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Flexible sigmoidoscopy

A flexible sigmoidoscopy is a procedure that is used to look inside the rectum (back passage) and lower part of your large bowel.

You will meet the doctor carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

A flexible sigmoidoscopy allows your doctor to look inside your rectum and lower part of your bowel. He or she will do this using a narrow, flexible, tube-like video camera called a sigmoidoscope.

A flexible sigmoidoscopy is usually carried out at an endoscopy clinic in a hospital. You probably won’t need an anaesthetic or any sedation but this will vary from person to person.

If your doctor finds polyps during your flexible sigmoidoscopy, he or she may remove them or take a biopsy. A biopsy is a small sample of tissue. This will be sent to a laboratory for testing to determine the type of cells and if they are benign or malignant (cancerous).

Flexible sigmoidoscopy is very accurate at detecting polyps and cancer in certain areas of your bowel. There is evidence to show that using it for screening and polyp removal reduces the number of people who develop bowel cancer. This is currently being piloted in certain regions in the UK as part of the NHS Bowel Cancer Screening Programme.

Screening aims to detect polyps and bowel cancer before symptoms develop. People aged 55 to 60 are being offered a one-off test to look for polyps that could develop into bowel cancer if they aren’t treated. After the age of 60, the screening programme offers a faecal occult blood (FOB) test every two years. Bowel cancers and polyps may sometimes bleed and the FOB test can pick up tiny amounts of blood that you can’t usually see in faeces.

It’s important to remember that neither test is completely reliable. See your GP is you have any symptoms, such as a change in your bowel habit or persistent bleeding from your rectum.

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  • Preparation Preparing for a flexible sigmoidoscopy

    Your doctor will explain how to prepare for your examination.

    If you usually take certain medicines or supplements, you may be asked to stop taking them for up to two weeks before the procedure. These include:

    • iron tablets
    • codeine phosphate
    • medicines that bulk out your faeces, such as ispaghula husk (eg Fybogel)

    If you usually take other medicines, continue to take these as usual unless your doctor specifically tells you not to. It’s important to tell him or her if you take warfarin or any other anticlotting medicines, or if you have any allergies. If you're unsure whether or not to stop taking any of your usual medicines, ask your doctor for advice.

    Your bowel must be empty for your doctor to be able to see it clearly so you will need to have an enema. You will probably be sent this with full instructions and will need to carry it out at home before you come to the hospital. You can eat and drink as usual until you have the enema. You may be asked to have only clear fluids, for example water, clear soup or tea without milk, after doing it.

    If you’re not able to give yourself the enema at home, you can have it at the clinic or hospital just before the procedure.

    Your doctor will discuss with you what will happen before, during and after your procedure. This is your opportunity to understand what will happen. You can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead. You will be asked to do this by signing a consent form.

    Bupa On Demand: Sigmoidoscopy

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  • Alternatives What are the alternatives to flexible sigmoidoscopy?

    Depending on your symptoms and circumstances, it may be possible to investigate your bowel condition using a different test. The alternatives are described below.

    • Barium enema. This involves placing a fluid containing barium (a substance which shows up on X-rays) into your bowel via your rectum. X-ray images of your abdomen (tummy) then show the inside of your bowel more clearly.
    • Virtual colonoscopy (CT colonography). This involves having a CT scan of your abdomen. The CT scan uses X-rays to produce three-dimensional images of your lower bowel (colon) and rectum.
    • FOB test. This looks for blood in a sample of your faeces (stool sample).
    • Colonoscopy. This is similar to a flexible sigmoidoscopy but looks at the whole of your large bowel.
    • Rigid sigmoidoscopy. This allows your doctor to look at the lower part of your rectum.
    • Proctoscopy. This is an examination of your anal canal (the end of your rectum) using a tube that is about 10cm long.

    You may need to have more than one test to get a diagnosis. Your doctor will explain your options to you.

  • The procedure What happens during a flexible sigmoidoscopy?

    You may be asked to put on a gown before your procedure.

    A flexible sigmoidoscopy usually takes between 10 and 20 minutes but you will probably be in hospital for one to two hours in total. The procedure may be uncomfortable, but shouldn't be painful.

    You probably won’t need a sedative (this relieves anxiety and helps you to relax) for this procedure. However, if you do, it will be given to you as an injection into a vein in your hand or arm.

    You will be asked to lie on your left-hand side with your legs bent. Your doctor will gently examine your rectum by inserting a gloved finger. He or she will then carefully insert the sigmoidoscope into your rectum. Your doctor will use lubricating jelly to make this as comfortable as possible.

