A colonoscopy is an examination of the colon performed under anaesthesia. A flexible instrument carrying a video camera is inserted through the anus and passes around the bowel. It is an excellent tool to diagnose a range of bowel problems. In particular, it is used to identify the presence of cancer or to remove polyps from the bowel before they have a chance to develop into cancer. Polyps are small benign growths that grow on the wall of the colon. They occur in about 10% of people and generally have no symptoms. A small proportion of them will eventually turn into bowel cancer. People with a strong family history of bowel cancer and those who have had previous colonic polyps removed are at higher risk of developing polyps and bowel cancer. A colonoscopy currently gives the best view of the entire colon and rectum. It also allows biopsies to be taken and polyps removed.

Before a colonoscopy is performed, the bowel needs to be cleaned out. This is referred to as a “bowel preparation” and it usually involves the ingestion of an oral preparation on the day before the procedure that induces a form of diarrhoea to remove all the bowel content.

The colonoscopy procedure is usually performed under general anaesthetic and requires admission to hospital for several hours.

The major risk associated with a colonoscopy is perforation of the colon. This is reported to occur in about one case in every 1,000 colonoscopies in Australia. Its occurrence is related to technical factors in the colon and the experience of the colonoscopist.   It can be a serious problem that can be treated with or without surgery, depending on the circumstances. The other significant risk associated with colonoscopy is bleeding, which may follow the removal of a polyp in about one in a hundred cases.  Bleeding is rarely serious and will usually stop spontaneously. Very uncommonly a blood transfusion may be required and, more rarely, a colonoscopy or even surgery to stop the bleeding.

Your doctor will discuss the full details of the colonoscopy procedure and the risks involved at the time of your consultation.

Screening Colonoscopy

Screening colonoscopy is designed to prevent bowel cancer. It is known that one in seventeen males and one in twenty-four females will develop bowel cancer in our community. The evidence shows that colonoscopy screening reduces that figure by detecting and removing the polyps before they develop into cancer.

Some currently recommended screening colonoscopy regimes:

1.   Low risk group

No family history of colorectal cancer or one first degree relative over the age of 55

Recommended screening colonoscopy:

2.   Moderate risk group

Two first degree relatives on the same side of family or one first degree
relative under the age of 55.

Recommended screening colonoscopy:

3.   High risk group

HNPCC (Hereditary Non-Polyposis Colorectal Cancer)
Colonoscopy 2 yearly from age 25 or 5 years younger than the index case

FAP (Familial Adenomatous Polyposis)
Annual flexible sigmoidoscopy from age 15

Colonoscopy every 3 years if the polyp is:
Larger than 1cm, villous, with high grade dysplasia or more than 2 polyps present
Otherwise, colonoscopy every 4-6 years

Personal history of colorectal cancer
Colonoscopy every 3 years

Click here to view images of bowel polyps. These images are quite confronting and not for the faint hearted.