What is a colonoscopy?
Your consultant has advised that you should have a colonoscopy. This is a complete examination of your large bowel (otherwise known as the large intestine or the colon).This investigation is performed using an instrument called a colonoscope. This is a long flexible tube which is about the same thickness as your little finger, it lights up the lining of your large bowel and has a sensor on the end to capture video images which are relayed back to a television screen in the room.During the investigation, it may be necessary to take some tissue samples, known as biopsies, from the lining of large bowel for further analysis. This is completely painless. Photographs may also be taken for your medical
Why do I need to have a colonoscopy?
You have been advised to undergo this test in order to try to find the cause of your symptoms, help with treatment and, if necessary, to decide on further investigations.
There are many reasons why this colonoscopy may be recommended and your consultant will have discussed these with you.
Common indications for a colonoscopy include:
- A change in your usual bowel habit to constipation or diarrhoea
- Bleeding from the back passage
- To find the cause of anaemia
- To review a known bowel condition (e.g. inflammatory bowel disease, colonic polyps)
- To assess or treat an abnormality seen on other tests such as barium enema or CT scan
- A strong family history of bowel cancer
- As part of the national bowel cancer screening program
If none of these apply to you, your doctor will explain any other reasons there may be for having this test.
Will I receive sedation?
It is important that you are comfortable during the procedure to ensure that your consultant can perform the procedure successfully.
It is usual for most people to have a sedative drugs and a painkiller to be administered into a vein in your arm which will make you drowsy and relaxed for the colonoscopy. This is known as intravenous sedation.
Alternatively, we can give you Entonox gas during the procedure which will help to ease any pain or discomfort and has a calming effect.
Intravenous sedation
Sedative drugs can be administered into a vein in your arm which will make you drowsy and relaxed for the test.
These drugs will NOT make you unconscious like a general anaesthetic. You will be in a state known as conscious sedation, which means that, although drowsy, you will still be able to hear what is said to you and will be able to follow simple instructions during the investigation, sometimes sedation can also prevent you from remembering anything about the procedure afterwards.
Your oxygen levels and heart rate will be monitored during the procedure, and your blood pressure may also be recorded. You will receive oxygen by small tubes which rest just below your nose.
If you choose to have sedation, you must arrange for a friend or relative to collect you from the hospital and we recommend that they stay with you afterwards. You must not drive, ride a bike, operate machinery, climb ladders, or sign important documents for 24 hours following sedation.
If you are not able to make these arrangements, we will not be able to give you sedation.
Entonox gas
Entonox is a colourless and odourless gas comprised of oxygen and nitrous oxide (commonly known as laughing gas). It is the same gas used by pregnant women during labour pains. It can also be beneficial during flexible sigmoidoscopy and colonoscopy because it helps to relieve pain and has a calming effect.
The gas is administered by a special mouth-piece which you will be asked to hold yourself during the procedure. A two-way valve system allows you to breathe normally through the mouth-piece. The Entonox gas begins to work within 30 seconds and you may feel slightly light headed and sleepy. You can control the amount of gas that you receive yourself by simply removing the mouth-piece but your nurse will monitor you closely throughout the procedure.
One of the benefits of Entonox is that once your procedure is over, the gas is rapidly eliminated from the body and you are usually safe to leave the department soon afterwards. Unlike with intravenous sedation, you are permitted to drive just 30 minutes after the test as long as you feel back to your normal self.
Entonox is very safe in the majority of people. It can cause mild nausea, dizziness and a dry mouth. As the effects of the drug wear off very quickly, so do these side effects. Please be aware that Entonox may not be suitable for you if you have a respiratory condition.
Some patients choose to undergo colonoscopy without any drugs but for many people the test can become very uncomfortable and occasionally intolerable in this situation.
