Bowel Screening

The colonoscopy procedure and treatment

During a colonoscopy a thin flexible tube called a colonoscope is passed into the rectum (the back passage) and guided around the large bowel. The front end of the colonoscope carries a small camera with a light attached which allows the specialist to see the inside of the bowel on a television screen.

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Many of the people we interviewed had had a colonoscopy. Different hospitals have different instructions for patients. Some hospitals tell patients to stop drinking (as well as eating) a few hours before the procedure. Other hospitals allow patients to carry on drinking until it is done.

People recalled how a nurse had met them at the hospital, checked their date of birth, took the blood pressure, and made them feel at ease. They were asked to change into a hospital gown, dressing gown and slippers. A doctor explained what would happen and asked them to sign a consent form.

A colonoscopy is usually performed under sedation, but some people may choose not to be sedated.

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Some people who had been sedated during their colonoscopy remembered little about it.

Doctors prefer patients to be lightly, rather than heavily sedated, so that patients can tell the doctor if they notice any pain. This helps to prevent serious complications. 

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One man compared two colonoscopies, one he had had under sedation and the other without sedation. He thought it was better to be sedated: 

Some people felt anxious before the colonoscopy but did not find it as uncomfortable as they expected. This man, who initially felt frightened, said that there was nothing to worry about.

Another man, who chose to have a colonoscopy without sedation, said that the investigation was not a bad experience.

However, a few people did remember having some pain or discomfort, either when the colonoscope moved round a corner in the bowel or when the doctor pumped air into the bowel to see the bowel wall more clearly. One man had a cramping pain at this stage.

Some people were fascinated to see the inside of their bowel on the television screen. Many hadn't expected it to look so bright and clean and pink. However, one woman described the inside of her bowel as 'mostly yellow'. She said that the screen went 'red' when the polyps were removed. Only one man recalled seeing a 'dark thing' which the doctor said was 'a piece of poo'. Some people hadn't wanted to look at the screen, and a few found they couldn't see it from where they were lying in the room.

During the colonoscopy the doctor may remove one or more polyps. Polyps are not cancer, but can sometimes change into cancer over a number of years. Polyps can be removed painlessly using a wire loop passed down the colonoscope tube. The polyp is cauterized. Sometimes a small tissue sample, called a biopsy, is taken. The tissue sample is checked in the laboratory for any abnormal cells that might indicate cancer.

One woman had three small polyps removed but the fourth was too big to remove during the colonoscopy. She had to have an operation (a right hemi-colectomy) at a later date to remove that one (see More treatment needed after an initial colonoscopy).

Although very few people found the colonoscopy painful, some said it was undignified or embarrassing (also see Why some were reluctant or did not take part).

Sometimes screening practitioners have to take special measures because the patient has another medical problem.

Last reviewed May 2016.

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