A colonoscopy is performed for both diagnostic and therapeutic reasons, and commonly done with sedation.
Common Reasons for the Test:
- To diagnose lower gastrointestinal (GI) tract disease that causes abdominal pain and/ or bleeding from back passage (rectum)
- To diagnose a tumour in the presence of ‘alarm’ features including a change in bowel habit consisting of diarrhoea (increased bowel frequency or loose stool or both), weight loss or iron deficiency anaemia
- Family history of colon cancer
- Follow up test for abnormal barium enema or CT colonography
- Follow up examination for past history of colon polyp(s)
The alternative tests to examine the colon include a barium enema or CT colonography examination. These have the disadvantage that tissue samples (biopsies) cannot be taken for analysis. If a polyp (a protrusion or growth on the bowel lining) is diagnosed, a colonoscopy would still be needed for polyp removal. They are reasonable alternatives in the case of a failed colonoscopy or patient preference. A medically unfit patient who couldn’t tolerate the conventional laxative bowel preparation may be suitable for a CT with oral contrast (faecal tagging).
Preparing for the Test
Stop Clopidogrel (7 days) or Warfarin (5 days) before the test if instructed, and temporary Heparin injection may be necessary.
1 Week Before Test
48 Hours Before the Test
24 Hours Before the Test
On the Day of Test
In the Endoscopy Room
Drugs Commonly Used for the Test
Injection - Sedatives (benzodiazepine, midazolam)
- Painkiller (morphine, commonly pethidine or fentanyl)
Patient Position(s) During the Test
Left lateral (see picture 1).
Occasionally, you may be asked to change your position to help the endoscope advance. This may involve lying on your back (picture 2).
Can I Watch the Test?
This would be possible as the head position faces the video monitor, and the injection drugs (if given) are aimed at minimal to moderate sedation only.
You won’t feel any pain from having some biopsies taken or polyp removed. Injection of additional sedative or painkiller (morphine) drugs will be given as necessary during the test for adequate control of pain or discomfort.
The complication of perforation (tear of the bowel lining) occurs infrequently, about 1 in 1000 colonoscopy examination. The risk is higher with polyp removal. The risk of bleeding at the site of biopsy or polyp removal is about 1 in 100-200 examinations.
If any of the above complications occur during the test, endoscopic treatment may be applied. In severe cases, surgery may become necessary.
If there is any concern regarding the above complications straight after the test (in recovery), patients will be admitted for close monitoring and/ or treatment.
The main differences between a flexible sigmoidoscopy and a colonoscopy are:
- A flexible sigmoidoscopy test is limited to the left side of the large bowel (colon)
- It is done mostly for diagnostic reason, normally without sedation although this can be given if requested
- It doesn’t normally require oral laxative bowel preparation. A phosphate enema (fluid placed in the rectum) is given to clear the bowel on the day of the test.
Specialist Endoscopies and more . . .