Nuclear Medicine Renal Scan

Authors: Dr Chian Chang* Dr Dee Nandurkar *

What is a nuclear medicine renal (kidney) scan?

In a nuclear medicine renal scan, images, or pictures, are taken of fluid going into the kidneys through the bloodstream, the filtered wastes from the blood in the kidneys and the flow or drainage of the waste into the bladder through the ureters (that join the kidneys to the bladder).

A nuclear medicine renal scan uses radiopharmaceuticals (radioactive medications) injected into a vein, usually in the arm, to provide clear images of the kidneys taken with a special camera called a gamma camera. The scan can be carried out using one of two different radiopharmaceuticals – DTPA (diethylene triamine pentaacetic acid) or MAG3 (mercaptoacetyletriglycine). They are similar medications, but MAG3 gives significantly clearer images in some patients, particularly very young children and those patients with poor kidney function.

Why would my doctor refer me to have this procedure?

Your doctor will refer you for a nuclear medicine renal scan to look at the blood supply, function and flow of urine from the kidneys if it is suspected that there are problems with how your kidneys are working. Reduced kidney function may be shown in abnormal blood tests, high blood pressure or abnormal results obtained from the urine itself.

How do I prepare for a renal scan?

It is important before having the scan that you drink plenty of fluids, so the gamma camera can take images of the fluid as it is collected in the kidneys and discharged through the ureters and into the bladder. If the scan is being carried out because of high blood pressure secondary to kidney disease or a narrowed renal artery, some blood pressure medications should be stopped 4–7 days before having the scan. There is usually no need to fast, but if the scan is for the investigation of high blood pressure, some institutions may require you to fast for up to 4 hours before the scan. Please discuss this at the time of your booking.
Speak to your doctor or contact the nuclear medicine department of the hospital or radiology facility where you are having the scan for instructions about preparation for the scan.

If you may be pregnant or are breast-feeding, you must tell your doctor or specialist and the nuclear medicine staff where you are having the scan. If you are breast-feeding, your doctor and the nuclear medicine staff will discuss the need to express breast milk, and reduce direct contact with your baby for a short time after the scan, this is to avoid unnecessary radiation to your child. Some pharmaceuticals that are used in nuclear medicine studies can pass into a mother’s breast milk and subsequently to the child.

What happens during a renal scan?

On arrival, your height and weight will be measured so the nuclear medicine technologist can determine the dose and camera set-up. To ensure you are well hydrated, you will be offered some water to drink, as noted in the ‘How to prepare for a renal (kidney) scan?’ section above .

For both the DTPA and MAG3 scans, you will lie on the scanning bed with a gamma camera located under the bed. It is important to keep still during the scanning, as movement will blur the images. Let the nuclear medicine technologist know if this could be a problem for you and they will assist you.

A cannula (thin plastic tube) will be inserted into your vein, usually in the arm, and remain there during the scan. The radiopharmaceutical is given through the cannula. The gamma camera will sit over your body, but will not touch you. Images of your kidneys will be taken continuously for about 20 minutes. Depending on the radiology facility where you are having the scan and the reason you have been referred for the scan, additional medication may be given through the cannula. Common additional medications used include frusemide (Lasix) and captopril to make the kidneys work harder and make any obstruction easier to see on the images.

At the end of the scan, you may be asked to go to the toilet and empty your bladder, then return for a further 2 minutes of imaging. The cannula is removed before you leave the hospital, nuclear medicine department or radiology facility.

Are there any after effects of a renal scan?

If a dose of a frusemide or captopril is given, you may need to empty your bladder more often than usual for that day. It is important you drink plenty of fluids after having the scan to avoid dehydration. Some people have profound low blood pressure after captopril. Please let the staff of the facility where you are having the scan know if you feel dizzy, light headed or unwell.

How long does a renal scan take?

The test itself will take approximately 30–60 minutes. The time varies because the rate at which the kidneys function will differ for each individual.

What are the risks of a renal scan?

There are no known associated risks involved in the DTPA or MAG3 scan itself.

The test involves ionising radiation, which is relatively small and similar to many other routine medical imaging tests. For more detailed information (see InsideRadiology: Radiation risk of medical imaging for adults and children). As with any medications, there is a small chance of an allergic or adverse reaction. Please discuss this with your doctor or with the nuclear medicine staff carrying out the scan if you have any concerns.

What are the benefits of a renal scan?

This test provides information on the blood supply, function and flow of urine from the kidneys.

A DTPA or MAG3 scan can help your doctor assess individually how each of your kidneys is working and to look for a cause of high blood pressure or other abnormal test result.

Who does the renal scan?

A nuclear medicine technologist will give the injection, carry out the scan and process the images. A nuclear medicine specialist (specialist doctor) will review the images along with your medical history and provide a report for your referring doctor. See Nuclear Medicine for more details about these health professionals.

Where is a renal scan done?

A DTPA or MAG3 scan is carried out in a nuclear medicine department either in a hospital or a private radiology facility.

When can I expect the results of my renal scan?

The time it takes for your doctor to receive a written report will vary. Let the staff where you are having the scan know if you require your results urgently.

It is important that you discuss the results with your doctor, either in person or on the telephone, so that they can explain what the results mean for you.

*The author has no conflict of interest with this topic.

Page last modified on 24/8/2018.