What is a flexible sigmoidoscopy?

This is an examination of the left half of your large bowel (otherwise known as the large intestine or the colon).Your Consultant uses a flexible sigmoidoscope or its longer counterpart, the colonoscope for this procedure. 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 records.

Why do I need to have a sigmoidoscopy?

There are a number of reasons why this test may be recommended and your consultant will discuss 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
  • A review of 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

If none of these apply to you, your consultant will explain any other reasons there may be for having this test.

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Will I receive sedation?

Flexible sigmoidoscopy is a short test and most people will remain comfortable without sedative drugs or pain killers. If you are particularly anxious about the test, intravenous sedation or Entonox gas is can be administered.

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.

How to prepare for your sigmoidoscopy?

It is important that the left side of your bowel is completely empty before a flexible sigmoidoscopy to allow adequate inspection of the lining of your colon.
This is usually achieved by giving you an enema shortly before the procvedure. An enema is a liquid preparation which is squirted into the back passage and induces a bowel movement. This will help to ensure that the left side of your bowel is clear.

What happens during the procedure?

The sigmoidoscope is introduced into the back passage and maneuvered around the left side of your large bowel. There are some bends that naturally occur in the bowel and negotiating these may result in brief periods of discomfort.
Air is gently passed into the bowel during the investigation to facilitate the passage of the camera. You may be asked to change position during the test, to help pass the endoscope 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 sigmoidoscope has been passed around the left side of 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, known as biopsies, may be taken from the lining of your bowel for analysis.
The procedure usually takes about 10 minutes but this can vary depending on how many twists there are in your bowel, and whether any additional procedures 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.
If a polyp is found on the left side of your bowel, there is a higher chance of you having polyps on the right side of your bowel. As a flexible sigmoidoscopy does not reach the right side of your bowel, if a polyp is found you may be asked to return on another day for a full colonoscopy this allows the entire large bowel to be examined and any further polyps to be removed.
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?

Flexible sigmoidoscopy 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 may experience bloating and abdominal discomfort for a few hours after the procedure because air is used to inflate the bowel. This can often be relieved by passing wind at the back passage.
If you choose to receive sedative drugs, they 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 the procedure 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.

The most significant risks of sigmoidoscopy are:

  • Perforation (or a tear of the lining of the bowel)
  • Bleeding

The risk of perforation is less than 1 for every 15,000 procedures performed but may be higher if a polyp is removed. Please click here for help understanding this risk. Significant bleeding may occur once in every 200 to 400 procedures.
If the bowel preparation has not been effective and there is still stool in your bowel, it can hide abnormalities which can be missed.

Are there any alternatives to a flexible sigmoidoscopy?

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.

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