Colonoscopy Information

This section of the website details what a colonoscopy is, and provides information for patients preparing for the procedure.

What is a colonoscopy?

Colonoscopy lets the endoscopist look inside your entire large intestine, from the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. The procedure is used to diagnose the causes of unexplained changes in bowel habits. It is also used to look for early signs of cancer in the colon and rectum. Colonoscopy enables the endoscopist to see inflamed tissue, abnormal growths, ulcers, bleeding, and muscle spasms.

During the procedure the endoscopist may take a small tissue sample to be analysed under a microscope, this is called a biopsy. Polyps may also be seen. Polyps are abnormal projections of tissue, rather like warts, it is possible to remove them during the procedure, this is quite painless.

You will be required to remove your clothing and put on a hospital gown. The colonoscopy will be performed with you lying on your left side with your legs in a curled position. The colonoscope has a lens and a light source that permits the endoscopist to look at a television monitor where the image is magnified many times so the endoscopist can see minute changes in tissue. The endoscope contains channels that allow the endoscopist to take biopsies and to introduce or withdraw fluid or air. Biopsies do not hurt; the lining of the colon does not have that type of pain sensation. However you may experience some cramping as air is introduced through the scope and the scope is passed through twisty segments of the colon. The air is needed to permit the endoscopist to advance the scope and see the lining of the colon. Do not be embarrassed about releasing the air through your rectum. You will be offered sedation and pain relief, this involves giving you an injection to make you relaxed and sleepy during the colonoscopy.

Before the Procedure

To allow a clear view the whole large bowel (colon) must be completely empty of waste material. It is essential that you drink 2 sachets of liquid bowel preparation to clear the bowel the day before the procedure and drink plenty of fluid. If you have a morning appointment, please follow the instructions inside the box. If you have an afternoon appointment, please follow the enclosed instructions. You may experience abdominal pain or a headache it is fine to take paracetamol or similar analgesia. Although patients worry about discomforts of the examination, most people tolerate it very well and feel fine afterwards.

Medicines and Medical Conditions

It is important you bring a list of your current medication with you so that you can give it to the nurse on arrival.

Iron tablets

If you are taking iron tablets please stop taking them for TWO WEEKS BEFORE the procedure. This is because iron coats the colon, making it difficult to see the lining.


If you are taking Aspirin please stop taking this 7 DAYS before the procedure. This is because Aspirin makes you more likely to bleed


If you are taking Warfarin tablets, please inform the Gastroenterology Unit as soon as possible, as our doctors may decide that it is necessary for you to stop taking your tablets for a limited time before the gastroscopy.


If you suffer from diabetes, please inform the Gastroenterology Unit as soon as possible, as it may be necessary to change the time of your appointment or be admitted to hospital a day before your procedure for treatment. If your diabetes is managed by your GP please contact the surgery for advice. If under the care of Elsie Bertram Diabetes Centre please contact your Diabetes specialist nurse on 01603 288513.


If you are pregnant or breast-feeding please contact the Gastroenterology Unit .


When you come to the department, the procedure will be explained and a doctor will ask you to sign a consent form. This is to ensure you understand the test and its implications / risks. 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.

After the Procedure

The endoscopist will talk to you at the end of the procedure, explaining what has been found. However, if a biopsy has been taken the results may take several days. Details of the results and any necessary treatment will be sent to your GP or a further outpatient appointment may be necessary. You will be left to rest as you may feel sleepy if you have had sedation. If you chose to have sedation it is a good idea for the person taking you home to be with your when you speak to the endoscopist. If sedation has been used, people find they forget what has been said and may not even recollect having the test at all. Once you have returned home, or back to your ward you may begin to eat and drink normally and resume your normal medication, unless instructed otherwise by the Doctor. If you have had sedation you must have someone to escort you home and stay with you for the 24 hours after your test. Following sedation you must not do any of the following for 24 hours:

  • Drive a motor vehicle
  • Drink Alcohol
  • Operate Machinery
  • Sign Legal Documents

Side Effects

Side effects of this procedure are usually minimal, sometimes patients may experience discomfort in the anal region for 24 hours, or notice a little bleeding on opening the bowels. Bleeding usually stops after 2 days. You will be given an advice sheet on after care and signs to watch for when you have had your procedure.

Risks and Complications

The main risks of colonoscopy are damage to or perforation of the colon during the procedure. This can lead to bleeding and infection, which may require treatment with medicines or surgery.

Useful Sources of Information

Additional information can be found at these websites: