A computerised tomography scan (CT scan) is a type of imaging test – a test that uses special equipment to create detailed images of the inside of the body, including organs like the kidneys.

What is a computerised tomography (CT) scan?

A CT scan is a special kind of X-ray test. X-rays pass through fluid (liquid) and soft tissues but are blocked by more dense – or more solid – structures such as bones.

A CT scan uses several X-rays, which are sent at different angles at the same time. These images can build up a detailed picture of parts of the inside of your child’s body, including bones, organs and liquids.

A renal CT scan looks closely at the kidneys and surrounding areas. A liquid called contrast dye may be used to highlight the areas more clearly.

Why does my child need this test?

Your child’s doctor may recommend a CT scan when more information is needed to make a diagnosis. Your child may already have had either an X-ray test or an ultrasound scan, but these may not have provided enough detail.

Are CT scans safe?

CT scans are generally safe, but they expose your child to a higher dose of radiation than other imaging tests. We’re all exposed to low levels of radiation every day – it comes from sources including building materials and some foods.

When your child has a CT scan, they receive the amount of radiation they’d be exposed to naturally in around 9 months to 3 years.

It’s possible that exposure to higher levels may be linked to a raised risk of cancer later in life. However, the benefits of having a CT scan to help diagnosis are usually much greater than any potential risk.

Where will it take place?

CT scans are usually carried out in the hospital imaging department.

Who will perform the CT scan?

A radiographer, a healthcare professional specialising in imaging tests, performs the scan.

How to prepare your child for a CT scan

Your child does not usually need to do anything to prepare for this test, but your doctor will let you know.

Talk to your child about the scan and what will happen. If they are old enough, explain what the scan is looking for and why it is needed.

Some children find it uncomfortable to be inside the scanner. The machine also makes a whirring sound. If your child is worried, speak with your doctor. Your child may be able to meet with a play specialist, who can use dolls and other toys to help them prepare for the test.

You may be able to stay with your child during the test, but you will need to wear a lead apron to help minimise your exposure to radiation.

Older girls may be asked if they are having their periods and about the dates of their last menstrual period. They may also be asked if they are pregnant or if they could be pregnant. This is because ionising radiation from CT scans may harm an unborn baby.

What happens during the scan?

If a contrast dye is used, this is injected into a blood vessel, using a needle or a small plastic tube called a cannula. This is usually in the hand, arm or foot. Your child may feel a sharp scratch from the needle. A local anaesthetic, a spray or cream, can be put on your child’s skin before inserting the needle or cannula, to make the area feel numb. When the dye is injected your child may feel a brief warm flush or the feeling that they have passed urine. They may also notice a metallic taste in their mouth. This feeling usually goes away quickly.

Your child will lie on a bed inside the CT scanner, a large, round machine with a tunnel. Some people say that it looks like a very large doughnut.

The bed moves slowly back and forward in the tunnel while the scanner beams X-rays into your child’s body at different angles, to build up a detailed picture.

Your child needs to lie still during the procedure.

The radiographer can talk with your child during the scan. They may ask to hold their breath at certain times to get clear images.

The scan does not hurt, and takes only a few minutes.

What to expect afterwards

Your child can usually go home straight away after the scan. The cannula will be removed before you leave.

Getting the results

The images are sent to a specialist imaging doctor called a radiologist, who reviews them and explains the findings in a report that gets sent to your doctor. Speak with your doctor about when you should expect the results.

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