Bowel (Colonic) Polyps - Diagnosis

How are bowel polyps diagnosed?

Most bowel (colonic) polyps do not cause symptoms. So, most people with bowel polyps will not be diagnosed. Tests may be done if you have symptoms that indicate a bowel problem, or for various other reasons. For example, if you have seen blood in your stools (faeces) or if you are found to have blood in your stools following a routine screening test which is now offered to older people.

See separate leaflet called Faecal Occult Blood Test for more details.

What is a colonoscopy?

Most bowel polyps are diagnosed by this procedure. Colonoscopy is a test where an operator - a doctor or a nurse - 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 around 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.

See separate leaflet called Colonoscopy for more details.

A sample (biopsy) will be taken at the time of the colonoscopy. This is very important so that it can be checked whether the polyp is cancerous (malignant).

What about other tests?

Sometimes a bowel polyp is diagnosed by other tests:

  • A special X-ray test of the bowel - this procedure is called a barium enema.
  • A test procedure called sigmoidoscopy - this enables a doctor or nurse to use an instrument called a sigmoidoscope to look into the rectum and sigmoid colon. The procedure is similar to a colonoscopy but it uses a shorter telescope.

If a polyp is seen on a barium enema you will still need a colonoscopy to remove the polyp and to take a sample (biopsy) of it for further investigation.

You will also need a colonoscopy if a polyp is found when you have a sigmoidoscopy. This is to make sure there are no more polyps beyond the reach of sigmoidoscopy.

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Dr Colin Tidy
Peer Reviewer:
Dr Adrian Bonsall
Document ID:
13486 (v4)
Last Checked:
02 November 2016
Next Review:
02 November 2019

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.