Introduction
A DMSA renal kidney scan is one of modern medicine’s best tools for checking kidney health. This test shows how well your kidneys work and can find problems other tests might miss. If you have kidney symptoms, a child with urinary infections, or possible kidney damage, this test can help.
This guide explains what happens during a DMSA scan, how it works, when doctors recommend it, and what the results mean. We want to help you better understand this important test.
What Is a DMSA Renal Kidney Scan?
A DMSA scan is a special test that checks both kidney function and structure. Dr. Sarah Johnson, Director of Nuclear Medicine at Northeastern Medical Center, explains it simply: “Unlike other scans that just show kidney shape, a DMSA scan shows how well kidney tissue is actually working.”
The test uses a tiny amount of radioactive material called technetium-99m DMSA. This material is given through an IV in your arm. It sticks to healthy kidney tissue and helps doctors see:
- The size, shape, and position of each kidney
- How well each kidney works compared to the other
- Any areas of scarring, infection, or damage
“DMSA scans can find subtle kidney problems that ultrasound or CT scans might miss, especially in children,” says Dr. Johnson.
How It Works
The Science Behind the Scan
A DMSA scan uses nuclear medicine to check kidney function. Here’s how it works:
- You get an IV injection of technetium-99m DMSA.
- The DMSA attaches to working kidney cells. Dr. Michael Rivera, a kidney specialist, explains: “DMSA sticks to the working cells in your kidneys. Areas with damage will show less DMSA.”
- The material gives off gamma rays that a special camera can detect.
- A computer turns these signals into detailed images of your kidneys.
“This amazing technology lets us see how cells in your kidneys are working, not just what they look like,” adds Dr. Rivera.
What to Expect During the Procedure
Here’s what happens during a DMSA scan:
- Preparation: You don’t need to stop eating or drinking before the test.
- Injection: You’ll get a small IV injection. This feels like a quick pinch, similar to a blood draw.
- Waiting Period: You’ll wait 2-3 hours while the material concentrates in your kidneys.
- Imaging: You’ll lie on a table while a camera takes pictures from different angles. This takes 30-60 minutes. Young children may need mild sedation to stay still.
- After the Test: You can resume normal activities right away. The radioactive material leaves your body within 24 hours.
Maria Sanchez, a clinical technologist, notes, “We make the test as comfortable as possible, especially for children. The scan itself doesn’t hurt, though staying still can be hard for kids.”
When Is a DMSA Scan Needed?
Doctors recommend DMSA scans in several situations when they need detailed information about kidney function.
For Children:
- Urinary Tract Infections (UTIs): “DMSA scans are the best way to check for kidney damage after UTIs in children,” says Dr. Elizabeth Wong, a pediatric urologist. “They show if the infection has reached the kidneys and if scarring has occurred.”
- Backward Urine Flow: Children with vesicoureteral reflux (when urine flows backward from the bladder to kidneys) may need this test.
- Birth Defects: The scan can check function in children born with kidney abnormalities.
For Adults:
- Kidney Injury: After trauma to the kidney area.
- High Blood Pressure: To check if kidney problems are causing high blood pressure.
- Kidney Function: To measure overall kidney health or compare function between kidneys.
- Kidney Infection: To confirm kidney infection and see how severe it is.
- Before Surgery: To check kidney function before certain procedures.
Dr. Wong adds, “Each case is different. We weigh the benefits of the test against the small radiation exposure, especially for children.”
Benefits of DMSA Scans
DMSA scans offer several advantages over other imaging tests:
- Shows Function: Unlike ultrasound or CT scans that show structure, DMSA scans reveal how well kidney tissue is working.
- Highly Sensitive: “DMSA scans can detect small scars other tests might miss,” says Dr. Johnson. Research shows DMSA scans find kidney scarring with 92% accuracy compared to 69% for ultrasound.
- Precise Measurement: The scan can show exactly how much each kidney contributes to overall function.
- Minimally Invasive: The procedure only needs an IV injection.
- Works for All Ages: The scan can be safely done on patients from infancy through adulthood.
Limitations to Consider
Despite its benefits, the DMSA scan has some drawbacks:
Radiation Exposure
The procedure uses a small amount of radiation. “We keep the radiation dose as low as possible, but it’s still something to consider, especially for children,” explains Dr. James Cortez, a medical physicist. “The radiation from a typical DMSA scan equals about 6-12 months of natural background radiation.”
Modern guidelines recommend careful use of DMSA scans in children. Doctors now use them more selectively rather than after every UTI.
Time Required
The procedure takes significant time:
- Injection of the material
- 2-3 hour waiting period
- 30-60 minutes for the actual scan
Reading the Results
Dr. Rivera notes, “While DMSA scans provide valuable information, reading them takes expertise. Sometimes acute infection and chronic scarring can look similar on scans.”
