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Colonoscopy is a type of endoscopy that allows a medical practitioner to examine the colon (large intestine (large bowel) and the distal part of the small bowel). A colonoscope is a long thin and flexible tube equipped with a small camera and light and some surgical tools.

It is inserted into the body via the anus and an image of the bowel wall appears on a television monitor so that he medical specialist can diagnose any bowel condition and - in some cases - carry out small procedures, such as taking tissue samples (biopsies) or removing polyps.

As a colonoscopy does not require conventional surgery, there are no incisions in the skin and the procedure is generally painless. This places less stress on the body and consequently the procedure is much quicker, and recovery time is much faster than with conventional surgery. There is also of course no surgical scarring.


A colonoscopy is generally recommended in the following circumstances:

  • Where there is or has been bleeding from the anus / rectum.
  • Where a Faecal Occult Blood Test (FOBT) – a test which monitors blood in faeces (which is invisible to the naked eye) results in a positive reading.
  • Where the patient shows signs of anaemia (deficiency of quality or number of red blood cells in the body).
  • Where there is (unexplained) abdominal pain and altered bowel habit.
  • Where the patient shows (unexplained) weight loss.
  • Where confirmation of possible inflammatory bowel disease (IBD) is required.
  • Where cancer of the bowel runs in the family of the patient.
  • Where the patient has had (cancerous or precancerous) polyps removed previously.

Please speak with your GP or request an appointment if any one or more of these indications fit your symptoms.

Tests other than colonoscopy

A colonoscopy is one of the most comprehensive methods to evaluate abnormalities within the bowel, including inflammation (IBS, IBD), bleeding, polyps and cancer. Alternatively there are other tests available to answer investigative questions around the colon. These procedures are sometimes used in conjunction with a colonoscopy.

  • CT Colonography - also known as virtual colonoscopy uses low dose radiation CT scanning. During this procedure the colon is inflated with gas via a small tube entering the rectum. Subsequently pictures are taken of the digestive tract. This procedure can be used if the colonoscopy was incomplete. 
  • CT Scan - This test is less sensitive to discover abnormalities within the colon compared to a colonoscopy, but it looks at additional structures surrounding the colon.
  • Sigmoidoscopy - A similar procedure to a colonoscopy with the difference that the sigmoidoscope is shorter and is only able to investigate up to the sigmoid colon, the section of the colon directly past the rectum.

Polyps and bowel cancer

Colonic polyps (colorectal polyps) are growths on the lining of the colon and rectum, which can be sometimes cancerous or may grow to become cancerous. Polyps do form from mutated cells lining the colon and these growths are usually harmless (benign). The appearance of these growths in the colon can be sponge like (sessile), look like they are on a stalk like a mushroom or cherry (pedunculated), or they are flat. Some of these initially benign polyps can become cancerous (malignant) and can develop into a cancerous tumor. Colon cancer is one of the most common cancers diagnosed in men and women. Polyps found during a colonoscopy are in most cases resected completely and a thorough evaluation by a pathologist will give the answer if they are malignant or benign. In some cases, resection via endoscopy is not feasible and surgical resection by a specialist surgeon will be recommended.

For more information on bowel cancer read on following website from the Department of Health & Human Services, Bowel Cancer Australia or Gastroenterological Society of Australia.

Complications of colonoscopy

Common risks and complications include:

  • Mild pain and discomfort in the abdomen for one to five days after the procedure.  This usually settles with walking and moving around to get rid of the trapped air.
  • Nausea and vomiting.
  • Faintness or dizziness, especially when you start to move around.
  • Headache.
  • Pain, redness or bruising at the sedation injection site (usually in the hand or arm).
  • Muscle aches and pains.
  • Allergy to medications given at time of the procedure.

Uncommon risks and complications include:

  • Hole (perforation) to the bowel causing leakage of bowel contents into the abdomen. Surgery may be needed to repair the hole.
  • A significant bleed from the bowel where a polyp was removed. Further endoscopy, a blood transfusion or an operation may be necessary.
  • Not being able to see the entire bowel. This can happen if your bowel is not completely clean or the colonoscope could not be passed to the end of your large bowel.
  • Missed polyps, growths or bowel disease.
  • Heart and lung problems such as heart attack or vomit in the lungs causing pneumonia. Emergency treatment may be necessary.
  • Change of anaesthetic from a sedation anaesthetic to a general anaesthetic.
  • ‘Dead arm’ type feeling in any nerve due to positioning with the procedure (usually temporary).
  • An existing medical condition that you may already have getting worse.

Rare risks and complications include:

  • Bacteraemia (infection in the blood). This will need antibiotics.
  • Stroke resulting in brain damage.
  • Anaphylaxis (severe allergy) to medication given at the time of procedure.
  • A tear in the spleen capsule or ligaments.

Preoperative Instructions

The bowel must be empty for the colonoscopy procedure. Special medication is available to help clear the bowels, which needs to be taken the day before the procedure. No food or liquid should be consumed in the 6 hours before the colonoscopy.


A mild anaesthetic is administered before the colonoscopy procedure begins. The procedure itself generally takes no longer than half an hour. As the patient has been sedated, they are kept under observation for 1-2 hours afterwards, after which they may return home.

Postoperative Instructions

Because of the effect of the sedation, you must not drive home after the procedure, make important decisions or sign any legal documents in the following 24 hours. You should therefore make alternative transport arrangements. Return to work on the day of the procedure is not recommended.