Flexible sigmoidoscopy

Expert reviewer, Dr Alastair McNair, Consultant Gastroenterologist
Next review due November 2024

Flexible sigmoidoscopy is a test to look inside the bottom part of your large bowel. It uses a flexible tube called an endoscope, which has a camera on the end. The procedure can be used to find out the cause of symptoms such as bleeding from your bottom.

Patient talking with a doctor

Why do I need a flexible sigmoidoscopy?

When you have a flexible sigmoidoscopy, a doctor puts a tube with a camera attached into your back passage. They then take pictures or a video of the inside of your bowel.

Your doctor may recommend you have a flexible sigmoidoscopy for several reasons. These include:

  • you have bleeding from your bottom
  • your pooing habits have changed – for example, needing to poo more often or having diarrhoea or constipation
  • removing polyps (small growths in the lining of your bowel) – these growths can sometimes turn into cancer
  • keeping an eye on existing problems in your bowel – for example, ulcerative colitis or Crohn’s disease – to look for any changes
  • checking out bowel cancers before surgery
  • treating volvulus — a condition in which your intestine gets twisted and blocks your bowel

Flexible sigmoidoscopy used to be part of the NHS bowel cancer screening programme in England. This was called bowel scope screening. But bowel scope screening is no longer offered as part of the NHS bowel cancer screening programme.

What are the alternatives to flexible sigmoidoscopy?

Your doctor may suggest the following alternatives to having a flexible sigmoidoscopy. This may depend on your symptoms, age and general health.

  • Colonoscopy is a lot like a flexible sigmoidoscopy, but it’s used to look at the whole of your large bowel, not just the bottom part.
  • CT colonography is also called a virtual colonoscopy. It involves having a CT scan of your large bowel. Gas is gently pumped into your back passage while you have the scan. This stretches your bowel so your radiologist can take detailed pictures.
  • Proctoscopy 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 procedure as an outpatient. This means you can go home on the same day and won’t usually 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 sleepy for some time. If you’ve had a sedative, you won’t be able to drive yourself until the day after your sigmoidoscopy.

Giving your consent

You’ll meet the doctor or nurse carrying out your procedure before you have your surgery. They’ll talk to you about:

  • what will happen when you have the procedure
  • what to expect afterwards
  • if there’s any chance of complications

You should be given time to make sure you understand everything and have a chance 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 and know about the procedure you’re having.

Medicines to stop

You’ll be given clear instructions about how to prepare for your sigmoidoscopy. This may mean you have to stop taking some of your usual medicines before your procedure. If you’re taking medicines that thin your blood – for example, clopidogrel or warfarin – contact the hospital where you’re having the procedure. They’ll tell you what you need to do.

Having an enema

Your bowel needs to be empty of poo before you have a flexible sigmoidoscopy. You’ll usually need to have an enema before the procedure. An enema is a liquid that’s injected into your back passage to flush out your bowel, so your doctor has a clear view inside it. You may be asked to:

  • do the enema yourself at home before you come in for your sigmoidoscopy
  • have the enema at the hospital just before your procedure

After the enema, you can’t eat or drink anything before your procedure. This is to make sure that your bowel stays empty.

Sometimes, you may be asked to take a laxative instead. This will be a liquid that you drink to empty your bowel. If you’re having a laxative, you’ll usually need to follow a special diet for a couple of days before this. Again, you usually can’t eat or drink anything for a few hours before your surgery.

At the hospital

A flexible sigmoidoscopy is usually done in an endoscopy unit at a hospital. When you arrive:

  • a nurse will check your temperature, blood pressure, breathing and heart rate
  • you’ll meet the doctor or nurse carrying out your procedure, so you can 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’s done by a specially trained doctor or nurse.

You don’t usually need to have an anaesthetic or sedative for a flexible sigmoidoscopy. The procedure can be uncomfortable at first, but it doesn’t usually hurt. But you can choose to have a sedative if you want to. A sedative will make you feel more relaxed and a bit sleepy, but you’ll stay awake during the procedure. If you decide to have a sedative, it will be injected 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 check your back passage. They’ll then carefully insert the endoscope (a thin flexible tube), using an oily gel to make it as comfortable as possible.

The doctor or nurse will pass small amounts of gas and water through the endoscope. This will make it easier to see inside your bowel. It may make you feel a bit bloated.

During the procedure, your doctor or nurse will be able to see pictures from the endoscope on a screen. They’ll gently guide the sigmoidoscope through your bowel. They’ll take pictures and look at the lining of your bowel as they go. They’ll also be able to take small samples from the lining of your bowel if they need to. These samples are called biopsies. The doctor or nurse may remove any polyps they find. To do this, they pass special instruments through the endoscope. For more information on this, see our FAQ: What are polyps and why do they need removing? below.

If you find the procedure is really uncomfortable at any time, tell your doctor or nurse and they’ll 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 may 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’ve had a sedative, you’ll be monitored for a couple of hours in the endoscopy unit while you recover. You’ll need to arrange for someone you know to drive you home and stay with you for the rest of the day.

Before you leave the hospital, your doctor or nurse will talk to you about how the procedure went and if 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

Like all types of surgery, flexible sigmoidoscopy can cause some complications. But it’s usually a very safe procedure and complications are rare.

If you’ve had a sedative during the procedure, you’ll be monitored closely. Sedatives can sometimes affect your breathing, blood pressure and heart rate.

Sometimes, the endoscope might damage your bowel during the procedure or cause some other complications.

  • Bleeding. This is most likely if you’ve had polyps removed or had a biopsy. The bleeding usually stops on its own without any treatment. But sometimes, you may need another procedure to treat the problem.
  • A tear in your bowel (bowel perforation). If this happens, doctors may close the tear using small metal clips inside your bowel. But if this isn’t possible, you’ll need an operation to repair the tear.
  • An infection may occur but this is very rare.

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

  • very bad pain in your tummy or bottom
  • heavy bleeding or bleeding that doesn’t stop from your back passage
  • blood in your poo
  • a high temperature or generally feel unwell

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Related information

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  • Reviewed by Victoria Goldman, Freelance Health Editor, November 2021
    Expert reviewer, Dr Alastair McNair, Consultant Gastroenterologist
    Next review due November 2024