Digestive tract preparation

Preparing for a colonoscopy

When we are preparing for a colonoscopy, we alter our diet.

We follow a low fibre diet, followed by a day of having soluble foods and a liquid only diet before taking our bowel prep.

We want to make it as easy as possible for our bodies to digest food so that we can clear our digestive tract; one of the ways we can do this is by avoiding foods which are high in fibre. Fibre is a type of carbohydrate that the body can't digest so it passes through the body undigested.

We need our lower digestive tract to be clear so the endoscopist can completely investigate the lining. By eating a low fibre diet, followed by a day of liquid and soluble foods, we make it easier for the body to digest what we eat and pass any remaining food in our system.

We take bowel prep before our appointment in order to completely clear our digestive systems.

We don’t want our low fibre diet to disrupt our day. To make our pre-procedure preparation as easy as possible, we have asked some of our patients how they prepare for their appointments.

Your personalised pre-procedure information will tell you when you need to move onto the different stages of bowel preparation.

By making small changes to our meals, we can make sure we are doing everything possible to have a successful procedure.

What is a low fibre diet?

This is a diet which contains little or no fibre/roughage. The aim of this diet is to reduce the amount of undigested food that passes into the large bowel.

A low residue diet may help prevent blockages in your bowel by reducing foods that are poorly or partially digested.

Please be aware that very fatty foods, such as fried foods can also be difficult to digest and may cause discomfort if eaten in large quantities. For this reason we suggest that you avoid very fatty foods.

Low fibre diet

Today we can still eat a lot of different foods, but we’ll need to start our low fibre diet and start having smaller meals.

It is important to drink plenty of fluids. Try to drink 2 litres (about 8 to 10 glasses) in a day.

We need to remove raw or cooked fruits and vegetables which are sliced or whole, very fatty foods and foods like brown bread, rice or pasta from our diets; although this may sound restrictive, this still leaves us with a lot of options to choose from.

We often don’t need to change our diets too much, just make little changes.

For example, if we are making a sauce for a curry or pasta, we just need to make sure it is smooth or pureed.  

If we are eating a sandwich or a pizza, we make sure we have white bread and remove any whole or sliced vegetables or fruits.

We can switch out high fibre foods like oats or Weetabix for breakfast cereals made from rice or corn.

If we want to have something like orange juice, make sure we are choosing smooth juice rather than orange juice with pulp. You can drink smoothies provided they are completely blended without bits or fruit or seeds.

Although we cannot have legumes like baked beans, we can have tinned foods like spaghetti hoops or creamed soups.

If you are struggling with the diet, we have made a list of foods which you can eat on a low fibre diet and foods you need to avoid. You can find this list above.

Liquid and soluble diet

Today will be more of a change from our usual routine. We want to stop putting any more food into our digestive systems.

Try to drink 2 litres (about 8 to 10 glasses) in total throughout the day (not including the bowel preparation solution).

You can drink tea or coffee with a small splash of milk. Do not drink alcohol.

We can still have soluble foods like boiled sweets and jelly.

For savoury flavours we can have vegetable, chicken or beef broths, clear strained soups and clear stocks.

We can have drinks like squash, fizzy drinks, sports drinks, lemonade, apple juice.

It is important to keep drinking water and include sugar and salt in our diet today.

Nil by mouth

About 24 hours before our procedure, we need to start taking bowel prep laxatives.

The solutions taste better if they are served chilled. If you are struggling to drink the solution, you may want to mix it with squash and drink through a straw.

You may want to mix the solutions in advance and keep them in the fridge. You need to use them within 24 hours of being prepared.

It is very important to drink all of the solution and continue to drink water. You should aim to drink one glass for every hour you are awake.

Going to the bathroom

You need to stay near a toilet when you start taking the bowel preparation solution.

You can expect to poo frequently and have diarrhoea (watery poo). This starts within 3 hours of taking the first amount (dose) and continues until after your last dose.

We plan when you take the bowel preparation solution carefully. This means that the effects wear off before you are due to travel to the hospital.

Side effects of bowel preparation

It is common to have some bloating (when your tummy feels full and uncomfortable) or stomach cramps.

You can use a barrier cream (a cream to protect the skin from damage or infection), such as zinc and castor oil, on your bottom. This can prevent soreness during your frequent trips to the toilet.

Keep drinking clear fluids to stop yourself from getting dehydrated. As a guide, try to drink about 1 glass every hour. Signs that you are dehydrated include dizziness, headache and confusion.

Please report any allergic reactions, such as a rash, itchiness or redness, to the endoscopy unit or your GP.