This is an examination of your large bowel (colon).  During colonoscopy, you will usually be given sedation and analgesia (pain relief) to make you feel relaxed and drowsy.

Why do I need to have a colonoscopy?

You may have been advised to undergo this investigation of your large bowel to try and find the cause for your symptoms, help with treatment and, if necessary, to decide on further investigation.  A colonoscopy is used to investigate a variety of symptoms, for example:

  • Persistent diarrhoea
  • Abdominal pain
  • Change in bowel habit
  • Bleeding from the back passage
  • Polyps
  • Strong family history of cancer
  • Follow-up inspection of previous disease
  • Assessing the clinical importance of an abnormality seen on an X-ray.

Is there an alternative test to colonoscopy?

A barium enema examination is the main alternative investigation to colonoscopy.  It has the disadvantage that it is not as accurate and that samples of the bowel cannot be taken if an abnormality is found.  If this is the case, a subsequent endoscopic examination may be required.

What is a colonoscopy?

This test is a very accurate way of looking at the lining of your large bowel (colon) to establish whether there is any disease present.  This test also allows us to take tissue samples (biopsies) for analysis by the pathology department if necessary.

The instrument used in this investigation is flexible and is called a colonoscope.  Within each scope, there is an illumination channel, which enables light to be directed on to the lining of your bowel, and another which relays pictures back on to a television screen. This enables the endoscopist to have a clear view and to check whether or not disease or inflammation is present.

During the investigation, the endoscopist may need to take some samples from the lining of your colon for analysis.  This is painless.  The samples will be retained.  Any photographs will be recorded in your notes.

What is a polyp?

A polyp is a protrusion (lump) from the lining of the bowel.  Some polyps are attached to the intestinal wall by a stalk, and look like a mushroom, whereas others are flat, without a stalk.  Polyps, when found, are generally removed or sampled by the endoscopist as they may grow and cause problems later.  Flat polyps are generally a little more difficult to remove.


A polyp may be removed in one of two ways, both using an electrical current known as diathermy.

For large polyps a snare (wire loop) is placed around the polyp, a high-frequency current is then applied and the polyp is removed.

Flat polyps (without any stalk) can be removed by a procedure called EMR (Endoscopic Mucosal Resection).  This involves injecting the lining of the bowel that surrounds the flat polyp.  This raises the area and allows the wire loop snare to capture the polyp.

For smaller polyps, biopsy forceps (cupped forceps) are used.  These hold the polyp while the diathermy is applied, therefore destroying the polyp.

How do I prepare for the test?

It is advised that you wear loose-fitting clothing, as this is more comfortable for you during and after the test.  Please bring a dressing-gown and slippers if you can.

To allow a clear view during the test, your bowel must be empty.  Therefore it is essential that you follow the bowel preparation instructions.  The instructions are included and the bowel laxative should be started the day before the test.

It is important to increase your intake of clear fluids on the day before your test (examples of clear fluids are included at the back of this booklet).  You may drink water up to 2 hours before your test.  A list of clear fluids is also given in the bowel preparation (MoviPrep) instruction leaflet.

What about my medication?

Routine Medication

If you are taking iron (ferrous sulphate) this medication should be stopped 7 days before the procedure.

If you are taking stool bulking agents (eg Fybogel), loperamide (Imodium), Lomotil or codeine phosphate, you must stop these 5 days prior to your appointment.

All your other routine medication should be taken as normal.

If you are taking the contraceptive pill, be aware that the laxatives given to clear the colon prevent the absorption of the pill and you will need to use other forms of contraception.

Anticoagulants and Clopidogrel

Please telephone Dr Chandra’s secretary, Laura on 0118 922 6901 if you are taking anticoagulants such as warfarin or clopidogrel.


If you are diabetic, please follow the advice at the end of the booklet.

How long will I be in the Endoscopy Unit?

This largely depends upon how quickly you recover from the sedation.  You should expect to be in the unit for approximately 2-3 hours.

What happens when I arrive?

You should report to the main hospital reception on arrival.  You will then be collected by a nurse and escorted to the assessment area.  Here you will be asked a number of questions about your medical history and have your pulse and blood pressure taken.

The nurse will ensure you understand the procedure and discuss any outstanding concerns or questions you may have.

