examined under a microscope. This will determine what type of polyp it is and whether there are any worrying features. Occasionally, cancer is found within a polyp and surgery may be then required.
Depending on the size, type and number of polyps removed, your doctor will advise you on the necessity and timing of future colonoscopies: this is usually in 3 to 5 years. Sometimes the interval is shorter if your doctor needs to check a polyp was completely removed, if the bowel preparation was suboptimal if you had a large number of polyps or you have a very strong family history of bowel cancer.