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A closer look at: colonoscopy

If you have symptoms such as persistent diarrhoea or a change in your bowel habits, or bleeding or mucus coming from your back passage, your doctor may recommend a test called a colonoscopy. A colonoscopy allows a closer look inside your large intestine (rectum and colon) to find out what is causing your symptoms.

Colonoscopy is the examination of the bowel with a flexible video ‘telescope’. It is carried out to investigate bleeding from the rectum (back passage), changes in bowel movements, abdominal pain and other abnormalities, to check for disease and to look for polyps (small growths on the wall of the bowel).


Before the examination

  • You will be given laxatives to take at set times on the day before the examination, and you should drink only clear fluids (water, black tea or coffee, or squash) to help clean the bowel and avoid dehydration.
  • It is important that the bowel is clean and empty before a colonoscopy. If the bowel is not properly prepared it can be difficult to see the bowel lining clearly and problems may be missed, so follow instructions carefully. If the findings are unclear, the procedure may have to be repeated.
  • You will have the option of sedation, given as an injection or gas and air, or you can choose to remain unsedated. If you have a sedative you will feel drowsy but remain conscious. You may feel drowsy and/or unsteady for up to 24 hours, so it is important to have someone to help you home after the procedure, and you should not drive or carry out any activity that could be compromised by a lack of attention.

The procedure

For the colonoscopy, you will be asked to lie on your side with your legs drawn up toward your chest. You may be asked to change position during the procedure; the endoscopist and nurse will help you.

Colonoscopy position

  • The tube is passed into the bowel through your rectum. Some air will be blown into the bowel to improve the view of the bowel wall. This can make you want to pass wind, and you will be encouraged to do so to reduce any discomfort. Doctors and nurses are used to this, so don’t worry.
  • The examination is usually performed as an outpatient procedure, and typically lasts 15–30 minutes.
  • Occasionally, small pieces of tissue may be removed painlessly (biopsy) by the colonoscope for more detailed examination in the laboratory. Results are usually available in 1–2 weeks. Polyps can also be removed using this procedure.

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Last updated: Thursday, March 17th 2016


Anal bleeding should always be checked out by your doctor. Find out more from Dr Phil Hammond:

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Comments on this article

Posted by Jocelyn on 26/11/2018 at 03:33

My husband recently found out he's due for a colonoscopy, and I wanted to learn more about this procedure so I'll know what he's going through. Your article had just the advice I was looking for, and I liked how you said its important that its important to follow instructions carefully before the procedure, as the bowels must be completely emptied before examination or it may have to be repeated. Thanks; I'll share this with my husband and hopefully this information will help him with his upcoming colonoscopy.

Posted by Optional on 13/02/2018 at 10:14

Been constipated bout 2 months now and been trying laxatives but I have one big pile around my anus and this make pushing when pooping difficult for me it burns me and the pain is horrible so I tried to poop what I can and always left the big poop in my belly,this make me stress and feel bad, please any help

Posted by Optional on 29/08/2016 at 05:58

I am severely constipated. I have talked to my doctor and I have had all the normal tests and I am taking stool softener plus fiber supplements. I am still having trouble passing stools and I seem unable to push. Is there a physical reason why my spincter isn't working properly, how do I determine that and fix it ?


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