What is a Dynamic Renal Scintigraphy?
Dynamic renal scintigraphy, also called a renogram or a renal scan, is a specialized imaging test that evaluates how well your kidneys are functioning. This test provides important information about:
- Overall kidney function
- Blood flow to your kidneys
- How efficiently your kidneys filter waste products
- Whether there are any blockages in your urinary system
- How well urine flows from your kidneys to your bladder
The test uses a small amount of radioactive tracer (Tc-99m MAG3) that is filtered by your kidneys, allowing doctors to see how your kidneys are working in real time.
Why Might I Need This Test?
Your doctor may recommend this test to:
- Evaluate kidney function, especially if you have known or suspected kidney disease
- Detect blockages (obstructions) in your urinary tract
- Investigate the cause of high blood pressure that might be related to kidney issues
- Assess kidney function before or after surgery
- Monitor a kidney transplant
- Determine when dialysis might be necessary for patients with kidney failure
- Identify abnormal backflow of urine from the bladder to the kidneys (vesicoureteral reflux)
- Evaluate kidney function in children with urinary tract abnormalities
Types of Renal Tracers
Different radioactive tracers may be used depending on what specific aspect of kidney function your doctor needs to evaluate, we use:
- MAG3: Evaluates tubular function (how well your kidney cells process and secrete waste)
Preparing for Your Test
- Continue taking your regular medications unless instructed otherwise
- Stay well-hydrated before your appointment (unless your doctor advises otherwise)
- Wear comfortable clothing
- Inform your healthcare team if you:
- Are pregnant or breastfeeding
- Have recently had other nuclear medicine tests or X-ray studies with contrast
- Have any allergies
What to Expect During the Procedure
Before the Scan
- You’ll be asked to drink 2-3 glasses of water (approximately 500-750ml) prior to the test
- This ensures you are well-hydrated, which is important for accurate results
- Children will be given an appropriate amount of fluid based on their size
- You’ll be asked to empty your bladder just before the scan begins
- An IV line will be placed in a vein in your arm
During the Scan
- You’ll lie on an examination table with the gamma camera positioned over your kidneys and bladder
- The radioactive tracer will be injected through your IV
- You won’t feel any effects from this tracer
- The camera will begin taking images immediately after injection
- First, quick images assess blood flow to your kidneys
- Then, images track how the tracer moves through your kidneys
- You’ll need to lie still during the imaging, which typically lasts about 20-30 minutes
- If your kidneys aren’t emptying normally after 20 minutes, you may receive a diuretic medication (like furosemide/Lasix) through your IV
- This medication makes your kidneys produce more urine
- Additional images will be taken for another 20-30 minutes to see how your kidneys respond
- If your bladder fills during the test, you may be asked to empty it
- Before and after images may be taken to evaluate the effect of bladder emptying on kidney drainage
- For certain conditions, special imaging protocols may be used:
- For suspected urine reflux: Images may be taken while you’re urinating to check if urine flows backward
- For suspected renovascular hypertension (high blood pressure due to kidney artery narrowing): Two separate scans may be performed, with and without medication
Special Considerations for Children
- The procedure is similar but adapted for children’s comfort
- Parents or guardians may stay in the room
- Child-friendly distraction techniques may be used
- For young children who cannot cooperate with lying still, mild sedation might occasionally be considered
After Your Test
- You can resume normal activities immediately
- Drink plenty of fluids for the rest of the day to help flush the tracer from your body
- The small amount of radiation used will naturally leave your body within 24 hours
- A nuclear medicine specialist will analyze your images and send a report to your doctor
- Your doctor will discuss the results with you at your follow-up appointment
What Do the Results Mean?
The test provides several important measurements:
- How quickly the tracer appears in each kidney (blood flow)
- How efficiently each kidney processes the tracer (function)
- How well the tracer drains from the kidneys to the bladder (drainage)
These measurements help your doctor determine if your kidneys are functioning normally or if there are problems with blood flow, filtering ability, or drainage.
Are There Any Risks?
The dynamic renal scan uses a very small amount of radiation. The benefits of the information gained far outweigh any potential risks from this minimal radiation exposure. The diuretic medication occasionally used during the test may cause a temporary increase in urination.
How Long Will the Entire Procedure Take?
- Standard procedure: 1-1.5 hours
- If additional imaging is needed (such as with diuretic): 2-3 hours
- For specialized protocols (like renovascular hypertension assessment): May require two separate visits
If you have any questions or concerns about your dynamic renal scintigraphy, please discuss them with your healthcare provider.
