MAG3 renogram scan

A MAG3 renogram scan checks the function of the urinary system (kidney, ureters and bladder). It checks the drainage of pee (urine) from the kidneys to the bladder, to identify any obstruction or delayed drainage.

The results of this scan give your doctors more information about your condition, and help them to plan your treatment.

MAG3 renogram scans are done in the nuclear medicine department, using a gamma camera.

Preparing for a MAG3 renogram scan

You can eat, drink and take any medicines as normal.

You will need to drink 1 litre of fluid before arriving for your scan, but you can pee (empty your bladder) when you want to. If you are on restricted fluids (for example, due to a medical condition) please let us know before your appointment.

You should be prepared to be at the hospital for 1 to 2 hours.

During a MAG3 renogram scan

You will meet our team of technologists or radiographers and they will explain the procedure to you. You can ask any questions about the scan.

Before your scan we will place a small plastic tube (cannula) into a vein in your arm or hand. We will give you an injection of furosemide 15 minutes before your scan. Furosemide is a diuretic, which is a medicine that removes salt and water from your body. You will be asked to drink water during this waiting period.

Just before the scan, we will ask you to pee to empty your bladder, and then we will take you to the camera room. You will be asked to remove any metal items, such as mobile phones, wallets or belts.

You will lie down on a bed and the camera will be under your tummy (abdomen), or above if you’ve had a transplant. We will ask you to lie still, with your arms by your side, for about 20 minutes, and you can breathe normally.

When we start the scan, you will be given an injection of tracer, which travels through your blood and into your kidneys. The tracer is a radioactive fluid and helps us to see your scans clearly. It is given through your cannula.

After this set of scans, we will take a 1-minute image before and after you have emptied your bladder again. In total, the scanning can take 30 to 45 minutes. We might do some delayed imaging. This means that we might take some more images after waiting for a short time.

Pregnancy and breastfeeding

As the scan involves an injection of a radioactive tracer, you must tell us if you are, or think that you might be, pregnant, or are breastfeeding. If possible, please tell us as soon as you receive your appointment.

For all nuclear medicine tests we check your pregnancy status with you before using any radioactive tracer.

Pain during a MAG3 scan

Inserting the cannula might be painful for a moment, but this soon disappears.

After a MAG3 renogram scan

After this scan you can carry on with your normal activities.

You might need to use the toilet more often after the scan, due to the diuretic. This is perfectly normal and the effects should wear off within a few hours.

After the scan you will still have some radioactivity left in your body. For the rest of the day, avoid any non-essential prolonged, close contact with children, and anyone who might be pregnant. This is to reduce the amount of unnecessary radiation to babies and children.

Risks of a MAG3 renogram scan

We feel that the potential benefits of the scan outweigh the very small risks. We make sure the amount of radiation you receive is as small as possible.

You can read government information about radiation exposure from medical imaging.

It is perfectly safe for you to travel abroad after your scan, but many airports and sea ports are now equipped with very sensitive radiation detectors. It is possible that the very small amount of radioactivity left in your body could set off a detector as you pass through security. If you plan to travel abroad in the week after your scan, it could be helpful to take your appointment letter with you.

Follow-up appointments

If you already have an appointment booked in clinic to discuss the results of the test, please let our team know.

Your images will be reviewed by our doctors and a report will be sent to the doctor that referred you. You will get your results from them.

Resource number: 5367/VER1
Last reviewed: July 2023
Next review due: July 2026

Trusted Information Creator. Patient Information Forum

Contact us

If you have any questions about your test in the nuclear medicine department, please contact us

Phone 020 7188 4112, Monday to Friday, 9am to 5pm

Email [email protected]

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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