Flexible sigmoidoscopy

Expert reviewer, Ian Arnott, Consultant Gastroenterologist
Next review due, July 2022

Flexible sigmoidoscopy is a procedure that’s used to look inside the lower part of your large bowel. It can be used to check your bowel for signs of cancer and to investigate symptoms such as bleeding from your bottom.

The procedure uses a flexible tube with a camera on the end, called a sigmoidoscope. This is inserted into your back passage, to take images inside your bowel.

Patient talking with a doctor

Why do I need a flexible sigmoidoscopy?


If you live in England, you might be invited for a flexible sigmoidoscopy as part of the bowel cancer screening programme. It’s known as ‘bowel scope screening’ in this programme. The procedure is initially being offered to men and women when they turn 55, but is not yet available everywhere in England.

Bowel scope screening is used to look for and remove growths called polyps or adenomas from your lower bowel. If they are left, these growths can sometimes turn into cancer. For more information, see our FAQ: What are polyps, and why do they need removing? Bowel screening with flexible sigmoidoscopy has been shown to reduce the number of people who develop bowel cancer, and the number who die from it.

Other reasons for a sigmoidoscopy

There are several other reasons why your doctor may recommend that you have a flexible sigmoidoscopy. These include:

  • investigating symptoms affecting your lower bowel — such as bleeding from your bottom or a change in your bowel habits (for example, needing to go more often, diarrhoea or constipation)
  • monitoring existing problems in your bowel — like ulcerative colitis and Crohn’s disease — for any changes
  • evaluating bowel cancers before surgery
  • treating volvulus — a condition in which your intestine becomes twisted and causes an obstruction of your bowel

Giving your consent

You’ll meet the doctor or nurse carrying out your procedure beforehand, and they’ll discuss everything with you in detail. They’ll explain exactly what will happen during the procedure, what to expect afterwards and if there’s any risk of potential complications. You should be given time to make sure you understand everything and have an opportunity to ask any questions. If you’re happy to go ahead with the procedure, you’ll be asked to sign a consent form. This is why it’s important to make sure you feel properly informed.

If you’re invited for a sigmoidoscopy as part of bowel screening, you’ll be sent an information leaflet outlining the benefits and risks of the procedure. You’ll also be sent the consent form, which you’ll need to sign and bring to your appointment if you decide you’re happy to go ahead.

Some units where flexible sigmoidoscopy is carried out are JAG accredited. JAG stands for the Joint Advisory Group on Gastrointestinal Endoscopy. A unit with JAG accreditation will have been assessed as having high-quality services that meet all the JAG criteria for performing endoscopy procedures.

What are the alternatives to flexible sigmoidoscopy?

There are several alternatives to having a flexible sigmoidoscopy that your doctor may recommend, depending on your symptoms and general health. The main ones are listed below.

  • Colonoscopy. This is similar to a flexible sigmoidoscopy, but it’s used to look at the whole of your large bowel, not just the lower part. For more information, see our FAQ: Are sigmoidoscopy and colonoscopy different?
  • CT colonography, also known as a virtual colonoscopy. This involves having a CT scan of your large bowel. Gas is gently pumped into your back passage while you have the scan, to stretch your bowel and allow detailed images to be taken.
  • Proctoscopy. This is like a sigmoidoscopy, but it only looks at the very end of your bowel.

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

Preparing for a flexible sigmoidoscopy

You’ll usually have a flexible sigmoidoscopy as an outpatient. This means you can go home the same day and usually won’t need to stay overnight in hospital. If you’re having a sedative, you’ll need to arrange for someone to drive you home and stay with you for a while. A sedative can make you feel drowsy for some time, so you won’t be able to drive yourself until the day after your sigmoidoscopy.

Medicines to stop

You’ll be given clear instructions about how to prepare for your sigmoidoscopy. If you’re taking iron tablets or any medicines that may cause constipation, you’ll be asked to stop taking these about a week before the procedure. This will help to make sure your bowel is clear, and any problems can be easily seen. You should contact the hospital where you’re having the procedure if you’re taking medicines that thin your blood, such as clopidogrel and warfarin.

Having an enema

You’ll usually need to have an enema. This is a liquid that is injected into your back passage to flush out your bowel, so your doctor has a clear view inside. You might be able to do the enema yourself at home before you come in for your sigmoidoscopy. If you’re going for screening, you’ll be sent one with your invitation letter. Or, you may have the enema at the clinic or hospital just before the procedure. Sometimes you may be asked to take a laxative rather than have an enema. A laxative is a liquid that you drink, and also works to clear your bowel.

You might also be asked to restrict your diet to certain foods, or to fast completely before the procedure. You should be able to still have clear fluids to drink. If you’re not sure what you can eat or drink, contact the unit to ask.

