Micturating cystourethrogram (MCUG) factsheet


A micturating cystourethrogram (MCUG) is a test used to take clear X-ray pictures of your child’s urinary system. 

The urinary system includes the:

  • kidneys – the organs that filter waste from the blood, turning it into urine
  • ureters – thin tubes that connect the kidneys to the bladder
  • bladder – where urine is stored
  • urethra – the tube that takes urine out of the body

The MCUG uses a special radiopaque liquid called contrast. Radiopaque means it can absorb X-rays. When the contrast moves through your child’s urinary system, it absorbs the X-rays and will appear white on the images.

Before the test

Your child's treating team will let you know if there are any special instructions to follow for the test. This can include taking antibiotics before and after the test to make sure your child does not develop an infection.

You will also need to let the hospital know if your child: 

If your child has a heart condition, you will need to let their specialist doctor know about the MCUG so they can make sure you have the right antibiotics.

Always speak to your child's treating team if you are unsure what your child needs to do to prepare. 

During the MCUG, your child will need to do a wee. Children can be anxious about doing a wee in front of others, especially if they are toilet trained.

If your child is very anxious or stressed, you can speak to the doctor about nitrous oxide therapy to help them relax.

Parents and carers are also encouraged to be with their child during the test for support. You will not be able to be in the room during the test if you are pregnant, because of the X-rays. 

 During the test

The MCUG will happen in the hospital's Medical Imaging Department. This is where different types of X-rays and scans are done.

In the MCUG, photos will be taken as your child's bladder is filled with contrast and again when they empty it. In some cases, your child may need to repeat the filling up and emptying of their bladder to make sure the right photos have been taken.

The general steps of the MCUG are broken down into two parts.

Part 1: Filling the bladder

  1. your child will lie down on an x-ray table with a large camera above it
  2. the doctor will wipe the area around your child's penis or vulva with an antiseptic to make sure there are no germs
  3. a numbing gel is put on the end of a small plastic tube, also known as a catheter
  4. sometimes, the doctor might also give your child an injection of anaesthetic to numb the area
  5. the tip of the catheter is pushed through the urethra, found at the tip of the penis or just above the opening of the vagina
  6. the other end of the catheter is connected to a bag of contrast liquid, hung up next to the table
  7. once the tube is connected, the liquid will flow into your child's bladder 
  8. photos of the full bladder will be taken using the X-ray camera above the table.

Part 2: Emptying the bladder

  1. your child will stay on the x-ray table, and will have a special nappy, blue sheet, bedpan or urine bottle to collect their urine
  2. your child will be asked to empty their bladder, or do a wee
  3. photos of your child's urinary system will be taken using the x-ray camera above the table as they do a wee
  4. when the bladder is empty, the tube is taken out, and the test is finished.

 After the test

Your child’s doctor will check the images taken after the test and book a follow-up appointment to discuss the results with you.

Your child will need to drink plenty of fluid for 24 hours after the MCUG to make sure all the contrast liquid is gone from the bladder.

They may be a little sore, and there may be some blood in their urine for about 24 hours after the test. This is normal.

See your local doctor or present to your nearest emergency department if your child:

  • develops a fever
  • had urine in their blood for longer than 24 hours
  • passes any clots of blood in their urine.


Nitrous oxide therapy

Nitrous oxide is a gas that is given to people who are having painful or stressful procedures but need to stay awake. It is also called happy or laughing gas.

Nitrous oxide slows down the signals between the brain and the body, helping your child to feel calm and relaxed.

Children who are very anxious or distressed may be able to use nitrous oxide therapy to help them relax enough to urinate during the test. 

You will need to speak to your child’s doctor about nitrous oxide therapy before the test to make sure the treatment is suitable. Your child will need to stop eating and drinking at least two hours before having the nitrous oxide gas. 

Last updated Friday 19th January 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024