You have been advised to have a colonoscopy to help find the cause of your symptoms (a sigmoidoscopy is a limited examination of your large bowel).
This leaflet has been prepared from talking to patients who have the test. It may not answer all your questions so if you have any worries please do not hesitate to ask.
The staff who are doing the test will be available to answer any queries. Not every hospital does things in the same way.
What is a colonoscopy?
Colonoscopy is a test which allows the endoscopist to look directly at the lining of the large bowel (the colon). In order to do the test a colonoscope is carefully passed through the anus into the large bowel.
The colonoscope is a long flexible tube, about the thickness of your index finger, with a bright light at the end. Looking down the tube, the endoscopist gets a clear view of the lining of the bowel and can check whether or not any disease is present.
Sometimes an endoscopist takes a biopsy - a sample of the lining for examination in the laboratory.
A small piece of tissue is removed painlessly through the colonoscope, using tiny forceps.
It is also possible to remove polyps during the colonoscopy.
Polyps are abnormal projections of tissue, rather like warts, which the endoscopist will want to examine in more detail.
What should you expect?
Colonoscopy - are there any alternatives?
A colonoscopy is recommended as it is the best way of diagnosing any problems with the large bowel. A barium enema or CT colography are other possible investigations. Under some circumstances these tests may give additional information.
However, for most bowel conditions they are not as effective in providing the same level of clinical information which we may require for your diagnosis and treatment.
Also, if an abnormality is found with a barium enema, you may still need a colonoscopy to treat the problem or take biopsies (removing small pieces of tissue).
What is a sigmoidoscopy?
Flexible sigmoidoscopy is a procedure that allows your doctor to examine the rectum and the left-hand side of the colon. The flexible sigmoidoscope is a flexible tube about the thickness of your index finger.
It is inserted gently into the anus and advanced slowly into the rectum and the lower colon. It is an accurate and simple method of investigating the cause of rectal bleeding, change in bowel habit, and rectal symptoms such as pain and diarrhoea.
The preparation
You will need to have a special diet required for all patients and oral bowel preparation. See enclosed instructions.
If you are taking medication or insulin for diabetes, please telephone the diabetes sister on 0161 206 8802 between 9.30 am to 12.30pm. Please have the names of your medication to hand. The diabetic nurse will then be able to advise you of any alterations needed.
If you have a stoma bag on your abdomen, please contact the stoma team to discuss bowel preparation and alternative drainable bag on 0161 206 4204 Monday to Friday between
7.15am to 5.30pm.
When you come to the department, a nurse will explain the test to you and check that you have signed your consent form. This is to ensure that you understand the test and its implications.
Please tell the nurse or endoscopist if you have any allergies or bad reactions to drugs or other tests. They will also want to know about any previous colonoscopy you may have had. If you have any worries or questions at this stage, do not be afraid to ask.
The staff will want you to be as relaxed as possible for the test and will not mind answering any queries.
You will be asked to take off your trousers or skirt and to put on a hospital gown.
The test will always be carried out by an experienced endoscopist or a trainee under appropriate supervision. In the examination room you will be made comfortable on a couch. A nurse will stay with you throughout the test.
You will be given the option of having a sedative injection to make you sleepy and relaxed. Alternatively, you may have Penthrox as pain relief, which is non-sedating, should you wish to have it (unless your medical condition prevents this which will be reviewed by a clinician).
Penthrox is a medication used to relieve pain during Endoscopic procedures. It contains a substance called methoxyflurane, which is inhaled through a special device. When inhaled, Penthrox numbs the nerves that transmit pain signals to the brain. This helps to reduce the sensation of pain quickly and effectively. Penthrox is an off-license medication used for outpatient procedures in the United Kingdom and other parts of the world. Penthrox is inhaled through a hand-held device called a Penthrox inhaler. The healthcare provider will instruct you on how to use it correctly. It’s important to follow their instructions carefully.
Like all medications, Penthrox can cause side effects, although not everyone will experience them.
Common side effects may include:
- Dizziness or light-headedness
- Nausea or vomiting
- Headache
- Sweating
- Feeling sleepy or tired
Rare complications include:
- Persistent/increasing abdominal pain
- Failure to pass wind
- Temperature above 38 Degrees
- Vomiting blood
- Liver and kidney problems
If you experience any severe or persistent side effects, inform your healthcare provider immediately.
Important safety information
- Avoid driving if you experience dizziness or drowsiness
- Let your healthcare provider know about any other medications you are taking, as well as any medical conditions you have, before using Penthrox
Who should not use Penthrox?
Penthrox may not be suitable for everyone.
You should not use Penthrox if:
- You are allergic to methoxyflurane or any inhalation anaesthetics
- You have a history or family history of malignant hyperthermia
- You have previously experienced liver damage from methoxyflurane or other inhalation anaesthetics
- You have severe liver or kidney problems
Penthrox is an effective medication for short-term pain relief in various situations.
It provides fast relief with minimal side effects when used as directed.
If you have any questions or concerns about using Penthrox, consult your healthcare provider for further guidance.
You can get further information from:
Electronic Medicines Compendium (EMC) Penthrox:
https://penthrox.co.uk/patients/
During the test
When the tube has been gently inserted through the anus into the large bowel, CO2 and water will be passed through it to distend the colon and give a clearer view of the lining. This may give you some wind-like pains, but they will not last long.
You may get the sensation of wanting to go to the toilet, but as the bowel is empty, there is no danger of this happening. You may pass some wind but, although this can be embarrassing, remember that the staff do understand what is causing it.
It usually takes up to thirty minutes for the colon to be examined, but the test may last longer. When the examination is finished, the tube is removed quickly and easily.
After the test
If you do not have sedation, you will be able to go home immediately.
If you have had sedation, you will have to stay in the recovery ward for at least 1 hour afterwards before being allowed home. You may feel a little bloated with wind pains, but these usually settle quickly.
Going home
If you have had sedation, it is essential that someone comes to the unit to pick you up after the test. Once home, it is important to rest quietly for the remainder of the day. Sedation lasts longer than you think so you should NOT:
- Drive a car
- Operate machinery
- Drink alcohol
- Sign anything that is legally binding
The effects of the test and injection should have usually worn off after 24 hours, when most patients are able to resume normal activities.
If you live alone and have no relative who could support/care for you over the 24-hour period following your endoscopy you will not be able to have sedation.
General information
When will I know the results?
Your results will be discussed with you on the day of the test and you will receive a copy of the report on the dame day.
Risks
Colonoscopy can result in complications such as reactions to medication, perforation (tear) of the intestine, and bleeding. These complications are very rare (around 1 in 1000 for perforation and 1 in 500 for bleeding) but may require urgent treatment, and even an operation.
The risks are slightly higher when colonoscopy is used to apply treatment such as removal of polyps. Be sure to inform us if you have any pain, black tarry stools or persistent bleeding in the hours or days after colonoscopy.
If you are unsure about information given or have any other queries, please contact:
GI Endoscopy Unit
Salford Royal Hospital
9am to 5pm on 0161 206 5959/0161 206 5958
Booking Team – 01706 906788
Date of Review: October 2025
Date of Next Review: October 2027
Ref No: PI_SU_1297 (Salford)