What is a colonoscopy?

A colonoscopy is a procedure used to see inside the rectum, colon and terminal ileum (small bowel). Colonoscopy can detect inflamed tissue, ulcers, and abnormal growths. The procedure is used to look for early signs of colorectal cancer and can help doctors diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the anus, and weight loss.

The colon and rectum are the two main parts of the large intestine. The colon is the most distal portion of the intestine, also known as the large intestine. It takes in small bowel effluent, absorbs water, solidifies the stool and disposes of the waste through the act of defecation. The colon is attached to the anus via the rectum.

When is a colonoscopy done?

A colonoscopy is recommended in the following situations:

How do you prepare for a colonoscopy?

You will be given written instructions on how to prepare for a colonoscopy. The process is called bowel preperation. Generally, all solids must be emptied from the gastrointestinal tract by following a clear liquid diet for the day preceding the procedure. Acceptable liquids include:

A laxative will be required the night before colonoscopy. A laxative is a medicine that loosens stool and increases bowel movements. Laxatives are usually ingested as a powder dissolved in water. Patients should inform the surgeon of all medical conditions and any medications, vitamins, or supplements taken regularly, including:

Driving is not permitted for 24 hours after colonoscopy to allow the sedative time to wear off. Before the appointment, patients should arrange to be collected after the procedure.

How is a colonoscopy done?

Once intravenous access is obtained, a trained sedationist or anaesthetist will administer conscious sedation. This is not a full anaesthetic, but you will not experience any discomfort or have any recollection of the procedure. The surgeon will ask you to lie on your left side. Once sedated, Dr Cooper will insufflate your colon with air and then pass a thin tube that has a fibre-optic light source with a camera at the tip, from the anus to the start of the colon (caecum) or the small bowel (ileum) in a controlled manner. The procedure takes 20-25 minutes to complete.

Removal of polyps and biopsy

The endoscopist can remove growths, called polyps, during colonoscopy, which will then be tested in a laboratory for signs of cancer. Polyps are common in adults and are usually harmless. However, most colorectal cancer begins as a polyp, so removing polyps early is an effective way to prevent cancer.

The endoscopist can also take samples from abnormal-looking tissues during colonoscopy. The procedure, called a biopsy, allows for the tissue to be tested for signs of disease.

The endoscopist removes polyps and takes biopsies using tiny tools passed through the scope. If bleeding occurs, he/she can usually stop it with an electrical probe or special injections passed through the scope. Tissue removal and treatments to stop bleeding are usually painless.


A colonoscopy usually takes 20 - 25 minutes. Cramping or bloating may occur during the first hour after the procedure. The sedative takes time to completely wear off. Patients may need to remain at the hospital for 1 to 2 hours after the procedure. Full recovery is expected by the next day. Discharge instructions should be carefully read and followed.


The most feared complication of colonoscopy is perforation. Fortunately this occurs very infrequently with a rate of 1 per 1000 cases being deemed acceptable for screening colonoscopies. The perforation rate, unfortunately, increases 7 fold if a polyp has been removed. Other complications include haemorrhage and transient bacteraemia (blood infection).

Patients who develop any of these rare side effects should contact their doctor immediately: