Colonoscopy

A colonoscopy uses a thin, flexible tube with a light and a camera to look at the inside of the whole large bowel, the colon and rectum. Small growths called polyps can be removed, and samples (biopsies) taken, during the test.

A doctor may suggest it to find the cause of blood in the stool, bowel habits that change and do not settle, tummy pain, weight loss or anaemia. It is also used to check for polyps, bowel cancer, Crohn's disease and ulcerative colitis, and to screen for bowel cancer in people with no symptoms.

Bowel preparation is the main task, because stool left in the bowel can hide a problem. You will be given a special diet, strong laxatives and a time to stop eating and drinking. Expect diarrhoea and stay near a toilet.

1. You change into a gown. You may be offered sedation, painkillers or gas and air.
2. You lie on your side with your knees drawn up.
3. The doctor passes the thin tube through your back passage along the whole large bowel. You may feel pressure or cramps.
4. Air, carbon dioxide or water is put in to open the bowel, which can make you feel bloated.
5. The doctor checks the lining on the way in and again as the tube is pulled back. Polyps can be removed and samples taken. You will not feel this.

It may be uncomfortable but should not be painful, and it usually takes under an hour. With sedation you will probably not remember it.

You rest in a recovery room for an hour or so. Cramps, bloating and passing wind are common for a few hours, and a little blood from the bottom for a day or two after polyp removal or a biopsy. After sedation, someone must take you home, and for 24 hours you must not drive, drink alcohol or sign important papers.

Get emergency care for heavy or worsening bleeding, severe and worsening tummy pain, chest pain, or being sick again and again. Bleeding can sometimes start up to two weeks after the test. For a fever, contact the hospital urgently.

Serious problems are rare. They include bleeding, mostly from where a polyp was removed or a sample taken, a tear (perforation) in the bowel wall, which may need surgery, and a reaction to the sedative, with breathing problems or low blood pressure. Infection is very rare. Older age and polyp removal make bleeding and tears more likely.

You may be told what was seen once you are awake enough. A letter or call usually follows within a few weeks; if you have heard nothing after 3 weeks, call the hospital. Polyps and samples go to a laboratory, and the report says whether you need more treatment or a repeat check.

A normal result shows no polyps or signs of cancer. The test may also find piles, diverticular disease, Crohn's disease, ulcerative colitis or bowel cancer, and the team will explain what comes next. What it cannot show: stool left behind can hide a problem, and it does not look at the upper digestive tract, which an endoscopy does.