CT enema scan - Overview - Preparation with Omnipaque | Guy's and St Thomas' NHS Foundation Trust

Important - only follow these instructions if:

you are taking Omnipaque as preparation before your scan.

You have been asked to take a liquid dye (Omnipaque), which 'tags' poo that is left in your bowel so it can be seen on the CT scan. This is known as faecal tagging.

You should have received your appointment letter and 2 small bottles of Omnipaque.

Omnipaque is a liquid dye that you drink. The liquid dye shows up on the CT scan of your bowel, helping the doctor to read the scan.

Most of the dye is not taken in by the body, and gets mixed with the poo in your large bowel. The dye will eventually be passed out of your body in your poo.

Making changes to your diet

You have also been asked to make some changes to your diet the day before your scan.

You should only have small meals made up of low residue foods before your scan.

This will help the Omnipaque work properly.

Low residue foods

you can eat fats such as butter and margarine, only a small amount of these should be used
you can eat eggs, especially boiled and poached
you can eat cereals such as cornflakes and crisped rice cereal, but not bran
you can eat cream cheese, cottage cheese or cheese sauce
you can eat potatoes without the skin, boiled, creamed, mashed or baked, but not roasted or deep fried (chips)
you can eat plain white pasta, noodles or boiled rice
you can eat meat or fish
you can eat gravy made from stock cubes (white flour or corn flour can be used to thicken)
you can eat white bread or toast
you can eat sugar or sweetener
you can eat clear jelly

Food and drink to avoid

Do not eat vegetables
Do not eat fruit
Do not eat brown bread
Do not eat brown rice
Do not eat brown pasta
Do not eat jam
Do not eat nuts
Do not eat biscuits
Do not eat crisps
Do not drink alcohol

The day before your scan

Follow these instructions on how to prepare and when to take the Omnipaque. There are also examples of what you can eat and drink on the day before your scan.

You can have tea or coffee (with milk and sugar or sweetener, if needed).

You can also have other clear fluids, such as water, clear soups, herbal tea, black tea or coffee, or diluted cordials or fruit juice (smooth with no fruit bits).

Choose one of the following:

30g crisped rice cereal or cornflakes with 100ml of milk
2 slices of white bread or toast, with a small spread of butter or margarine and honey
1 boiled or poached egg, and 1 slice of white toast or bread with a thin spread of butter or margarine
50g of cottage cheese or cream cheese, and one slice of white toast or bread with a thin spread of butter or margarine

Drink 1 bottle of Omnipaque.

You can have tea or coffee (with milk and sugar or sweetener, if needed)

Choose one of the following:

75g meat or fish with gravy
2 boiled or poached eggs
100g cream cheese or cottage cheese

Add one of the following:

2 slices of white bread or toast, with a small spread of butter or margarine
2 egg-sized potatoes without skins, with a small amount of butter or margarine
2 tablespoons of plain white pasta or rice

Drink plenty of clear fluids, preferably water.

Tea and coffee should now only be black (no milk).

Do not have any solid food, milk or other dairy products until after the scan.

Drink the second bottle of Omnipaque at 6pm.

Do not have any solid food.

You can have clear soup, a meat extract drink or clear jelly.

Do not eat any more food until after you have had the scan.

Throughout the day drink plenty of clear fluids so you do not get dehydrated. For example water, squash, fizzy drinks, clear strained soup, clear stock.

As a guide, try to drink about 1 glass every hour (during waking hours).

Signs that you are dehydrated include dizziness, headache and confusion.

People with diabetes or restricted diets for religious or ethical reasons should contact the CT nurse coordinator for dietary advice.

On the day of your CT scan

Read about what happens during and after having your CT scan.

Preparation with Omnipaque