Colonoscopy explained

What is a colonoscopy?

A colonoscopy is a test that uses a narrow, flexible camera called a endoscope to look at the lining of your colon.

A colonoscopy is performed to examine the inner surface of the colon to see if there are any abnormalities that may need further investigation.


What is the colonoscopy process like?

A few days before your procedure, your doctor will give you a laxative-type medicine that will clear out your colon. You will also receive a list of foods and drinks you should avoid before the colonoscopy.

Before the procedure, you may be offered a sedative and a painkiller to help you to relax and be as comfortable as possible during the procedure.

During the procedure your doctor will ask you to lie on your side (usually your left side) and bend your knees. They will then perform an internal examination with their finger, and then they will insert the endoscope.

The doctor can then examine the inside of your colon.

In order to make it easier to see, he or she can pump air into your colon through the endoscope to inflate it slightly and give a better view of your colon.

How does colonoscopy work?

Your doctor will gently pass the endoscope through your colon, gently rotating the tip to follow the shape of your colon. A light at the end of the endoscope illuminates the surface of the colon, and the camera transmits the images to a monitor.

Typically, a colonoscopy will take between 30 and 45 minutes to perform. If your doctor feels it is required, they may remove polyps, or perform a biopsy during the procedure.

After the procedure, it will take up to 60 minutes for the effects of the sedative to wear off. You may feel some bloating and discomfort as a result of the air in your colon. You should pass gas and not feel embarrassed doing this either during or after the procedure. This will relieve your feelings of bloating and cramping.

You may feel groggy after the sedative, so you should not drive yourself home.

Why is colon cleansing important?

Before a colonoscopy, it is very important that your colon is completely cleaned out, so that the doctor can examine it all.

If your colon is not completely clean, it increases the chance that your doctor will miss abnormalities, and increases the likelihood that the procedure will have to be repeated at a later date.

There are three main kinds of laxative-type medicines, called bowel preparations, available to cleanse your colon:

  • Polyethylene glycol-based bowel preparations (also known as PEG-based)
  • Sodium picosulfate bowel preparations
  • Trisulfate bowel preparations

Your doctor will prescribe the bowel preparation they think is most suitable for you based on how much you can drink and its type.

When cleansing your bowel you must drink all of the bowel preparation, plus extra fluids to stay hydrated. The total amount you need to drink varies between bowel preparations, with the lowest being 2L and the highest being 4L.

A guide to successfully taking your bowel preparation


What if you are taking medicines?

You can take most medicines right up to the day of the colonoscopy. Any medicines you take by mouth may not be absorbed in the usual way when taken within 1 hour of drinking your bowel preparation before the colonoscopy. You should tell your doctor about medications you are taking, particularly aspirin products, arthritis medications, anticoagulants (blood thinners such as warfarin or heparin), clopidogrel, insulin or iron products. Also, be sure to mention allergies you have to medication.