Cost and Availability
Not all hospitals have nuclear medicine facilities, especially in rural areas. The special equipment and materials make DMSA scans more expensive than some alternatives like ultrasound.
Understanding DMSA Scan Results
DMSA scan results provide key information about kidney health. Here’s what doctors look for:
Normal Results
In a normal DMSA scan:
- Both kidneys absorb the material evenly
- The kidney outlines appear smooth and clear
- Each kidney contributes about 45-55% to total kidney function
- No spots of decreased uptake are visible
Abnormal Findings
Several patterns may signal problems:
- Active Kidney Infection: “During kidney infection, we typically see patchy, uneven areas where less material is absorbed,” explains Dr. Wong. “These show temporarily damaged kidney tissue.”
- Kidney Scarring: Permanent kidney damage appears as well-defined areas with little or no material uptake. “Scarring means permanent damage to kidney tissue,” notes Dr. Rivera. “The extent and location of scarring help us determine outlook and guide treatment.”
- Uneven Function: Significant difference between kidneys (one kidney doing less than 40% of the work) may show disease affecting one kidney more than the other.
- Size and Shape Issues: The scan may reveal unusually small kidneys (suggesting chronic kidney disease) or abnormal positions.
Research shows that multiple or extensive DMSA defects are linked to higher risk of worsening kidney damage and high blood pressure.
Comparison with Other Kidney Tests
Several methods can check kidney health, each with distinct advantages:
Ultrasound
Renal ultrasound uses sound waves to create images of the kidneys.
Advantages compared to DMSA:
- No radiation exposure
- Widely available and less expensive
- Provides real-time imaging
- Can detect swelling or stones
Limitations: “Ultrasound mainly shows structure rather than function,” explains radiologist Dr. Amelia Park. “It can’t reliably detect active kidney infection or accurately assess scarring, especially small scars.”
CT Scan
Computed tomography uses X-rays to create detailed cross-sectional images.
Advantages compared to DMSA:
- Faster procedure
- Provides detailed structural information
- Can detect stones, tumors, and other abnormalities
Limitations:
- Higher radiation dose than DMSA scan
- Less sensitive for detecting focal kidney scarring
- Provides limited function information without contrast
MRI
Magnetic resonance imaging uses magnetic fields and radio waves to create detailed images.
Advantages compared to DMSA:
- No radiation exposure
- Excellent soft tissue detail
- Can provide some function information with certain methods
Limitations:
- More expensive and less widely available
- Often requires sedation for children
- Not safe for patients with certain implants
“Each imaging test has its place,” concludes Dr. Park. “The DMSA scan remains the gold standard for checking kidney scarring and function, but we often use multiple tests together to get a complete picture.”
Special Considerations for Children
Children make up many DMSA scan patients, mainly due to frequent urinary tract infections and reflux issues in this age group.
Current Guidelines
Pediatric kidney specialists have updated their recommendations for DMSA use. Dr. Wong explains, “Current guidelines suggest a more targeted approach rather than routine use after all UTIs. We now focus on children with unusual or repeated infections, those under 3 years old, and cases with concerning features.”
Expert guidelines recommend DMSA scans 4-6 months after UTI for:
- Children under 3 with unusual or repeated UTIs
- Children with abnormal ultrasound results
- Children with severe clinical infection
Making It Kid-Friendly
Special steps help make the procedure comfortable for children:
- Preparation: Child life specialists use age-appropriate explanations and play therapy to reduce anxiety.
- Sedation Options: “For younger children who can’t stay still, sedation may be necessary,” notes Dr. Thomas Grant, a pediatric anesthesiologist. “We use the minimum sedation needed, typically oral medications that keep breathing safe.”
- Parent Involvement: Many centers encourage parents to stay during the procedure to comfort their child.
- Radiation Protection: Pediatric departments use weight-based dosing to minimize radiation while maintaining image quality.
Future Trends and Research
Kidney imaging continues to advance, with several promising developments:
Lower Radiation Techniques
Researchers are developing methods that maintain accuracy while further reducing radiation. “New camera technologies and image processing allow us to get good images with lower doses,” says Dr. Cortez. “This is especially important for children.”
New Tracers
Research is exploring alternative materials that may offer advantages over traditional DMSA. Recent studies show new tracers may provide similar diagnostic information more quickly, potentially shortening the procedure.
Combined Approaches
“The future likely involves combining functional information from nuclear medicine with detailed anatomical data from other imaging methods,” predicts Dr. Park. Hybrid systems that combine SPECT with CT or MRI provide comprehensive structural and functional information in one exam.
