A colonoscopy is a procedure to examine the colon or large intestine using a long narrow tube called a colonoscope which contains a tiny camera and a light source. Clear, magnified images of the colon are displayed on a monitor for careful examination.

The colon is the last part of the intestine that leads to the rectum and anus. It holds unabsorbed food which is then passed out in the faeces. Bacteria present within the colon helps digest the food releasing gases. The colon produces fatty acids and absorbs liquid minimising the fluid content of stools.

A colonoscopy may be performed to look for benign growths called polyps, cancer, or other abnormalities in the colon. It may be ordered to screen for colon or rectal cancer or when one has signs and symptoms such as:

  • Blood in the stools
  • Bleeding through the rectum
  • Unexplained abdominal pain
  • Persistent change in bowel habits

Before performing a colonoscopy you will need to:

  • Discuss your current medications with your doctor
  • Alter your diet for a few days to make it easier to cleanse your bowel
  • Use a bowel preparation kit that your doctor will recommend
  • Abstain from any food or liquid intake 6 hours prior to the test

Colonoscopy is performed under conscious sedation through an intravenous line to keep you comfortable. You will lie on your left side with your knees raised to your chest. The colonoscope is gently introduced through the anus into the colon. Air is inflated into the colon for easy movement of the instrument and to provide a better view. Once the scope has reached the junction of the colon and small intestine it is gradually withdrawn and the walls of the colon carefully inspected on the monitor. Any colon polyps are removed and tissue samples obtained from suspicious areas using instruments inserted through the colonoscope. These are sent to the laboratory for analysis. Removal of tissue may result in bleeding which can usually be controlled during the procedure.

Immediately following the procedure, you may experience some abdominal cramps, bloating and gas. You will be observed until you recover from sedation and may be given something to drink an hour later. Your diet should be slowly advanced as tolerated. You can usually leave about 4 hours after the procedure. It is important to have someone drive you home due to the sedation. Your symptoms should resolve on their own within a couple of days. Your doctor will discuss the results with you and plan further treatment if necessary.

Colonoscopy is generally a safe procedure but complications such as excessive bleeding or perforation of the colon can occasionally occur.

Other tests that can supplement a colonoscopy include a sigmoidoscopy, CT scan or CT colonography.