Colonoscopy
Colonoscopy is a modern electronic video method of examining the entire large
bowel (colon). It is performed under light anaesthesia which results in a
painless procedure during which the patient is lightly sleeping. Its main
advantage over older diagnostic methods is in the detection and removal of
pre-cancerous colonic polyps, the early diagnosis of bowel cancer and a much
more accurate method of assessing the extent and degree of inflammatory bowel
diseases (ulcerative colitis and Crohn's disease). Most or all bowel cancers
are preceded by the appearance of a polyp, which is identified and removed at
the time of colonoscopy. Removal of such polyps prevents the subsequent
development of bowel cancer.
If there is a family history of bowel cancer or pre-cancerous polyps,
colonoscopy may be required as a preventative measure. For example, the
overall risk of contracting bowel cancer at some stage in one's life, usually
(but not always) after the age of 50, is one in 20-25, ie 4%-5% of the population
will develop bowel cancer. If there has been a close relative (parent or
sibling) with bowel cancer or certain types of colon polyps, the risk of
eventually developing bowel cancer is increased to about 1 in 8. This risk
can be reduced to almost zero with colonoscopic surveillance aimed at detecting
and removing any pre-cancerous polyps.
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sessile 1.5cm adenomatous polyp
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The polyp is grasped and tented, ready for excision with electrocautery.
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Previously we have had to rely on barium enema x-rays, but these are less
accurate and there is a greater risk of overlooking polyps or early cancers.
Even if polyps are seen on such x-rays, colonoscopy is required for their
removal. Unlike a barium enema x-ray, modern colonoscopy involves no
irradiation nor discomfort. Advantages of barium enema x-ray include wider
availability, cheaper cost, and intravenous sedation in a hospital setting is
not required.
Colonoscopy involves less than half a day in hospital. Before colonoscopy
(usually the evening before, at home) a laxative mixture will be required to
cleanse the bowel. Other than removal of polyps (polypectomy), minor surgical
procedures for conditions such as haemorrhoids can be performed.
Serious complications, such as prolonged bleeding or bowel perforation following removal of a polyp, are fortunately rare, and in this practice occur in one per 1000 - 2000 colonoscopies. These cases are managed immediatley in hospital, and corrective surgery is required in only a small minority.