You will be asked to undress, to put on a hospital gown and your dressing-gown and slippers.

As you will be having sedation, you will not be permitted to drive home or to use public transport alone, so you must arrange for a family member or friend to collect you from the unit.  The nurse will need to be given their telephone number so that he/she can contact them when you are ready for discharge.

If you have not already done so, and are happy to proceed, you will be asked to sign your consent form at this point.

Intravenous Sedation

The sedation and a painkiller will be administered into a vein in your hand or arm, and will make you lightly drowsy and relaxed but not unconscious.  You will be in a state called co-operative sedation.  This means that, although drowsy, you will still hear what is said to you and, therefore, will be able to follow simple instructions during the investigation.  Sedation has an amnesic effect – this means you are unlikely to remember the procedure.

While you are sedated we will monitor your breathing and heart rate so changes will be noted and dealt with accordingly.  For this reason, you will be connected to a finger probe pulse oximeter, which measures your oxygen levels and heart rate during the procedure.  Your blood pressure may also be recorded.

Please note that because you have had sedation, you must not drive, take alcohol, operate heavy machinery or sign any legally-binding documents for 24 hours following the procedure, and you will need someone to accompany you home and stay with you for 24 hours.

The Colonoscopy Examination

You will be escorted into the procedure room, where the endoscopist and the nurses will introduce themselves and you will have the opportunity to ask any final questions.

The nurse looking after you will ask you to lie on your left side and will place the oxygen monitoring probe on your finger.

The sedative drugs will be administered into a cannula (tube) in your vein.

The colonoscopy involves manoeuvring the colonoscope around the entire length of your large bowel.  There are some bends that occur naturally in the bowel and negotiating these may be uncomfortable for a short period of time but the sedation and analgesia will minimise any discomfort.

Air is gently passed into the bowel during the investigation to ease the passage of the colonoscope.
During the procedure, samples may be taken from the lining of your bowel for analysis in our laboratories.  These will be retained.  Any photographs will be recorded in your notes.


Colonoscopy is an invasive investigation and because of this it has the possibility of complications. These are very rare but it is important that we tell you about them, so that you can consider this information before you consent to treatment.

Dr Chandra will have considered the risks carefully.  The risks must be compared to the benefits of having the procedure.  The risks can be associated with the colonoscopy itself and with the administration of the sedation.

Risks of the Endoscopic Procedure

The main risks of any endoscopic procedure are of mechanical damage, such as:

  • Perforation (risk approximately 1 for every 1,000 examinations) or a tear in the lining of the bowel.  An operation is nearly always required to repair the hole.  The risk of perforation is higher with polyp removal.
  • Bleeding may occur at the site of biopsy or polyp removal (risk approximately 1 for every 100-200 examinations where this is performed).  Such bleeding may either simply stop on its own or, if it does not, can usually be controlled by cauterization (sealed by heat) or injection treatment.

Risks of Sedation

Sedation can occasionally cause problems with breathing, heart rate and blood pressure.  If any of these problems do occur, they are normally short-lived.  Careful monitoring by a fully-trained endoscopy nurse ensures that any potential problems can be identified and treated rapidly.

After the Procedure

You will be allowed to rest for as long as is necessary.  Your blood pressure and heart rate will be recorded.  Should you have underlying breathing difficulties or if your oxygen levels were low during the procedure, we will continue to monitor your breathing.  Once you have recovered from the initial effects of the sedation (which normally takes 30-60 minutes) you will be offered a drink and a snack, and moved to a comfortable chair.

Before you leave the unit, Dr Chandra will explain the findings and any medication or further investigations required.  She will also inform you if you require further appointments.

The sedation may temporarily affect your memory, so we recommend you have a member of your family or a friend with you when you are given this information, although there will be a short written report given to you.

The sedative drug remains in your blood system for about 24 hours and you may feel drowsy later on, with intermittent lapses of memory.

If you live alone, you will need to arrange for someone to stay with you, or arrange to stay with your family or a friend for at least 6 hours.

If the person collecting you leaves the department, the nursing staff will telephone them when you are ready to go home.

You may return to work the next day if you feel well enough.


