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National Bowel Screening Programme

Public Service, Gastroenterology & Hepatology (Liver), Cancer Network Group, Community Health, Oncology


A positive screening test result does not necessarily mean that bowel cancer is present.  

Small amounts of blood in a bowel motion are most commonly caused by polyps, or other minor conditions such as haemorrhoids (piles), which can easily be treated.

A positive test result means that further investigation is required. This will usually be a colonoscopy (an internal examination of the large bowel).

A colonoscopy involves a specially trained doctor or health professional putting a thin tube into your anus (bottom). There is a very small camera on the end of the tube which is used to examine the lining of your bowel, to see if there are any problems.

A colonoscopy can identify whether polyps (growths) or cancers are present.

If any polyps are found, they will generally be removed and sent to the laboratory to check for any cancer cells.

Polyps are not cancers, but may develop into a cancer over a number of years. Removing polyps is usually painless.

  • About seven in 10 people who have a colonoscopy as part of the National Bowel Screening Programme will have polyps, which if removed may prevent cancer developing
  • About seven in 100 people who have a colonoscopy as part of the National Bowel Screening Programme will be found to have cancer and most will require treatment

Colonoscopy is considered a safe procedure with few risks. However, as with most medical procedures, there can sometimes be problems.

There is a very small risk that the colonoscopy procedure itself, or removal of polyps, will cause serious bleeding or damage to your bowel and you may need further treatment.


This page was last updated at 9:53AM on October 4, 2021.