This scan allows us to assess the function of the kidneys and to detect any abnormality in the flow of fluids through them and into the bladder. A small amount of radioactivity, known as a “tracer”, is attached to a chemical compound called MAG3 which demonstrates the flow of urine from the kidneys into the bladder.

How does it work?

On arrival, a small needle will be placed into a vein in your arm or hand and you will be asked to lie on the scanner couch. A small amount of the tracer will be injected while you are lying on the couch and images taken as soon as the injection is given, using a gamma camera positioned underneath the couch. A series of images will be taken continuously for 20 minutes and you will be asked to lie very still throughout the scan. As the scanner is positioned under the couch patients find it easy to do this test.

At the end of the scan you will be asked to empty your bladder and another picture will be taken, which should last about one minute. It may be necessary to take a further picture an hour after the test has finished. In some circumstances you may be given a diuretic, a drug that encourages the kidneys to work harder, 15 minutes before the scan.

How do I prepare?

We would like you to drink plenty of fluids before you arrive for the scan and, in some cases, we may ask you to drink extra fluid on your arrival. You may eat and drink normally before the test and continue to take all your usual medication.

After the procedure

Once the scan has finished the doctor will check its quality while you wait and the technologist will then let you go home. The radiation dose from this procedure is very small and there is no need to make any change to your routine.

There are no side effects from the injection; it will not make you feel sleepy or affect your ability to drive.

There are currently no related conditions associated with this test.

Royal Brompton nuclear medicine

Level 3, Chelsea Wing, Sydney Street


Monday to Friday, 9am to 5pm

Tel: 020 7351 8666 / 9
Fax: 020 7351 8668

Patient advice line: 020 7351 8667

If you have any questions or concerns about the scan please call our patient advice line.

It is an answerphone service – leave a message and we will call you back within 24 hours.

Department head

Kshama Wechalekar

Nuclear medicine MAG3 renogram appointment information - Harefield Hospital - February 2014 (pdf, 59.5KB)