Renal MAG3 scan
Informed by recognized medical guidance
Overview
A MAG3 scan is a special type of kidney scan that uses a tiny amount of a safe radioactive substance (called a tracer) to take pictures of your kidneys. It shows how well your kidneys are filtering blood and how urine drains out of them.
Key facts
- The scan is painless and usually takes about 30 to 60 minutes.
- The tracer is injected into a vein and does not stay in your body long.
- Your doctor may order a MAG3 scan to check for blockages, measure kidney function, or follow up after a kidney transplant.
This scan is a fairly common and safe test used when doctors need detailed information about kidney function and drainage.
It is used for people of all ages who have signs of kidney problems, such as swelling, high blood pressure, or repeated urinary infections.
Symptoms
- You are unable to pass any urine for 8 hours or more
- Sudden, severe pain in your side or back that does not stop
- Vomiting and unable to keep fluids down
- You feel confused or very drowsy
- ⚠Blood in your urine that is not from an injury
- ⚠Symptoms of a kidney infection such as fever, chills, and pain
- ⚠Rapid swelling in your legs, feet, or face
Common symptoms
- Swelling in the legs, ankles, or feet (oedema)
- High blood pressure that is hard to control
- Repeated urinary tract infections
- Pain in the side or lower back (flank pain)
- Abnormal results from a blood or urine test
Symptoms in children
- Poor growth or failure to thrive
- Frequent fevers without a clear cause
- Urinary tract infections, especially before age 2
- Visible swelling in the belly (from a blocked kidney)
Symptoms in older adults
- Sudden decline in kidney function, often from dehydration or medication
- Confusion or drowsiness linked to kidney problems
- Swelling that does not go away
- Less urine output than usual
Causes
Main causes
- Blockage in the urinary tract, such as from a kidney stone or narrowing of the tube from kidney to bladder (ureter)
- Reduced blood flow to one or both kidneys
- Scarring of kidney tissue from past infections or disease
- Problems after a kidney transplant, like rejection or poor blood supply
Risk factors
- A history of kidney stones or urinary infections
- High blood pressure or diabetes that affects kidneys
- Having had a kidney transplant
- Birth defects of the urinary system
- Certain medications that can harm kidney function
When to see a doctor
See a doctor urgently if:
- You have severe pain in your side or belly that comes on suddenly
- You notice you are passing very little urine or none at all
- You have a high fever with shaking chills and pain in your back
Book a routine appointment if:
- You have been told by your doctor that a kidney function test is abnormal
- You have mild but ongoing symptoms like leg swelling or high blood pressure
- Your child has had several urinary tract infections in a short time
Diagnosis
The MAG3 scan is used to diagnose problems with kidney function and drainage. It is often done after other tests like blood tests or an ultrasound suggest an issue.
Tests that may be done
- MAG3 scan – pictures are taken right after the tracer is injected and again 20–30 minutes later
- Sometimes you may be given a diuretic (a medicine that makes you urinate) during the scan to see how your kidneys drain
- A blood test to check creatinine and eGFR (estimated kidney function)
- An ultrasound of your kidneys and bladder before or after the scan
What to expect at your appointment
You will lie on a table while a special camera takes pictures. You need to hold still for a few minutes at a time. The tracer is injected into a vein in your arm. After the scan, you can go home and drink plenty of fluids to flush the tracer out.
Treatment
The MAG3 scan itself does not treat anything. Your treatment will depend on what the scan finds. For example, if a blockage is found, you may need a procedure to remove it. If kidney function is reduced, your doctor will help you manage it with lifestyle changes and medicines.
Self-care at home
- Drink enough water each day (unless your doctor says otherwise)
- Follow a low-salt diet to help control blood pressure
- Take any prescribed medicines exactly as directed
- Avoid non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen unless your doctor approves
Medical treatments
Treatments for kidney problems found by the scan may include medicines to lower blood pressure or to help remove extra fluid from the body. If you have a blockage, a doctor might use a small tube (stent) to open the passage. These treatments are always personalised by your healthcare team.
When is surgery considered?
Surgery may be needed if a serious blockage, a large kidney stone, or a structural problem is found. For example, a surgeon may remove a stone or repair a narrowed ureter. Your doctor will discuss the options and risks with you.
Living with this condition
After your scan, you can return to normal activities right away. If a kidney condition is diagnosed, you will need regular check-ups and possibly repeat scans to monitor your kidneys. Many people manage chronic kidney issues well with diet, medication, and follow-up care.
Lifestyle tips
- Stay physically active as recommended by your doctor
- Keep your blood pressure and blood sugar in a healthy range
- Avoid smoking and limit alcohol
- Take all kidney-related medicines consistently
Diet and exercise
A kidney-friendly diet is often low in salt, processed foods, and red meat. Your doctor or a dietitian can give you specific advice. Gentle exercise like walking for 30 minutes most days is safe and helpful for overall health.
Mental health and emotional wellbeing
Waiting for scan results or adjusting to a kidney condition can feel stressful. It is normal to feel anxious or worried. Talk to your doctor or a counsellor about your feelings. You are not alone.
Prevention
You cannot always prevent kidney problems, but you can reduce your risk by keeping your blood pressure and blood sugar under control, staying hydrated, and avoiding medicines that can harm your kidneys. Regular check-ups help catch problems early.
Vaccines
There are no vaccines for kidney disease. However, staying up to date with flu and pneumonia vaccines is important because infections can worsen kidney function.
Screening programmes
Routine screening is not needed for everyone. Your doctor may suggest a MAG3 scan or other kidney tests if you have high blood pressure, diabetes, a family history of kidney disease, or symptoms of a kidney problem.
Complications
If left untreated
- Kidney infection that can damage kidney tissue
- Permanent loss of kidney function (chronic kidney disease)
- High blood pressure that becomes harder to control
- Kidney failure requiring dialysis or a transplant
Long-term outlook
Most kidney problems found with a MAG3 scan can be treated or managed effectively, especially when caught early. With the right care, many people maintain good kidney function and quality of life for many years.
Find support
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
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Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 16, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.
Guidance may differ by country or region. Confirm local recommendations with a qualified healthcare provider.