Renal Scan and GFR

What is a renal scan and GFR?

A renal scan and GFR (glomerular filtration rate) is a test to look at how well the kidneys filter blood.

How is the test done?

The test is done by a technician called a nuclear medicine technologist. It has four parts.

  1. Your child will be given a small injection (needle) into a vein in the arm or back of hand. The injection contains a very small amount of radioactive medicine that mixes with the blood.

  2. Your child will then lie down on a narrow bed and a special camera will take pictures for 30 minutes right after the injection. This is to see how your child’s kidneys filter the medicine. In most cases your child can watch a movie as the scan is being done.

  3. The technologist will take a blood sample 1.5 hours after the injection.

  4. The technologist will take another blood sample 2.5 hours after the injection. 

Your child can leave the department between the scan and the blood samples, but they must return at the time given by the technologist. 

How long does the test take?

The test can take about three hours in total. This includes the time to inject your child, take pictures of their kidneys, and wait for the blood samples to be taken.

A special cream (called a topic anesthetic) can be put on your child’s skin to numb their hand or arm before the injection. If you would like this option, please arrive at least 30 minutes before your appointment time.

Does my child need to do anything special to prepare for the test?

Your child can eat and drink as usual, but they may be asked to drink one or two glasses of water or juice before the test so they are well hydrated. 

Some children need a blood or urine test before the test. Your doctor’s office will tell you if your child needs one. The test can be done in the Ambulatory Centre on the main floor near Shoppers Drug Mart, but it must be done before the renal scan and GFR. Please arrive early to leave enough time for the test and still be on time for the GFR scan. 

Will I be able to stay with my child during the test?

One parent or guardian may stay in the room with the child, but no other children are allowed. This is to make sure the test is done properly.

When are the results available?

A doctor from the nuclear medicine team will send a report to your family doctor within one or two working days of the test. Please contact your family doctor to get the results. You will not be able to get the results from the nuclear medicine technologist.

How do I contact the hospital about the scan?

If you have any questions or if you need to change your appointment, please call the Nuclear Medicine Department, The Hospital for Sick Children, at 416-813-6065.​