Artificial Intelligence
Machine learning algorithms are being developed to help read DMSA scans. These tools show promise in:
- Automating kidney measurement
- Calculating relative kidney function more precisely
- Finding subtle abnormalities human eyes might miss
- Predicting outcomes based on imaging patterns
Living with Kidney Scarring
For patients diagnosed with kidney scarring on DMSA scans, understanding what it means is important for long-term health.
Outlook and Monitoring
The outlook for patients with kidney scarring varies depending on several factors:
- Extent of Scarring: “Limited scarring on one side typically has minimal impact on overall kidney function,” explains Dr. Rivera. “However, extensive scarring on both sides may increase risk of high blood pressure and worsening kidney function.”
- Age at Detection: Scarring found at younger ages may have more significant long-term effects.
- Other Conditions: The presence of factors like reflux or repeated infections affects outlook.
Long-term monitoring may include:
- Regular blood pressure checks
- Periodic blood tests to assess kidney function
- Checking for protein in urine
- Sometimes, follow-up imaging to check for progression
Prevention Strategies
For patients with kidney scarring, preventive measures are crucial:
- Quick UTI Treatment: “Recognizing and treating urinary infections promptly helps prevent additional kidney damage,” stresses Dr. Wong.
- Managing Contributing Factors: Addressing conditions like reflux through medicine or surgery when appropriate.
- Lifestyle Tips: Drinking plenty of fluids, practicing good hygiene, and following a kidney-friendly diet when needed.
Patient Experience
Sarah Thompson, whose daughter Emma was diagnosed with kidney scarring after repeated UTIs, shares: “Learning about Emma’s kidney scarring was scary at first, but understanding the condition helped us manage it effectively. We watch closely for UTI symptoms and see her kidney specialist regularly. The DMSA scan was crucial in helping us understand exactly what we were dealing with.”
Frequently Asked Questions
Is a DMSA renal scan painful?
The scan itself is painless. The only discomfort comes from the IV insertion, similar to having blood drawn. This discomfort lasts just a moment.
How long does a DMSA renal scan take?
The entire procedure takes about 3-4 hours. This includes the injection, a 2-3 hour waiting period, and 30-60 minutes for imaging.
Does a DMSA scan require special preparation?
Unlike many medical tests, DMSA scans need minimal preparation. You can eat and drink normally before the scan. Do tell your doctor about any medications you’re taking and any recent nuclear medicine tests.
Is the radiation from a DMSA scan dangerous?
The radiation exposure is relatively low and considered safe. Dr. Cortez explains, “The radiation dose is carefully calculated to be as low as possible while still providing good images. The long-term risk is extremely small, even in children.” Doctors always weigh benefits against risks when ordering the test.
Can pregnant women have DMSA scans?
DMSA scans are generally avoided during pregnancy unless absolutely necessary. The radioactive material could potentially affect the developing baby. Always tell your doctor if you are or might be pregnant.
What happens if my scan shows abnormalities?
If the scan reveals problems, your doctor will discuss the findings and their meaning with you. They may recommend:
- Additional imaging tests
- Treatment for conditions like infection
- Regular monitoring of kidney function
- Referral to specialists like urologists or kidney doctors
Can infants have DMSA scans?
Yes, DMSA scans can be safely performed on infants. Special considerations include weight-based dosing to minimize radiation and possibly mild sedation to keep the baby still during imaging.
Will I be radioactive after a DMSA scan?
The small amount of radioactive material is quickly eliminated from your body, mainly through urine. Drink plenty of fluids after the procedure to help flush the tracer out. As a precaution, minimize close, prolonged contact with pregnant women and young children for 24 hours after the scan.
How often can DMSA scans be repeated?
There’s no absolute limit, but doctors aim to minimize radiation by spacing scans appropriately. For conditions requiring follow-up, scans are typically scheduled no more often than every 6-12 months.
Are there alternatives to DMSA scans?
Yes, depending on what information is needed, alternatives might include ultrasound, CT scans, MRI, or other nuclear medicine studies like MAG3 scans. Your doctor will recommend the most appropriate test for your situation.
Conclusion
DMSA renal scans provide unique insights into kidney function and structure that other imaging tests can’t offer. They excel at finding subtle abnormalities, measuring relative kidney function, and identifying scarring. This makes them especially valuable for managing conditions like urinary tract infections, reflux, and congenital kidney problems.
While concerns about radiation have led to more careful use of these scans, particularly in children, they remain the best test for assessing kidney scarring. Ongoing advances promise even safer and more informative kidney imaging in the future.
For patients and families facing kidney health concerns, understanding DMSA renal scans can help navigate the diagnostic process with greater confidence. The information these scans provide often proves crucial for guiding treatment decisions and long-term health management strategies.