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 for the diagnosis of 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 to be removed.

A careful and meticulous examination during colonoscopy is essential so that important pathologies such as a cancers and polyps are not missed during the examination.

In addition to making the diagnosis of cancer, it is also very important to know the location of the cancer. Incorrect determination of the cancer's location can lead to the removal of the wrong segment of bowel or lead to a last minute change of plan during the operation. This change of plan may lead to the removal of more bowel than planned and may also prolong the operation time. Nowadays, the location of tumour can be marked with SPOT ink at the time of colonoscopy.

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

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. In expert hands, this can be reduced down to 1:5000 or less. Its occurrence is related to technical factors in the colon and the experience of the colonoscopist. Perforation of the bowel 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 may be required 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.