Colonoscopy is the endoscopic examination of the colon and the distal part of the small bowel with a flexible tube with camera passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected lesions. Colonoscopy can remove polyps as small as one millimetre or less. 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 required to follow a low fiber or clear-liquid only diet.

Examples of clear fluids are apple juice, chicken and/or beef broth or bouillon, lemon-lime soda, lemonade and water. It is very important that the patient remain hydrated.

Orange juice, prune juice, and milk containing fibre should not be consumed, nor should liquids dyed red, purple, orange..

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 (such as Colonlytely, Bisacodyl, or picoprep) and large quantities of fluid. These cause the bowel to clear and the patient will have diarrhoea this is the normal effect as the bowel needs to be totally clear of matter.

You must be kept nil by mouth that is, told not to eat or drink, for at least 4-6 hours before the procedure. Any heart or blood pressure medication can be taken with a sip of water.

The procedure

During the procedure the patient is given sedation intravenously. The first step is usually a digital rectal examination, to examine the tone of the sphincter and to determine if preparation has been adequate. The endoscope is then passed through the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, the caecum), 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 carbon dioxide to maximize visibility. Biopsies are frequently taken for histology. Suspicious lesions may be cauterized, cut with an electric wire for purposes of biopsy or complete removal called a polypectomy.

On average, the procedure takes 20-30 minutes, depending on the indication and findings. With multiple polypectomies or biopsies, procedure times may be longer. Anatomic considerations may also affect procedure times.

After the procedure, some recovery time is usually allowed to let the sedative wear off. Outpatient recovery time can take an estimate of 30-60 minutes. You will require someone to help you home afterwards. You will not be able to drive or operate any machinery for at least 12 hours. You will need to go home and rest for the remainder of the day.

One very common after effect from the procedure is a bout of flatulence and minor wind pain caused by air insufflation into the colon during the procedure.