    Air or carbon dioxide gas will be passed through the sigmoidoscope into your lower bowel to make it expand. This makes it easier to see your bowel wall but can cause slight abdominal cramps in some people. You may also feel an urge to go to the toilet or pass wind.

    A camera lens at the end of the sigmoidoscope will send pictures from the inside of your bowel to a screen. Your doctor will look at these images and, if necessary, take a biopsy and/or remove any polyps you have. This is done by passing instruments through the sigmoidoscope and shouldn't cause you any pain.

  • Bowel treatment on demand

    You can access a range of our health and wellbeing services on a pay-as-you-go basis, including bowel treatment.

  • Aftercare What to expect afterwards

    If you haven't had a sedative, you will usually be able to go home when you feel ready.

    If you have had a sedative, you will need to stay a little longer. A nurse will monitor your blood pressure and pulse while you recover. You will need to arrange for someone to drive you home. Sedation temporarily affects your co-ordination and reasoning skills, so you must not drive, drink alcohol, operate machinery or sign legal documents for 24 hours afterwards. If you’re in any doubt about driving, contact your motor insurer so that you’re aware of their recommendations, and always follow your doctor’s advice.

    Before you leave, your doctor or nurse may explain what he or she saw inside your bowel during the procedure. If you have had a biopsy or polyps removed, the results will be ready after a few days. These will usually be sent to the doctor who requested your test who will discuss them with you.

    Once you get home, it's sensible to take it easy for the rest of the day. You should feel able to resume your usual activities the following day.

  • Risks What are the risks?

    As with every procedure, there are some risks associated with a flexible sigmoidoscopy. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your doctor to explain how these risks apply to you.


    Side-effects are the unwanted but mostly temporary effects you may get after having the procedure. After a flexible sigmoidoscopy, you may have abdominal cramps or feel bloated. This usually settles after a few hours. Contact your doctor if the pain continues for longer than this.


    Complications are when problems occur during or after the procedure. Possible complications of a flexible sigmoidoscopy are listed below.

    • A tear in your bowel (bowel perforation). Although very rare, this can happen during the procedure, particularly if your doctor has removed a polyp or taken a biopsy. You may need an operation to repair your bowel.
    • Bleeding. This is most likely if you have had polyps removed or a biopsy taken. This usually stops on its own within a few days. If you have any heavy bleeding, contact the hospital where you had the procedure.
    • Sedatives can occasionally cause problems with your breathing, blood pressure and heart rate. You will be monitored while you’re under sedation and during your recovery.

    It's possible that your test may not be completed successfully and you may need to have a further procedure.

  • Pros and cons Pros and cons

    This information is intended to help you understand the advantages and disadvantages of flexible sigmoidoscopy. Think about how important each particular issue is to you. You and your doctor can work together to make a decision that's right for you. Your decision will be based on your doctor’s expert opinion and your personal values and preferences.


    • Flexible sigmoidoscopy is very accurate at finding polyps and cancer in certain areas in your bowel.
    • The procedure has been found to reduce the number of people dying from bowel cancer.
    • You won’t need an anaesthetic or sedative for flexible sigmoidoscopy because it’s usually painless.
    • If your doctor finds any polyps during your procedure, they can be removed at the same time.


    • You will need to have an enema before the procedure, which can be unpleasant.
    • There is a small risk of getting a tear in your bowel or some bleeding with flexible sigmoidoscopy.
    • Flexible sigmoidoscopy can only detect abnormalities in certain areas of your bowel so you may need further tests.
  • FAQs FAQs

    What are polyps and why do they have to be removed?


    Polyps are small growths inside your bowel. They are common and don’t usually cause any symptoms or problems. However, in some people certain types of polyp can change into cancer. Therefore, if your doctor finds any polyps during your flexible sigmoidoscopy, he or she will usually remove them.


    Polyps are small lumps that range from a few millimetres to several centimetres in size. They are very common – about one in every four people develops a polyp at some time in their life. Some polyps are raised on a stalk and look a bit like a mushroom, whereas others are flatter and have no stalk. You may have just one polyp or several.

    Most polyps never cause any problems. However, there is a risk that over time a polyp will develop into a cancer. Therefore, your doctor will probably remove any polyps that he or she finds during the flexible sigmoidoscopy.

    Your doctor may remove all your polyps at the same time. Small polyps can be removed by using forceps, which are similar to tongs. For larger polyps, your doctor will place a wire loop over or around it and then pass an electrical current through the wire. This heats it and cuts off the polyp. If a polyp is too large to be removed with sigmoidoscopy, your doctor will advise you about alternatives. You may need to go back for another sigmoidoscopy or a colonoscopy.

