MAG3 renal scan factsheet


A MAG3 renal scan is a test used to assess the function of the kidneys.

A MAG3 renal scan is needed to help:

  • determine renal function
  • assess blockages within the renal system
  • detect and assess hydronephrosis (when a kidney swells and can't get rid of pee (urine) like it should)
  • assess success of renal transplant.

This factsheet is for educational purposes only. For further information regarding this topic, please the medical team at your treating hospital.

 Before the test

Explain the test to your child

Explain to your child why the test is needed and reassure them that you’ll be with them every step of the procedure.

Bring toys or comfort items

Bring along their favourite toy, movie or object that provides them comfort (blanket, teddy, dummy etc.).

Numbing cream

If you would like numbing cream put on your child before the cannula is inserted, please arrive 30 minutes prior to your scheduled appointment.

Please discuss this with us before coming in for the scan. 


 During the test

It will take around two and a half hours from arrival to complete the test. 

You will be able to stay with your child throughout the imaging procedure. Your child will be able to watch TV shows, a movie or listen to music while the images are taken. 

Cannula insertion

On arrival your child will have a cannula (a small plastic tube that goes into a vein) inserted. We will run some fluids through it for 20 minutes to ensure that your child is very well hydrated before we start the scan. 

In some cases, it may also be necessary for the physician to insert a bladder catheter, to ensure that the bladder stays empty during the entire procedure. This will be discussed with you and your referring doctor prior to the test.

First scan (20 minutes)

  • In our scanning room, your child will lay on our scanning bed and may be wrapped in a blanket with Velcro seatbelts to help them keep still as movement can ruin the images
  • Your child will be given an radiotracer injection, through the cannula. This injection gives off a small amount of radiation that can be detected by our cameras
  • We only inject a small amount of this radiotracer; the dose we give is based on your child’s weight
  • The injection is given while your child is laying on the scanning bed so that we can make an image of the radiotracer’s journey from the blood stream to the kidneys
  • The kidneys will take it up, process it and turn it into urine. Then we observe whether the urine goes down to the bladder or if it stays in the kidneys
  • This process will take around 20 minutes.

Second scan (20 minutes)

  • If it is necessary, we may give a medicine called Lasix through the cannula and do another scan for another 20 minutes
  • Lasix is a special medicine that makes the kidneys produce more urine than they usually do
  • At the end of the scan, we need to take one last picture after your child empties their bladder.

Will my child feel anything during the MAG3 scan?

Your child may experience some discomfort when the small intravenous cannula is inserted. We can minimise this with the application of numbing cream thirty minutes prior to your appointment.

If Child Life Therapy services are available, they may be able to help distract your child whilst they have their injection.

During the scans, your child will not feel anything. The camera does come quite close but will not touch your child at all.

Is the MAG3 scan safe?

During this procedure your child will be exposed to a small amount of radiation.

The benefits of finding an injury or disease are generally much more important than the potential risk from receiving a small dose of radiation.

Allergic reactions are very rare and almost always mild. Your treating doctor should discuss these with you prior to your scan.

 After the test

Once the images have been taken and checked by a doctor, you are free to go.

Your results will not be given to you directly after the test. The results take time for the Nuclear Medicine team to analyse and report findings. 

Your referring doctor will usually receive the report the next business day. You need to ensure you have a follow up appointment with them to get the results and find out what needs to happen next.

Last updated Tuesday 18th June 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

This factsheet was produced with support from John Hunter Children's Hospital.