Colonoscopy is a procedure where an instrument is used to examine the inside or lining of the colon. A colonoscope is a long, flexible fibre-optic instrument with a light source and camera at its tip. It is passed through the anus and guided around the colon. The procedure is performed in a day surgery unit under sedation or sometimes, full general anaesthesia. On the days prior to the colonoscopy the bowel must be prepared so it is necessary to have a clear liquid diet and to drink a laxative solution. This solution will produce dramatic diarrhoea and thereby empty out the bowel.
During the procedure, the lining of the bowel is closely inspected. Any abnormalities can be photographed, biopsied if appropriate and some lesions, such as polyps, can often be completely removed.
Like any procedure, colonoscopy is accompanied by some risks and side effects – but overall these are uncommon. They can be associated with the preparation, including nausea and vomiting, and sometimes a headache or dizziness related to dehydration. There can also be side effects from the anaesthetic or medications used for sedation.
If polyps are removed or biopsies are taken there is a small chance of bleeding which can occur 1-2 weeks after the procedure. The most serious risk is perforation of the colon. This usually requires hospitalisation, antibiotic treatment and possible bowel surgery.
Patients with a family history of bowel cancer, or a personal history of inflammatory bowel disease or polyps, may require regular screening with colonoscopy. Any patient with symptoms such as a persisting alteration in bowel function or rectal bleeding should be seen by a doctor to assess the need for colonoscopy.
Virtual Colonoscopy – CT Colonography
This can be an alternative to colonoscopy in situations where colonoscopy may be too risky or otherwise inappropriate.
As with normal colonoscopy, a bowel preparation is needed although this is often not as aggressive as before a colonoscopy. A fine catheter is then inserted into the anus and the colon distended with carbon dioxide. A CT scan is then performed with the patient lying both on their back and on their abdomen. These two sets of scans are then combined to make a composite image of the lumen of the bowel.
Although a good diagnostic test, unfortunately therapeutic interventions cannot be performed as a part of this procedure and abnormal findings need to be appropriately followed up.