A colonoscopy test involves looking at the large bowel (colon) with a narrow flexible tube called a colonoscope (scope).

A colonoscopy test involves looking at your large bowel (colon) with a narrow flexible tube called a colonoscope (scope). The scope is inserted through the back passage (bottom) and passed around the bowel. The procedure is performed by, or under the supervision of, a trained doctor or nurse (endoscopist). A light and camera at the end of the scope relay pictures onto a television screen. Carbon dioxide is used to inflate the bowel and help the endoscopist see better.
Samples of tissue (biopsies) may be taken during the test. This is done through the scope. It does not cause any pain and the samples are kept to be looked at under a microscope in the laboratory. Photographs may also be taken for your medical records and may be used for teaching purposes.
The procedure generally takes about 30 to 40 minutes but may take up to an hour.

What are the benefits of having a colonoscopy?
If you have been troubled by symptoms, the cause may be found and help decide if you need treatment or further tests.
If a polyp is found this can often be removed during the procedure (there is more information about polyps on page 11 of this booklet).
Colonoscopy may be done as a follow up inspection if you have had a polyp in the past or other disease of the large bowel.
If a scan or x-ray has suggested there may be something wrong in the large bowel, a colonoscopy allows a closer look at the area.

What are the risks of the procedure?
Complications are rare. These may be linked to the procedure itself or the sedation medicine.
Perforation or tear of the bowel (about 1 for every 1,500 cases). If this happens you may need an operation.
Bleeding may happen where a biopsy is taken or a polyp removed (about 1 for every 150 cases). This can happen up to 2 weeks after the procedure. It usually stops on its own but may need cauterisation or injection treatment. In some cases a blood transfusion may be needed.
There is a small chance that a polyp or cancer may not be seen (about 5 in every 100 cases). This might be because the bowel was not completely empty or, on rare occasions, that the endoscopist missed seeing it.
There is also a small chance (about 10 in every 100 cases) that the endoscopist may not be able to pass the scope along the entire length of the bowel and a different investigation will be needed.
Sedation can sometimes cause problems with breathing, heart rate and blood pressure. If any of these problems do occur, they are usually short lived. Careful monitoring by a specially trained endoscopy nurse means that potential problems are picked up early and dealt with quickly.
In extremely rare cases the procedure can lead to death. Current evidence suggests that this may happen in around one out of every 10,000 procedures.

What are the alternatives?
CT colonography (virtual colonoscopy) is another way to look at the large bowel. This is carried out in the x-ray department and involves radiation exposure. The test has limitations. If something abnormal is seen in the large bowel, a colonoscopy may still be needed to look at the area.

Preparing for the investigation
To reduce the risk of complications and to give clear views, your stomach and bowel must be empty. You will have been prescribed a laxative medication (also called ‘bowel preparation’) which will cause you to pass watery stools. Please read the leaflet that is in the packet of laxative but follow the instructions provided in this booklet for when to take it. You will find the instructions later in the booklet starting on page 14. Different medications are used so it is important to follow the instructions for the particular medication prescribed for you.
The instructions are different for a morning or afternoon appointment so please make sure you check your appointment time.
If, since the laxative was prescribed for you, your health has become worse in any way or you feel you will not be able to drink the amount of fluid advised, please contact the endoscopy department before you start taking it.
Please make sure you read all of the instructions for your particular appointment and laxative a few days before your appointment. It is important that you follow the instructions given, especially the amount of fluid you should drink, as the laxative can cause you to become dehydrated.
Symptoms of dehydration include dizziness or light-headedness (particularly on standing up), thirst, headache or reduced urine production (passing less water).

How long will I be in the Endoscopy department?
Overall you may expect to be in the department for 1 to 3 hours. The department deals with emergency patients too and they will take priority if needed.

What if I take regular medication?
If any of your regular medication needs to be stopped before the procedure, the person who booked the test should have discussed this with you. Most medication should be continued as normal, however, you must try to take it at least one hour before or after the laxative. If you are taking the oral contraceptive pill you should take other precautions for the week following your test.
If you are taking iron tablets you should stop these 5 days before the procedure. If you are taking Fybogel, Regulan, Proctofibe, Loperamide (Imodium), Lomotil or Codeine, please stop taking these 3 days before.
If you rely on strong pain killers which cause you to become constipated and you would find it difficult to stop them before the test, please speak to your GP as you may need a regular laxative for a few days before you start taking the bowel preparation.
Blood thinning medications (anticoagulants)
Sometimes these medications need to be stopped and if this is the case the person who referred you for the test should have given you clear instructions. If you are unsure please contact your consultant’s secretary. For your safety, if the correct instructions are not followed, it may not be possible to do the colonoscopy and you may have to return on another day.
Warfarin: unless you have been advised to stop this medication, continue taking it and have your INR checked within the week before the test. The procedure may be cancelled if your INR has not been checked within the last 7 days. It should be within your target range. If you have been advised to stop your Warfarin you should do so for 5 full days before the procedure and have your INR checked the day before the procedure. It needs to be less than 1.5 for the procedure to go ahead. Please bring your yellow book to the appointment.
Dabigatran, Rivaroxaban, Apixaban or Edoxoban: please do not take on the morning of the procedure. If you have been advised to stop taking this medication you should do so for 2 full days before the procedure.
Clopidogrel (Plavix), Prasugrel or Ticagrelor: these medications can generally be continued but if you have been advised to stop you should do so for 5 full days before the procedure.

