What is Colonoscopy?

Colonoscopy is a test which allows the endoscopist to directly examine the lining of the large intestine (the colon). Diagnostic colonoscopy is recommended for persistent change in bowel habit, occult or frank blood in the stool, unexplained anaemia and as a screening test for colon cancer. In order to do the test a colonoscope is carefully passed through the anus into the rectum and advanced through the intestine. The colonoscopy is a long flexible tube, about the thickness of your index finger, with a bright light and video camera at its tip. The video camera on the colonoscope transmits images of the inside of the colon to a monitor, allowing the endoscopist to examine the lining of the colon for any disease or abnormalities.

What else may be done during the procedure?

During the colonoscopy a biopsy (a sample of the lining of the bowel for closer examination under the microscope) may be taken using tiny biopsy forceps passed through the colonoscope. This is a painless procedure.

It is also possible to remove polyps during a colonoscopy. Polyps are abnormal projections or growths of tissue from the lining of the bowel, rather like a wart, and certain types of bowel polyps may be at risk of developing into cancer if left. If polyps are found the endoscopist may decide to remove them via polypectomy during the procedure; again this is a painless procedure. Occasionally it may be necessary to return for a repeat colonoscopy in order to treat large or difficult to remove polyps.

Bowel preparation

To allow a clear view, the colon must be clean and completely empty of waste material. If it is not, certain areas may be obscured and the test may have to be abandoned and repeated at a later date.

It is important to take all of the laxatives prescribed and considerably increase your intake of clear fluids on the day before the examination, which will help clean the bowel. Please also follow the dietary instructions for the few days preceding the test, as this will also help to ensure the bowel is clean for the test. You will be sent detailed information and instructions on how to take the laxatives in the post.

When you come to the department, a member of staff will explain the test to you and ask you to sign a consent form. This is to ensure that you understand the test and any potential complications that may occur. Please tell the doctor of nurse if you have had any allergies or bad reactions to drugs or other tests in the past. They will also want to know about any previous endoscopy you have had, or any other medical conditions which you may suffer from and details of medication which you may be taking. If you have any worries or questions at this stage don’t be afraid to ask, the staff will want you to be as relaxed as possible for the test and will not mind answering your queries.

During the procedure

You will be placed in a comfortable position on your left side, and may be given medication by injection through a vein to make you sleepy and relaxed. The endoscopist will then pass the colonoscope into the rectum, and advance it through the colon. Colonoscopy is not usually painful. You may experience some abdominal cramping and pressure from the air which is introduced into your bowel; this is normal and will pass quickly. You may also be asked to change position during the examination, and will be assisted by a nurse. The examination usually takes anywhere from 15-60 minutes.

After the procedure 

You will be left to rest in the recovery area for up to 1 hour, until the main effects of any medication wear off. A responsible adult must be available to escort you home as the sedation impairs your reflexes and judgement. For the remainder of the day you should not drive a vehicle, operate machinery or make important decisions. We suggest that you rest quietly.

When will I know the results?

In most cases a member of staff will be able to tell you the results of the test as soon as you are awake and you will given a copy of the endoscopy report to take home. However, if a biopsy sample or polyp was removed for microscopic examination these results may take up to two weeks to process.

Many patients find that sedation tends to make them forget any explanations that may have been given to them after the procedure. Details of any results or further investigations may be obtained from your GP or specialist (whoever referred you for the test), and will usually be detailed on your copy of the endoscopy report.

What to expect after a Colonoscopy

After your colonoscopy a responsible adult must collect you, as you will be drowsy from the medication you have been given. You must not drive a vehicle, drink alcohol or make any important decisions until the day following your discharge. This is because it takes some time for the medication to work its way through your system. You may resume your normal daily activities the day after the examination. 

The doctor or nurse will have told you before being discharged if you had biopsies taken or polyps removed. If this was the case you may notice traces of blood coming from your back passage. If bleeding persists, becomes more severe or the abdominal pain becomes worse, you should contact either the Endoscopy Unit, your GP or go to your nearest Accident & Emergency Department (taking the copy of your endoscopy report with you).

Food and drink

Alcohol in combination with any sedation you may have received is likely to make you much more sleepy than usual. Normal food can be taken after the examination, though you may prefer light meals on the day of the examination.


You may resume normal medications immediately after your colonoscopy but if a polyp was removed we may advise against taking certain blood-thinning or anti-inflammatory drugs for a defined period. Please ask if you are not sure that a medication will be safe. You may take stool softeners and bran but do not take strong laxatives.

Bowel actions

Your colon has been completely emptied and you should not expect necessarily to start to have normal bowel function for two to three days. Bowel actions after that should rapidly return to normal.

Things to report to your doctor

  • Severe pain or vomiting
  • Passage or vomiting of blood
  • Temperature greater than 38 degrees
  • Redness, tenderness and swelling at the site of the intravenous injection that persists

If you have any worries please do not hesitate to contact either the Endoscopy Department, your own GP or go to the Accident & Emergency Department of your local hospital (taking the copy of your endoscopy report with you).