At the hospital

A flexible sigmoidoscopy is usually done in an endoscopy unit at a hospital. When you arrive, you’ll be seen by a nurse who will check your temperature, blood pressure, breathing and heart rate. You’ll also meet the doctor or nurse carrying out the procedure, and you’ll be able to ask any final questions you may have. You’ll be given a hospital gown to change into, and sometimes a pair of paper shorts to wear.

What happens during a flexible sigmoidoscopy?

The flexible sigmoidoscopy procedure usually takes between five and 15 minutes. It can be done by a specially trained doctor or nurse.

You don’t usually need to have an anaesthetic or sedative for a flexible sigmoidoscopy. Although the procedure can be uncomfortable at first, it isn’t usually painful. You can choose to have a sedative if you’d like to. A sedative will make you feel more relaxed and a bit drowsy, but you’ll remain awake during the procedure. If you decide to have one, it will be given as an injection into a vein in your hand or arm before the procedure.

You’ll be asked to lie on a bed, on your left-hand side with your legs bent. Your doctor or nurse will first gently examine your back passage. They will then carefully insert the sigmoidoscope, using lubricating gel to make it as comfortable as possible.

To make it easier to see, the doctor or nurse may pass small amounts of gas and water through the sigmoidoscope into your lower bowel. This will make your bowel expand a little and can make you feel a bit bloated.

During the procedure, your doctor or nurse will be able to see images from the sigmoidoscope on a screen. They will gently guide the sigmoidoscope through your bowel, taking images and examining the lining of your bowel as they go. They will also be able to take small samples from the lining of your bowel (biopsies) if needed, and may remove any polyps they find. This is done by passing instruments through the sigmoidoscope.

If you do find the procedure particularly uncomfortable at any stage, tell your doctor or nurse and they will stop or change what they’re doing. You may be offered pain relief with Entonox (‘gas and air’), which you breathe in through a mouthpiece.

What to expect afterwards

You might feel bloated or have some mild cramping pain after the procedure. This is caused by the gas used during the procedure and usually settles down after a few hours.

If you haven't had a sedative, you’ll be able to go home as soon as you feel ready.

If you have had a sedative, you’ll be monitored for a couple of hours in the endoscopy unit while you recover. You’ll need to have a responsible adult who can drive you home and stay with you for the rest of the day.

Before you leave, your doctor or nurse may talk to you about how the procedure went and whether they removed any polyps. You may also be given an endoscopy report straight away. If you’ve had a biopsy or had polyps removed, you may have to wait up to two weeks to get the results. These may be sent to both you and the doctor who requested your test. Or, you may be asked to make a follow-up appointment to go through your results.

Complications of flexible sigmoidoscopy

Complications are when problems occur during or after the flexible procedure. As with any procedure, there are some risks associated with having a flexible sigmoidoscopy. However, these are very rare. If you’ve had a sedative during the procedure you will be closely monitored. Sedatives can occasionally cause problems with your breathing, blood pressure and heart rate.

Other important complications related to flexible sigmoidoscopy are listed below.

  • Bleeding. This is most likely if you have had polyps removed or a biopsy taken. This usually stops on its own without any treatment. Rarely — in about one in 3,000 people — bleeding can become more serious. If this happens, you may need to go into hospital for surgery.
  • A tear in your bowel (bowel perforation). If this happens, it’s likely you’ll be admitted to hospital to have an operation to repair it.
  • Infection.

If you have any of the following symptoms, contact the hospital or unit where you had the procedure straight away:

  • severe pain
  • heavy or continuous bleeding from your back passage
  • blood in your poo
  • high temperature, or generally feel unwell

Frequently asked questions

  • Flexible sigmoidoscopy and colonoscopy are similar, but a flexible sigmoidoscopy uses a shorter instrument to look inside the lower part of your large bowel only. A colonoscopy uses a longer instrument to look at the whole of your large bowel. Both tests are used to check for signs of bowel cancer.

    As a colonoscopy looks further into your large bowel, it can be more uncomfortable, and you’re more likely to need a sedative. Which test your doctor offers will depend on your symptoms and medical history. If you have a flexible sigmoidoscopy and your doctor spots any problems, they may recommend you have a colonoscopy afterwards.

  • Polyps are small growths in the lining of your bowel. They’re common and don’t usually cause any symptoms. Most polyps don’t cause any problems but there’s a small chance that some can change into bowel cancer over time, if they’re not removed. If your doctor finds any polyps during your flexible sigmoidoscopy, they usually remove them.

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  • Reviewed by Pippa Coulter, Freelance Health Editor, Bupa Health Content Team, July 2019
    Expert reviewed Ian Arnott, Consultant Gastroenterologist
    Next review due July 2022