Everything you need to know about having a colonoscopy

Regardless of whether you have inflammatory bowel disease (IBD), you should be given a full colonoscopy with biopsies to check for IBD once you are diagnosed with PSC.

A colonoscopy is an examination of your large bowel (colon). If you already have IBD, you will have a colonoscopy to commence regular surveillance for potential cancer in your colon.


Have you had a colonoscopy? (Answer only if you have a PSC diagnosis)

What happens in a colonoscopy?

Colonoscopy preparation

Before you have a colonoscopy, you need to prepare by having a ‘bowel prep’. Colonoscopy bowel prep, varies from hospital to hospital. It is important to carefully read any dietary guidance you are given and ask about anything you don’t understand well before the procedure date.

Do I need to time off work for a colonoscopy?

It depends on the timing of your bowel prep and colonoscopy. Some people work a half or full-day on the day of the bowel prep. After the colonoscopy you may feel quite groggy, so even if you have the colonoscopy in the morning, you may not feel up to working until the next day. If you have sedation for the colonoscopy, you will not be able to drive for at least 24 hours.

Types of bowel prep

There are a number of different bowel preps, which differ in taste and volume. If you’ve been given a bowel prep in the past that you found difficult to take, make sure that prior to your colonoscopy, you ask if there is an alternative preparation you can take. If the bowel prep you want to have is not one the hospital usually uses, you will need to justify your request, but most hospitals are understanding, especially if you explain you have regular colonoscopies as a PSC patient.

Bowel prep instructions

Pay careful attention to the instructions you have been given because protocol varies from hospital to hospital. If you lose your instructions search on your hospital’s website, as they are often included in the information about the hospital services, or phone the endoscopy unit for advice. It is vital to follow the instructions to the letter, and to finish all of the bowel prep. This is critical because the doctor needs a clear view of the sides of your colon to look for any abnormalities. There will not be a clear view if you haven’t taken your bowel prep properly.

The pre-colonoscopy diet: low residue foods

You may be asked to follow a special ‘low residue’ diet for a few days before your colonoscopy. The low residue diet consists of food that doesn’t form large stools. Check out our list of low residue foods.

The pre-colonoscopy diet: clear fluids

You’ll be told to move onto a clear liquid diet for the last day. The clear liquid diet allows more than just water, so don’t be fooled by the word ‘clear’. Check out our ideas for allowable clear liquids. There are more than you’d expect!

Drinking the bowel prep

The day before your colonoscopy (and sometimes on the day itself), you will drink some ‘bowel preparation’ (bowel prep). This is a special drink that is designed to completely clear out your bowels (by giving you severe diarrhoea).

Tips on drinking bowel prep

  • You don’t have to mix your bowel prep with water. You can mix it with something that has a strong flavour to hide the bowel prep taste, such as orange squash. Make sure that this mixer isn’t red or purple!
  • Put the prep in the fridge or freezer. It is easier to drink when it is chilled. You could even put it in the freezer to eat like a slushy later!
  • Use a straw to drink the prep.
  • Have a chaser: follow each mouthful of prep with a strongly flavoured drink (that isn’t purple or red). Be mindful that you will associate that chaser with bowel prep forever more, so the chaser should never be your favourite drink!

How long does bowel prep take to work?

It can vary from a couple of hours to eight hours before you see the effects of the bowel prep. Stay close to the toilet, because when it works, it works! Wear loose-fitting clothes. You’ll be on and off the toilet for a few hours so have everything you need close to hand, including things to keep you occupied, like a book or a fully-charged tablet.

Wet wipes are your friend!

The whole point of a bowel prep is to clear your bowels by making you poo a lot. To keep your skin from becoming irritated from all the wiping that you’ll need to do, apply petroleum jelly to protect the anus area and use soft toilet paper or unscented wet wipes. Pat dry afterwards.

The colonoscopy procedure

  • Sedation: you will be offered sedation and painkillers for the procedure and you may or may not be aware of what is going on. Some hospitals also offer gas and air throughout the procedure.
  • The camerawork: you will lie on your left side while a flexible instrument called a colonoscope (endoscope) is inserted through your rectum into the bowel. The scope shines light onto the lining of your bowel and pictures are taken which are transmitted to a screen; you may be able to view these.  Some small tissue samples should be taken (biopsies). You can sometimes feel a slight tugging sensation as the biopsies are taken. Air is pumped into the colon to inflate it, to allow the doctor to view the colon walls. This can sometimes be uncomfortable if insufficient air is taken out before getting the scope round a bend in your colon.
  • Moving about: throughout the procedure you may be asked to move onto your back and side. This is so the doctor can access the twists and turns in your colon, causing you as little discomfort as possible. The nurses help you manoeuvre round as it can by quite tricky when drowsy and attached to a tube!
  • Spray dye: sometimes a dye is used during the colonoscopy to improve the contrast and facilitate the identification of abnormal cells. This is called chromoendoscopy.

Sister Kay Greveson Royal Free on colonoscopies (video)

Note that the video suggests mixing the prep with blackcurrant cordial. We do NOT recommend mixing with any liquid that is red or purple.

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