An endoscopic examination of the large bowel and distal part of the small bowel is performed using a camera incorporated into a flexible tube passed through the anus.

Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a fibre optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis and grants the opportunity for biopsy or removal of suspected lesions.

Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.

A colonoscopy allows an examination of the entire colon (measuring four to five feet in length).


The colon must be free of solid matter for the test to be performed properly. For one to three days, the patient is asked to follow a low fiber diet. On the day before the procedure only clear fluids should be taken. Examples of clear fluids are apple juice, chicken and/or beef broth or bouillon, lemonade, sports drink, and water. It is very important that the patient remains hydrated. Sports drinks contain electrolytes which are depleted during the purging of the bowel. Orange juice and milk containing fiber should not be consumed, nor should liquids coloured red purple, orange, or sometimes brown; however, cola is allowed. In most cases, tea (no milk) or black coffee (no milk) are allowed.  The day before the colonoscopy, the patient is given a laxative preparation in the form of Moviprep to clean the bowel completely.  Since the goal of the preparation is to clear the colon of solid matter, the patient should plan to spend the day at home in comfortable surroundings with ready access to toilet facilities.

The patient may be asked to stop aspirin for up to ten days before the procedure to avoid the risk of bleeding if a polypectomy or biopsy is performed during the procedure.

Before the procedure the patient is normally given sedation intravenously.

The endoscope is passed through the anus into the rectum, the colon (sigmoid, descending, transverse and ascending colon, the ceacum), and ultimately the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximize visibility.  Biopsies are frequently taken for histology.

Suspicious lesions may be cauterized, treated with laser light or cut with an electric wire for purposes of biopsy or complete removal polypectomy. On average, the procedure takes 20–30 minutes, depending on the indication and findings.

After the procedure, some recovery time is usually allowed to let the sedative wear off and to ensure that the patient is eating and drinking without difficulty.  It is advised that you should be accompanied home after the procedure due to the affects of the sedation.

It can be common after the procedure to experience a bout of flatulence and/or minor wind pain caused by air insufflation into the colon during the procedure.

An advantage of colonoscopy over x-ray imaging or other, less invasive tests, is the ability to perform therapeutic interventions during the test. A polyp is a growth of excess of tissue that can develop into cancer. If a polyp is found, for example, it can be removed by one of several techniques. A snare device can be placed around a polyp for removal. Even if the polyp is flat on the surface it can often be removed.


This procedure has a low (0.35%) risk of serious complications.

Nicholas Boyle


Medical Secretary:
Karen Mays

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