If you have diabetes controlled on insulin or tablets, please make sure the endoscopy appointments team is aware so that a morning appointment can be arranged for you if possible. You will find more advice on page 12 of this booklet.
What happens when I arrive?
When you arrive for your appointment please book in at reception. It is our aim for you to be seen as soon as possible after your arrival. However, if the department is very busy your appointment may be delayed. The department looks after emergency patients who will be seen first if needed.
A nurse will take you through to the admission room and ask you about your general health to check if you are fit to have the procedure. You will also be asked about your plans for getting home afterwards.
The nurse will make sure you understand the procedure and discuss any further concerns or questions you may have. If you have not already done so and you are happy to go ahead, you will be asked to sign your consent form.
Your blood pressure and heart rate will be checked and you will be asked to remove your lower clothes and put on a hospital gown.
A cannula (small plastic tube) will be inserted into a vein so that medication can be given during the procedure (sometimes this is done in the procedure room).

If you have sedation for the procedure you will not be able to drive afterwards and it is advisable not to use public transport (further important information about sedation is given on page 10 of this booklet). It is essential that you arrange for someone to collect you. Please give the nurse their telephone number so that we can ring them when you are ready to go home.

What will happen during the procedure?
The nurse will take you through to the procedure room where you will be able to ask any final questions. A blood pressure cuff will be placed on your upper arm (this will be checked regularly throughout the procedure) and an oxygen monitoring probe on your finger. You will be asked to lie on your side with your knees bent. You will receive oxygen through the nose and if you are having sedation it will be given into the cannula in your vein.
The endoscopist will usually examine your back passage with a gloved finger before inserting the scope. The bowel has natural bends which may cause some discomfort or tummy ache but this is usually well tolerated and should not last long. You may also feel bloated due to the gas that is used.
You may be asked to change your position during the procedure as this can help with the passage of the scope.

What happens after the procedure?
After the procedure you will be taken through to the recovery area where you will be allowed to rest. Your heart rate, oxygen levels and blood pressure will continue to be monitored and when the recovery nurse feels you are ready you will be able to get dressed. You will be given a drink and a biscuit before the cannula is removed.
Before you leave the department the nurse or doctor will explain the findings and if any medication or further tests are required.

Conscious sedation
Conscious sedation is often given for this procedure to improve your comfort and is generally administered with a pain killer into a vein in your hand or arm. This will not make you go to sleep but should help you feel more relaxed.
It is important that you are awake for the procedure so that you can change position if required and tell us if you feel any discomfort.
Some people prefer not to have a sedative or pain killer for the test. If you wish to start the procedure without intravenous medication you may do so. It can be administered part way through the test if you feel you need it. Because it is given into the vein, it works within a few minutes.

‘Gas and Air’ (Nitrous Oxide) is also available for pain relief. This is a gas that you inhale through a mouthpiece and can be used in addition to, or instead of, medication into the vein. If you have Nitrous Oxide you will need to wait for at least 30 minutes before you can return to normal activities such as driving. If you would like more information please ask the admitting nurse.
Please note if you have sedation into the vein, you will need someone to accompany you home and stay for at least 4 hours and if possible overnight. You are not allowed to take part in the following activities for 24 hours afterwards:

  • drive a vehicle
  • go to work
  • look after children on your own
  • operate heavy / dangerous machinery
  • drink alcohol
  • sign legally binding documents

What happens if a polyp is found?
A polyp is an overgrowth of cells on the inner lining of the bowel. Polyps may be raised on a stalk like a mushroom (pedunculated) or flat (sessile). Polyps are generally removed or sampled (biopsied) by the endoscopist as they could grow over time and cause problems in the future. This does not cause any pain.
Polypectomy (removal of a polyp)
Polyps with a stalk are usually removed using a wire loop (snare) which is placed around the stalk. Heat is passed through the wire which cuts through and cauterises any blood vessels. Flat polyps are often removed by injecting the tissue around the polyp with fluid to raise the area away from the deeper layers. A hot wire snare is then used to remove the polyp.
Smaller polyps may be removed with a cold wire snare or pinched off the bowel wall with forceps. Polyps are sent to the laboratory to be looked at under a microscope. Your consultant may write to you with the results or give them to you at your next clinic appointment if you have one. You may also contact your GP. Routine results are usually available within 2-4 weeks but can sometimes take a little longer.

