Colonic (Bowel) Polyps

bowel polyps

A colonic (bowel) polyp is a small benign (noncancerous) growth that sometimes forms on the inside lining of the colon or rectum. Some people develop just one colonic polyp, but it is not uncommon to develop two or more. However, it is uncommon to have more than five. A colonic polyp may have a stalk and a head which looks like a small mushroom growing from the lining of the bowel. Some are flatter and just look like a lump on the lining of the bowel.

Most colonic polyps develop in the part of the colon called the descending colon.

Types of colonic polyp

Colonic polyps are generally divided into three types: hyperplastic polyps, adenomas, and polyposis syndromes.

Hyperplastic polyps

These are common. They are usually less than half a centimeter in diameter. They are generally regarded as harmless, perhaps very rarely developing into a cancer.


These too are common. Most are small, usually less than one centimetre in diameter, but sometimes they are bigger. There is a small risk that an adenoma may, in time, become cancerous. If one does turn cancerous, the change usually takes place after a number of years. Most colorectal cancers (bowel cancers) develop from a polyp that has been present for 5-15 years. The exact risk of developing cancer from an adenoma is difficult to be certain of.

Polyposis syndromes

Polyposis syndromes are a group of hereditary conditions. They include: familial adenomatous polyposis (FAP), hereditary nonpolyposis colorectal cancer (HNPCC)/Lynch's syndrome, Gardner syndrome, Turcot's syndrome, Peutz-Jeghers syndrome, Cowden's disease, familial juvenile polyposis, and hyperplastic polyposis. These are rare syndromes, occur in young people, and often cause multiple colonic polyps that have a high chance of developing into bowel cancer.

Who gets bowel polyps and what causes them?

Most colonic polyps develop in older people. About 1 in 4 people over the age of 50 develop at least one colonic polyp. The cause is not clear. The polyp is like a local fleshy overgrowth of tissue that lines the bowel.

What are the symptoms of colonic polyps in older people?

Most people with one or more colonic polyps do not have any symptoms. Occasionally, symptoms may occur. These include: bleeding from the anus, mucus mixed in with faeces, and, rarely, diarrhoea or constipation.

How are colonic polyps diagnosed?


Most colonic polyps are diagnosed by this procedure. Colonoscopy is a test where a doctor looks into your colon. A colonoscope is a thin, flexible, telescope. It is about as thick as a little finger. It is passed through the anus and into the colon. It can be pushed all the way round the colon as far as the caecum (where the small and large intestine meet). The colonoscope contains fibre optic channels which allow light to shine down so the operator can see inside your colon.

Other tests

Sometimes a colonic polyp is diagnosed by other tests such as a barium enema (a special X-ray test of the bowel) or sigmoidoscopy (like colonoscopy, but using a shorter telescope).

How are colonic polyps treated?

If you are diagnosed with a colonic polyp, you will usually be advised to have it removed, even if it is causing no symptoms. This is to prevent the risk of it developing into a cancer at some point in the future.

Most colonic polyps can be removed during a colonoscopy. The colonoscope has a side channel down which grabbing devices can pass. These can be manipulated by the operator. The operator can therefore see and also remove a polyp during a colonoscopy. It is usually painless to have a polyp removed. Once removed, the polyp is sent to the laboratory to be looked at under a microscope. This is done to check that it has been completely removed, to check the type of the polyp, and whether it is benign or showing signs of cancerous change.

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