    You won't feel any pain when the polyps are being removed. After your doctor has removed the polyp, he or she will send it to a laboratory for testing. Depending on the results of the tests, you may need further treatment or another procedure (a sigmoidoscopy or a colonoscopy).

    Is a flexible sigmoidoscopy better than a barium enema?


    barium enema is another kind of test that can be used to diagnose bowel conditions. It's used less frequently now because other, more accurate tests are available. Sigmoidoscopy is useful because your doctor can directly see the lining of your bowel. He or she can also remove polyps or take biopsies (samples of tissue) during the procedure.


    One of the tests available to diagnose bowel conditions is a barium enema. Flexible sigmoidoscopy and barium enema can both be used to show polyps and abnormalities on the inside of your bowel. Your doctor will take into account your age, symptoms and your general health to help you choose the best option.

    A barium enema X-ray involves placing a fluid containing barium (a substance which shows up on X-rays) into your bowel via your rectum. X-ray images of your abdomen (tummy) then show the inside of your bowel more clearly. The test is done in hospital and you will need to have an empty bowel for it to work well. When the barium and air are put into your bowel any abnormalities on your bowel wall will show up.

    The results of a barium enema aren’t always clear and problems may be missed. This means that you may need to have further procedures in addition to the barium enema to confirm a diagnosis. However, a barium enema has the advantage of allowing your entire bowel to be examined.

    A great advantage of a sigmoidoscopy is that during the procedure your doctor can remove polyps or take a biopsy. If polyps or other abnormalities are found with a barium enema, you may also need to have a sigmoidoscopy or colonoscopy to remove them or take biopsies. 

    What is a bowel perforation?


    Sigmoidoscopy is generally safe and complications are very uncommon. However, a very small number of people may get a tear in their bowel during the procedure – this is called a bowel perforation. You may be advised to have surgery to repair this.


    As with any procedure, there are risks associated with flexible sigmoidoscopy.

    There is a risk that during the sigmoidoscopy your bowel could be perforated. Although this can be serious it’s rare. Perforations can be caused by:

    • too much pressure from the air put into your bowel during the procedure
    • the sigmoidoscope when it’s put into your colon and moved through your bowel
    • having polyps removed or biopsies taken

    Most people who have a perforation will need to have an operation to repair it. This may be keyhole (laparoscopic) or open surgery. The symptoms of a more serious tear in your bowel are abdominal swelling and pain. If you have these symptoms after having a sigmoidoscopy, it's important to seek urgent medical attention.

    The chances of having problems during or after a sigmoidoscopy are specific for you and differ for every person. Ask your doctor to explain how these risks apply to you.

  • Resources Resources

    Further information


    • Flexible sigmoidoscopy. National Digestive Diseases Information Clearinghouse (NDDIC)., published April 2012
    • Flexible sigmoidoscopy. Medscape., published March 2012
    • The management of gastric polyps. British Society of Gastroenterology., published February 2010
    • Colon and rectal cancer screening (beyond the basics). UpToDate., published January 2013
    • About bowel screening. NHS Bowel Cancer Screening Programme., accessed 4 November 2013
    • Colorectal cancer. BMJ Best Practice., published December 2013
    • Computed tomographic colonography (virtual colonoscopy). National Institute for Health and Care Excellence (NICE), June 2005.
    • Rigid sigmoidoscopy. Medscape, published March 2012
    • How colon and rectal cancers are diagnosed. Macmillan Cancer Support., published July 2012
    • Flexible sigmoidoscopy. British Society of Gastroenterology., accessed 6 November 2013
    • Sigmoidoscopy. Johns Hopkins Medicine., accessed 6 November 2013
    • Polyps in the bowel. British Society of Gastroenterology., accessed 6 November 2013
    • Imaging in colon polyps. Medscape., published May 2011
    • Colonic polyps. Medscape., published June 2012
    • Colonoscopic polypectomy and endoscopic mucosal resection: a practical guide. British Society of Gastroenterology., published 2008
    • Barium enema examination. PatientPlus., published April 2011
    • Colorectal cancer: the diagnosis and management of colorectal cancer. National Institute for Health and Care Excellence (NICE), November 2011.
    • X-ray (radiography) – lower GI tract. Radiological Society of North America., published March 2013
    • Johnson BA. Flexible sigmoidoscopy: screening for colorectal cancer. Am Fam Physician 1999; 59(2):313–24.
    • Intestinal perforation. Medscape., published April 2013
    • Evaluation of flexible sigmoidoscopy as an investigation for ‘left-sided’ colorectal symptoms. Postgrad Med J 2004; 80:104–06. doi:10.1136/pmj.2003.008540
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