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Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 3 minutes read

A colonoscopy is a procedure using a camera to check the inside of your bowel, with the aim of looking for any signs that are causing your symptoms.

A colonoscope is a thin, flexible tube, the size of a pen, that is passed into your back passage. It has a camera on the end to view different parts of your bowels, and it may take some photos for future reference. It's usually done in a hospital by a gastroenterologist or colorectal surgeon.

In order to get a good view, it’s essential your bowel is cleared out beforehand, and they may blow a little gas in to see the bowel lining fully. It just views the rectum and large bowel (the colon), not the small bowel (intestines).

Why do I need a colonoscopy?

Your doctor may have referred you to investigate symptoms, such as a persistent change in bowel habits (diarrhoea or constipation), abdominal pain or bleeding from the back passage. Other reasons for a colonoscopy are unexplained weight loss, reduced appetite or fatigue, and iron deficiency anaemia with no obvious cause. Your GP may have found a lump on examining your abdomen that requires a colonoscopy.

These can represent conditions such as inflammatory bowel disease (either Crohn’s disease or ulcerative colitis), diverticular disease or bowel cancer.

What might the doctor find on a colonoscopy?

Tiny growths called polyps are one possible finding in your bowel – these are usually harmless but the doctor will take a tissue sample in case they indicate something more serious.

The doctor will look for any abnormalities in the bowel wall that could indicate disease, and any changes to the structure that could be causing a blockage. Inflammatory bowel conditions, diverticular disease and bowel cancer all have distinct appearances on colonoscopy. They will take tissue biopsies of any unusual areas to determine the exact cause and analyse it under the microscope.

It's also common for the doctor not to find anything concerning during the procedure.

How do I prepare for a colonoscopy?

You’ll receive a letter in advance of the procedure to tell you how to prepare. The advice is usually that two days prior to the colonoscopy, your diet should switch to more bland foods, without sauce and spices.

The day before you’ll be asked to take strong laxatives to clear out your bowels, so they can get a clear view with the camera. It’s best to stay close to the toilet to prevent any unfortunate accidents.

On the day of your procedure, you will be advised when to stop eating and drinking. The actual procedure should take around 30 to 45 minutes, but you should allow at least half a day for everything, and you may feel a bit drowsy afterwards – someone else should drive you home. You should receive your results after 2 to 3 weeks, once any tissue samples have been processed.

Will I be put to sleep for this procedure?

You are usually awake during the procedure, unless there is a specific reason for you to be given a general anaesthetic. To help you relax, you may be offered a sedative medication through a vein or gas and air to breathe in.

You will be offered painkillers, too, although the procedure is described as a bit uncomfortable, rather than painful. Most people tolerate it fairly well, and the doctor carrying out the procedure will be experienced at the procedure and aim to put you at ease. You might feel a bit self-conscious, as staff will be assisting the doctor during the procedure, but rest assured that the team is very used to doing this procedure and keeping you comfortable.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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