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What is a colonoscopy


A colonoscopy is a procedure to examine your large bowel (colon). It is carried out with an instrument called a colonoscope. This is a flexible tube about the width of an adult index finger with a light and a camera at its tip. The instrument is passed into the rectum (back passage).


Why is a colonoscopy performed?

A colonoscopy is usually done
  • as part of a routine screening for cancer
  • in patients with known polyps or previous polyp removal
  • before or after some surgeries
  • to evaluate a change in bowel habits or bleeding or
  • to evaluate changes in the lining of the colon known as inflammatory disorders.
What are the benefits of this procedure?
This procedure can help us to identify an abnormality in the colon, including inflammation, ulcers and very small growths (less than 1cm). A biopsy (tissue sample) can be obtained during the investigation to be sent to the pathologist for analysis. Therapeutic intervention (treatment) is possible such as removal of excessive tissue growth (polyps) during the investigation.
What are the risks?
Although complications are rare you should be aware of the following:
  • An abnormality might be missed, perhaps because the bowel was not cleaned adequately or for technical reasons. This happens in about 1 in 20 procedures.
  • Bleeding - this happens in about 1 in every 2,000 procedures and 1 in every 100 procedures when the removal of polyp (polypectomy) is performed. Rarely, significant bleeding may require admission into hospital and a blood transfusion.
  • Perforation - A small hole called a perforation, can he made during the procedure (the risk is approximately 1 in every 500-1000 procedures). If a therapeutic intervention is performed such as a polypectomy, the possibility can be up to 1 in 50-100 procedures.


  • Very frail and/or elderly patients can get pneumonia if stomach juices getting into the lung after having sedation.


  • Reaction to the sedation. This is a rare complication.


Are there any alternatives?


  • A CT scan can be performed but the investigation is less sensitive than a colonoscopy. Inflammatory changes and small lesions (less than 1cm) can be missed.



  • A barium enema can provide x-ray images of the colon but biopsies cannot be performed. This investigation is less sensitive than a colonoscopy.


How do I prepare for the colonoscopic examination?

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