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What is a colonoscopy?

A colonoscopy is an examination performed by a highly trained and experienced endoscopist. It shows what is happening inside your colon—this is the longest part of the intestine and is often called the large bowel.


What happens during a colonoscopy?

A colonoscope, a long, thin, flexible tube containing a tiny video camera, is passed into the colon through the anus by the endoscopist. It is moved through the colon to the caecum (where the large bowel ends and the small bowel begins). In some colonoscopies, the tube is also passed into the first part of the small bowel. The camera transmits pictures onto a screen.


How long does a colonoscopy take?

About 30 minutes, but you are in the endoscopy room for about an hour.


Why might you need a colonoscopy?

A colonoscopy can be used to investigate a range of unexplained problems:

It can also be used to assess or monitor conditions such as inflammatory bowel disease.

Biopsies and treatment can be given during a colonoscopy.


What should you tell us before a colonoscopy?

Tell your consultant all the medications you take, particularly any blood thinners such as clopidogrel, warfarin, or heparin), or if you are on iron tablets.

Our general advice to patients having a colonoscopy is to:

  • Stop taking clopidogrel 7 days before your procedure.*
  • Stop taking iron tablets 7 days before your procedure.
  • Stop taking warfarin 5 days before your colonoscopy*
  • Tell us if you have diabetes, as your medication may need to be adjusted on the day of your colonoscopy.

*Please check with your GP, cardiologist or anti-coagulant clinic to see whether you need replacement medication.


How do you prepare for a colonoscopy?

Decide whether or not you will have sedation. Not all patients need sedation as the procedure is only mildly uncomfortable.

Take a bowel preparation to clear out your bowel: we can see inside the large bowel clearly only if it is empty.


What happens on the day?

Come to the endoscopy unit 30 minutes before your colonoscopy. Although we always try to perform your colonoscopy at the agreed time, sometimes there are delays so your time slot cannot be guaranteed. If there is a delay, you will be kept updated.

  • When you arrive, you will be seen by one of our nursing team, who will ask you questions about your medical history, medications and allergies. If you have decided to have your colonoscopy with sedation, a small plastic cannula will be inserted into a vein in your arm or hand.
  • You will then see your consultant, who will discuss again the details of the planned procedure, including alternatives and risks.
  • You will be asked whether you understand and accept what is planned and we will then need your written consent to go ahead with the colonoscopy.
  • If you are given sedation, a small clip will be placed on your finger to monitor your pulse rate and oxygen levels. We will also give some extra oxygen via a small tube placed into your nose.
  • Gas is gently infused into the colon to expand the bowel for the doctor to have good views. You may experience some discomfort from time to time but we aim to keep this to a minimum.
  • Any abnormal areas are photographed and we may take a small sample of tissue, a biopsy, for further analysis. Many people over 50 have bowel polyps. These are growths that are not cancerous, but if they are left alone they can sometimes become cancers. Any polyps seen during the colonoscopy can be removed if we consider that it is safe and appropriate to do so.

What are the risks of colonoscopy?

Thousands of people in the UK have a colonoscopy every year with no problems; it is a very safe procedure.

Serious complications are extremely rare during routine colonoscopy but these problems may happen:

  • A perforation in the wall of the bowel, for example, happens less than once in every 1000 procedures. You are at greater risk if you have a polyp that will need removing or if you have a tight narrowing (a stricture) in part of your bowel. In these more complex cases, the rate of perforation rises to about 1%. If a perforation does occur, you will need to stay in hospital for observation. Only some perforations need to be repaired surgically.
  • Significant bleeding following colonoscopy, even with polyp removal, is very rare, but slight bleeding often occurs at the site of a biopsy. Serious bleeding needs immediate treatment and observation in hospital. Very few patients with bleeding need surgery.

What happens after a colonoscopy?

Your throat may feel numb and slightly sore, and because of the local anaesthetic and sedation you should not attempt to eat or drink anything for at least one hour.

If you did not have sedation you may go home as soon after the colonoscopy as you wish.

If you have received sedation you should be able to leave when fully awake (usually about an hour), but you must be accompanied by a responsible adult. Sedation makes you sleepy but it also affects your judgement and the way you make decisions. If you have been sedated:

  • Do not drive home or drive for 24 hours.
  • Do not operate machinery.
  • Do not make any important decisions.
  • Do not drink alcohol.

You will be reviewed before going home, to check that all is well. Although your consultant may be able to discuss the endoscopic findings at the time, the results of biopsies may take up to four working days to be available.


Unwell after your colonoscopy?

Complications are rare but if you experience any of these problems, please seek medical advice and contact us urgently:

  • Severe persistent pain.
  • Light-headedness or fainting.
  • Passing of blood when you go to the toilet.
  • Fever.

Getting more information

If you have any questions concerning your procedure, please contact the gastroenterology/hepatology team at The Physicians' Clinic

The team is available Mon – Fri 0900-1700


Tel: 020 7034 8164

Fax: 020 7034 8140

Have you experienced problems:

  • Contact your consultant directly by telephoning The Physicians' Clinic during office hours as above.
  • Out of hours, please contact your gastroenterologist directly using the information supplied after your appointment.

Contact Us

020 7034 8164

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