How to prepare for your colonoscopy
It is important that your bowel is completely empty before a colonoscopy to allow adequate inspection of the lining of your colon, this is usually achieved by giving you a bowel cleansing preparation to take at home on the day before your procedure. Your consultant will have prescribed this prior to the test along with clear instructions on how to administer it. If you have any queries do not hesitate to contact the hospital and we will be happy to help you.
What happens during the procedure?
The colonoscope is introduced into the back passage and manoeuvred around the entire length of your large bowel and in some cases into the end portion of your small bowel known as the terminal ileum. There are some bends that naturally occur in the bowel and negotiating these may be uncomfortable for a short period of time but the sedation and analgesia will minimise any pain.
Air is gently passed into the bowel during the investigation to facilitate the passage of the colonoscope. You may be asked to change position during the test, to help pass the colonoscope around your bowel, and the endoscopy nurses will help you move if necessary.
We will ensure that you are well covered up throughout the procedure to preserve your dignity.
Once the colonoscope has been passed all the way around your bowel, your consultant will slowly withdraw the instrument making a close inspection of the lining of your bowel to look for any abnormalities. Some of the air blown into the bowel will be removed as well, which will ensure you remain comfortable.
During the procedure samples may be taken from the lining of your bowel, known as biopsies for analysis in our laboratories. These will be retained for future tests if they become necessary.
The whole procedure usually takes between 20 and 30 minutes but can be very variable depending on how curved your bowel is and whether any additional procedures such as polypectomy are required.
What is a polyp/polypectomy?
A polyp is a small growth that can form on the lining of the bowel. Most polyps are harmless but if they are left to grow, some forms of polyps can develop in to a cancer.
The removal of a polyp is called a polypectomy and is performed by using a variety of instruments through central channels of the endoscope.
What happens after the procedure?
You will be escorted to the recovery area or ward in order to rest while you recover from your procedure.
If you have received sedation, it usually takes about 30 minutes for the initial effects of sedation to wear off although some people may feel fully alert immediately after the procedure, while you recover your oxygen levels, blood pressure and heart rate will be monitored. However, the drugs remain in your blood system for up to 24 hours and you can intermittently feel drowsy with lapses of memory. You will need someone to escort you home and supervise you for this 24 hour period.
If you received Entonox gas during the procedure, its effects usually wear off within a few minutes. You will be observed in the department until you feel back to your normal self.
Are there any risks?
A Colonoscopy is generally regarded as a very safe test, however as with most medical procedures, there are some risks involved. Your consultant will have considered these risks and felt that the benefits of this procedure outweigh the potential risks before they suggested that you should have it carried out.
You need to be aware of the following problems which may arise:
- You may experience bloating and abdominal discomfort for a few hours after the procedure because air is used to inflate the stomach. This can often be relieved by belching.
- If you choose to have sedative drugs, these can cause your breathing to slow down or result in a fall in your blood pressure. This is the reason we do not give high doses of the drugs for the procedure. We monitor your breathing and oxygen levels carefully throughout and this rarely becomes a problem. In any case, an antidote to the sedative drugs that we use is always available and this can reverse its effects immediately.
- There is a risk of causing bleeding at the site of biopsies but this is uncommon, usually minor and usually stops on its own. Rarely, bleeding may necessitate a blood transfusion or further procedures to stop the bleeding.
- There is a risk of causing a tear (otherwise known as a perforation) with the camera. This risk is very small and can occur in 1 in 2000 cases. Please click here for help understanding this risk.
If you are worried about any of these risks, please speak to your consultant before your test.
Are there any alternatives?
An X-ray test (barium enema) or a CT scan (CT virtual colonoscopy) can be used to look at your large bowel, the main drawback of these tests is that they only provide pictures of the shape of your bowel and do not allow samples to be taken or any polyps to be removed. You would require a similar bowel preparation for these tests as well.
Your consultant will have considered a barium enema or CT virtual colonoscopy for you before asking you to have a flexible sigmoidoscopy.
If you do have questions about these alternatives, please mention them.