If you experience any of the following problems, please contact your GP immediately, informing them that you have had a colonoscopy:

  • Severe abdominal pain (not cramp caused by wind).
  • A sudden passing of a large amount of bleeding from your back passage (if a very small amount of blood, take no action).
  • A firm and swollen abdomen.
  • High temperature or feeling feverish.
  • Vomiting

Summary of Important Information

Colonoscopy is a safe procedure and a very good way to investigate your symptoms.  Risks and complications are rare and the benefits outweigh the risks.  However, it is your decision whether you wish to go ahead with the procedure, and you are free to change your mind at any time.

Checklist – things to remember before your procedure

  • Read the booklet and MoviPrep leaflet carefully.
  • Note the appointment date in your diary.
  • Wear loose-fitting clothing.
  • Bring a dressing-gown and slippers if you can.
  • Follow the bowel preparation (MoviPrep) instruction.
  • Drink plenty of fluids.
  • Have nothing to drink for 2 hours before your test.
  • Make arrangements for transport and for supervision for 6 hours.
  • Check for specific medication instructions.
  • Bring your medications with you.
  • If you are taking warfarin or clopidogrel, please ring Dr Chandra’s secretary, Kayleigh, on 0118 922 6901.

Advice for people with Diabetes undergoing a Colonoscopy

You will be given instructions for preparing the bowel with MoviPrep.  Remember, you are allowed clear fluids, which include sugary drinks (see list below).

Afternoon Appointment

If your diabetes is treated with tablets only:

Take your tablets with breakfast only on the day before the test.
Do not take your diabetes tablets on the day of the test.
Take your next dose of tablets when you are allowed to eat again.

If your diabetes is treated with insulin:

On the day before the test take the normal dose of insulin if your insulin is due with breakfast.  If you are on fast-acting insulin such as Actrapid, Humulin S, NovoRapid, Humalog, Apidra or Hypurin Neutral, take the normal dose of insulin with breakfast and 2/3 with a low-residue lunch.  Omit the evening dose.  If you are on glargine (Lantus) or detemir (Levemir) take 2/3 of the usual dose when it is due.

On the day of the test if you are taking insulin twice daily, take 1/3 of your normal morning dose if your blood sugar at that time is above 10, otherwise omit insulin.  If on fast-acting insulin, omit it.  If you are on glargine (Lantus) or detemir (Levemir) take 1/3 of the dose if normally taken in the morning.
Bring your insulin and your blood testing equipment with you to the hospital.  Take insulin after the test, once you are eating again.

Morning Appointment

If your diabetes is treated with tablets only:

Take your tablets with breakfast only on the day before the test.
Do not take your diabetes tablets on the day of the test.
Take your next dose of tablets when you are allowed to eat again.

If your diabetes is treated with insulin:

On the day before:  If you are on twice-daily insulin, take 2/3 of the normal dose of insulin with a low-residue breakfast, e.g. if your normal dose is 30 units, take 20 units instead.  If you are on fast-acting insulin such as Actrapid, Humulin S, NovoRapid, Humalog, Apidra or Hypurin Neutral, take the normal dose with your breakfast.  Omit thereafter.  For glargine (Lantus) or detemir (Levemir) take 2/3 if usually taken in the morning and 1/3 for the evening dose.  Check your blood sugar level four times during the day.  If your blood sugar is below 5, remember you can drink sugary drinks to avoid a hypo.

On the day of the test:  If you are taking insulin twice daily, take 1/3 of your morning dose of insulin if your blood sugar is above 10, otherwise do not take any insulin.  If you take glargine (Lantus) or detemir (Levemir), take 2/3 of your normal dose at the usual time.  Omit fast-acting insulin.
Bring your insulin and your blood testing equipment with you to the hospital.
Take insulin after the test once you are eating again.

Clear Fluids

Clear fluids are those that are not thickened and do not contain solid material or colouring agents.  Examples of clear fluids that are all right to drink are water, black tea or coffee (no milk), fizzy and non-fizzy soft drinks, cordials (no juice that is red or purple) and clear soups like chicken, beef or vegetable broth (strained, without any bits), gelatine (no red or purple), 100% cranberry juice (even though it is red, there is no colouring agent in it).

This information leaflet incorporates advice recommended by
The British Society of Gastroenterology.

Disclaimer: This article is for information only and should not be used as a substitute for professional medical care by a qualified doctor or other healthcare professional. ALWAYS check with your doctor if you have any concerns about your condition or treatment.