What are the risks of removing polyps?
After removal of a polyp there is a risk of bleeding and/or a hole forming in the bowel wall while the area heals. The healing process can take up to 2 weeks. It is advisable not to travel abroad for this period if large polyps are removed. Please tell the nurse or doctor if you have plans for travel after your procedure.

In most cases you can resume normal activity afterwards but if you have a large polyp removed you may be advised to avoid heavy lifting or strenuous exercise for 2 weeks to reduce the risk of complications. It is important to attend the accident and emergency department if you pass any fresh blood or clots (more than a few tablespoons) or if you have severe pain and swelling in the abdomen (tummy) which persists and does not get better.

Specific instructions for people with diabetes
Treatment with diet alone
If you control your diabetes with diet alone, you simply need to follow the instructions given at the end of this booklet to prepare for your colonoscopy.
Treatment with tablets and/or insulin
You should inform the endoscopy appointments team about your diabetes and request a morning appointment. If needed please contact the Specialist Diabetes team for advice on 01522 573074.
Please follow the bowel preparation instructions given later in this booklet and consider the following advice.
Adjusting your diabetes medication to prevent hypoglycaemia
You may need to adjust your diabetes medicines the evening before and the morning of the procedure to reduce the risk of hypoglycaemia (low blood sugar level). Your blood sugar may be higher than usual but this is only temporary to maintain your blood sugars during the procedure and you should be back to your usual level within 24 to 48 hours. Please contact the Diabetes Nursing Team (01522 573074) well in advance of your appointment for advice.
Carrying glucose to treat hypoglycaemia
On the day before and day of the procedure carry glucose tablets in case of hypoglycaemia. As these are absorbed quickly through the tissues of the mouth if sucked, they will not interfere with the procedure. If you have symptoms of low blood sugar take 4 to 6 tablets initially, followed by a further 4 to 6 if your blood sugar remains low after 10 minutes.

Blood glucose monitoring
If you usually test your blood sugar levels, check them as usual on the morning of the procedure and carry your testing kit with you to the appointment. If you do not usually test your blood, do not worry, your blood sugar will be checked when you arrive for the procedure.
Please report to the nursing staff if you have needed glucose before arriving and inform them immediately if you feel ‘hypo’ at any time during your visit.
If you take tablets for diabetes (no insulin)
Day before colonoscopy
The evening before the procedure aim to replace your usual carbohydrate intake from the list of permitted clear fluids (these can be found in the section on bowel preparation). You can have sugary fluids such as sports drinks, clear apple juice or clear jelly (NOT low sugar)
If you usually check your own blood sugar monitor this approximately every 2 hours If you take Metformin do not take it the evening before and the morning of the procedure
The day of the colonoscopy
You should continue to monitor your blood sugar and take clear sugary fluids to maintain your blood glucose level
If you are on insulin
Day before colonoscopy
The evening before the procedure replace your usual carbohydrate intake with sugary fluids from the list given in the bowel preparation section of this leaflet

You may need to adjust your insulin dose while taking the bowel preparation to prevent your blood glucose levels dropping too low. If you are unsure how to do this please contact the Specialist Diabetes Nursing Team for advice on 01522 573074
The day of the colonoscopy
You may need to reduce your morning insulin dose
You should continue to monitor your blood sugar and take clear sugary fluids to maintain your blood glucose levels
How to take your bowel preparation (laxative)
On the following pages are instructions for how to take each type of bowel preparation. These are different for morning and afternoon

What must I remember?
If you are unable to keep your appointment please notify the endoscopy department as soon as possible
It is our aim for you to be seen as soon as possible after your arrival. However, the department is very busy and your appointment may be delayed. If emergencies occur, these patients will be seen before less urgent cases
If you have sedation please arrange for someone to collect you and for someone to stay overnight if possible

Frequently asked questions

More sedation?
We work to national guidelines depending on age and health. The sedation will not make you sleep but helps to make you feel relaxed
Can I return to work after the procedure?
Patients who opt-out of sedation can return to work if they feel fit and able. If sedation is chosen then it is advised that they do not return to work for 24 hours afterwards