Colonoscopy is the examination of the large bowel (colon) and the end of the small bowel using an instrument passed through the anus. The instrument is called a colonoscope. It may have a small camera attached for visualization and for keeping as a record.
The bowel needs to be cleaned out prior to the test. A powerful laxative is given the night before.
A light anaesthetic is administered as the procedure, which previously was performed without anaesthetic is quite uncomfortable.
The gastro-enterologist doing the colonoscopy will remove any small suspicious lesions such as polyps found during the test.
Recent studies show that flat lesions, not just polyps should be looked for and biopsied. It seems that flat lesions are more likely to become cancerous over time.
Flat lesions are identified by spraying an indigo dye on the bowel wall: flat lesions pick up the dye more than normal tissue.
When you are scheduled for a colonoscopy, either routine or as a part of a work-up, ask your doctor if the flat-lesion dye test is included.
People with familial polyposis, a genetic tendency to produce bowel polyps, are at high risk for developing cancer in these polyps. Frequent -annual or even more frequent - colonoscopy is recommended. In their case polyps are more dangerous.
Many peolpe with familial polyposis will have the colon removed as a precaution against developing cancer.
Virtual colonoscopy uses CAT or MR scanning to visualize the bowel. It has the advantage of not needing an anaesthetic. However it has the disadvantage of possibly missing very small lesions. And if an abnormality is found than a colonoscopy will be needed anyway. Virtual colonoscopy is more expensive and if done by CAT exposes the patient to radiation.
Colonoscopy has risks although they are rare. The bowel may be perforated which requires immediate emergency surgery to prevent infection which could be life threatening. Any anaesthetic carries a small risk.
