Renal MAG3 Scan

What is a MAG3 renal (kidney) scan?

A MAG3 renal scan tells your healthcare provider how well your kidneys work. It’s a type of nuclear medicine imaging test. That means a provider injects a very small amount of radioactive substance (called a tracer or radiotracer) before taking pictures of your kidneys with a gamma camera.

Providers may use renal MAG3 scans to check:

• Your overall kidney function.
• Whether you have blockages in your urinary system.
• Drainage of pee from your kidneys to your bladder.
• Blood flow to your kidneys.
• Assessment for kidney transplants.

Providers also use MAG3 scans to diagnose conditions like:

• Hydronephrosis.
• Acute tubular necrosis.
• Renal artery stenosis.

MAG3 vs. DTPA renal (kidney) scans

There are different types of kidney scans, and providers use various radiopharmaceuticals (radiotracers) depending on the need. Diethylene triamine pentaacetic acid (DTPA) is a common radiotracer used for kidney imaging. But it doesn’t always produce clear images in certain people, particularly children and individuals with poor kidney function.

The name “MAG3” comes from the chemical “mercaptoacetyltriglycine” — the radioactive tracer used during a MAG3 scan. Mercaptoacetyltriglycine produces clearer images than DTPA in certain people. That’s why MAG3 scans are more common in children than adults.

How does a MAG3 renal scan work?

A MAG3 renal scan uses a radiotracer to highlight certain areas of your urinary system. Before your test, a provider will inject a small amount of the radiotracer into a vein. Once injected, it:

• Travels through your bloodstream.
• Passes through your kidneys.
• Collects in your bladder.

The radiotracer emits gamma rays, and the gamma camera detects these rays. As the radiotracer moves through your urinary system, it shows your provider how your kidneys, ureters and bladder work in real-time.

Preparing for a MAG3 renal scan

Generally, a MAG3 kidney scan doesn’t require special preparation. You can eat and drink normally and take all medications as usual unless your provider tells you otherwise.

If your child is having a MAG3 scan, give them a simple explanation of why they need the test and what they can expect. Young children may wish to bring books or stuffed animals with them. Many healthcare facilities also let children choose a movie to watch. You can stay with your child during the entire procedure.

Be sure to let the healthcare provider know if you’re pregnant. They’ll give you guidelines to minimize unnecessary radiation exposure.

What to expect during the test

When you arrive for your MAG3 renal scan, your provider will:

1. Ask you to go pee so you can empty your bladder. (In children, a healthcare provider will place a catheter to do this.)
2. Ask you to lie down on an exam chair or table.
3. Place an IV catheter in a vein (usually in your arm).
4. Inject the radiotracer (MAG3) into the IV line.
5. Begin taking pictures with the gamma camera. (This step usually takes 20 to 40 minutes. You’ll need to remain very still until your provider finishes taking pictures.)
6. Ask you to pee and empty your bladder again.
7. Take a final picture with the gamma camera.

In some cases, they may also inject a diuretic (a medication that makes you pee more for a short time) and then take pictures with the gamma camera while you pee. They might do this on a toilet with an imaging setup. Or if you need to stay on the exam table, they may give you a bedpan to pee in. Your healthcare provider can tell you what to expect if your test involves this step.

From start to finish, a MAG3 renal scan usually takes one to two hours.

What to expect after the test

After your test, a radiologic technologist will check the images for quality. You’ll be able to return to normal activities immediately following your scan.

What are the risks of a MAG3 scan?

“Radioactive tracer” may sound scary, but the MAG3 test is generally safe. It uses a very small amount of radiation. The radiotracer becomes inactive within hours of the test and will eventually exit your body through your pee.

When should I know the results of my MAG3 renal scan?

You should know your results within two to three days. If your case is time-sensitive, you may receive your results immediately after your scan.

A radiologist will review your scan, along with your health history and any prior imaging tests. They’ll send a report to your referring provider, who will review your results and then go over them with you.

Is a MAG3 scan painful?

A MAG3 renal scan isn’t painful. The gamma camera will move around your body, but it won’t touch you.

You might have mild discomfort during your IV placement. After your scan, your injection sight might be sore or bruised.

Is a MAG3 scan safe?

A MAG3 kidney scan is very low risk. The gamma camera doesn’t emit any radiation, and the radioactivity in the radiotracer is minimal. Radiotracers are safe for infants, children and adults when given properly in low doses.