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Prof. Dr. Ali Avanoğlu
Vesicoureteral Reflux (VUR) • Diagnosis and evaluation

DMSA Renal Scan: Scarring and Function

The DMSA renal scan is the test that shows whether vesicoureteral reflux (VUR) has damaged the kidney: it reveals both the areas affected by kidney infection (pyelonephritis) and permanent marks (scarring), as well as each kidney's contribution to overall function (split function). This page explains when and why a DMSA is done, how it's performed, and how to read the result.

Who this is forFamilies whose child has been referred for a DMSA scan, or who are trying to understand the result
Reading≈6 min
ByProf. Dr. Ali AvanoğluUpdated
This page is part of vesicoureteral reflux.Read the full treatment overview on the hub page
RIGHT%55RELATIVE FUNCTIONLEFT%45RELATIVE FUNCTIONDashed ring: scarring; function shifts to the other kidney
DMSA: a single scar
01 · What is DMSA, and what does it show?02 · In the acute phase, or 4–6 months later?03 · What does split function mean?04 · How is it done, preparation, and radiation05 · What does the result mean, and what happens next?
In brief5 madde
  • What is DMSA, and what does it show?: DMSA (dimercaptosuccinic acid) is a substance bound to a very low dose of radioactive tracer (technetium-99m); it is given intravenously and taken up by functioning…
  • In the acute phase, or 4–6 months later?: The timing of a DMSA depends on the question being asked.
  • What does split function mean?: Normally, the two kidneys share the workload nearly equally; split function means each contributes roughly 45–55%.
  • How is it done, preparation, and radiation: The procedure has two parts: first the tracer is given intravenously, then there is a 2–4 hour wait, followed by imaging that takes about 20–30 minutes.
  • What does the result mean, and what happens next?: If there is no scarring and function is balanced, this is the most reliable evidence that reflux has not damaged the kidney, and it supports a follow-up plan.
01

What is DMSA, and what does it show?

DMSA (dimercaptosuccinic acid) is a substance bound to a very low dose of radioactive tracer (technetium-99m); it is given intravenously and taken up by functioning kidney tissue. Imaging with a gamma camera a few hours later maps out the functioning tissue of both kidneys.

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  • Areas affected by infection or bearing permanent damage show up on this map as reduced uptake, usually as a wedge-shaped defect or a thinned cortex. Small scars that ultrasound can miss are clearly visible on DMSA; this is why it is the reference method for diagnosing reflux nephropathy (kidney scarring).
  • From the same scan, each kidney's contribution to overall function (split function) is calculated as a percentage; a kidney that has failed to grow, is abnormally positioned, or is congenitally underdeveloped is also identified this way.
02

In the acute phase, or 4–6 months later?

The timing of a DMSA depends on the question being asked. If done in the first days of a febrile infection, it shows whether the infection has reached the kidney (pyelonephritis); in the ‘top-down’ approach, this information is used to decide whether a VCUG is needed. However, most acute-phase involvement heals and leaves no trace.

  • About 4–6 months after a febrile UTI: is there permanent scarring?
  • During the acute phase of infection: is the kidney involved (in the top-down approach)?
  • High-grade (III–V) reflux or an abnormal ultrasound: baseline evaluation
  • A new febrile infection during follow-up, a new ultrasound finding, or before a treatment decision: is there new or progressing scarring?
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  • To see permanent scarring, it needs to be done at least 4–6 months after the infection; findings seen before this time has passed can be transient and could saddle the child with an unnecessary ‘scar’ label. Guidelines recommend a DMSA 4–6 months later in a child who has had a febrile UTI, especially one with high-grade reflux or an abnormal ultrasound.
  • In an infant found to have reflux through antenatal hydronephrosis, before ever having had an infection, DMSA is used to document the kidneys' baseline status; any abnormality seen here may be due not to infection but to a congenital developmental defect (dysplasia). This distinction matters for follow-up and treatment decisions.
03

What does split function mean?

Normally, the two kidneys share the workload nearly equally; split function means each contributes roughly 45–55%. A kidney's share dropping below 40% is considered a meaningful asymmetry; values below 10–15% show that kidney is barely functioning. Thresholds can vary somewhat by center.

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  • This ratio is not the same as total kidney function. While one kidney's share is low, the other can grow and take over the work, and blood tests (creatinine, estimated filtration rate) can remain completely normal. Total function is monitored separately with blood and urine tests, blood pressure, and growth.
  • Split function is most meaningful when tracked over time: a decline on follow-up DMSA scans, together with a new or growing scar, is among the findings that push treatment to the next step.
04

How is it done, preparation, and radiation

The procedure has two parts: first the tracer is given intravenously, then there is a 2–4 hour wait, followed by imaging that takes about 20–30 minutes. During the wait, the child may leave the hospital and eat or drink; fasting is not necessary, and there is no restriction related to contrast allergy or kidney function. Drinking plenty of fluids and voiding before imaging are recommended.

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  • The child needs to stay still during imaging. Infants can usually be scanned while breastfeeding or asleep; some centers use light sedation for restless young children. Starting the IV line is the only part of the procedure that hurts; numbing cream helps.
  • The radiation dose is low and given at amounts adjusted for the child; no known harm has been shown at this level. Even so, DMSA is requested only when the result will affect the decision, and unnecessary repeats are avoided; routine, frequent DMSA is not needed in every child with reflux.
05

What does the result mean, and what happens next?

If there is no scarring and function is balanced, this is the most reliable evidence that reflux has not damaged the kidney, and it supports a follow-up plan. If scarring is present, two questions are asked: is it congenital (usually a male infant, high grade, prenatal diagnosis), or is it due to a past kidney infection? Acquired scarring shows just how important it is to prevent recurrent infection.

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  • Scarring alone is not a reason for surgery; but when a new or progressing scar, loss of function, and a febrile infection occurring despite antibiotic prophylaxis come together, endoscopic injection or ureteral reimplantation come up for discussion. In a child with scarring, long-term monitoring of blood pressure and protein in the urine also becomes especially important.
  • In our practice, the DMSA result is evaluated together with the ultrasound, the VCUG, and the child's history by two specialists; both the treatment decision and long-term follow-up continue with the same team.
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Frequently asked questions
The DMSA showed scarring — is my child's kidney heading toward failure?
Usually not. A one-sided, limited scar generally does not affect overall function if the other kidney is healthy. The risk rises with bilateral, widespread scarring and with progressive loss of function. In a child with scarring, the main precautions are annual blood pressure and urine monitoring, along with preventing new infections.
Couldn't it be done right after the febrile infection?
A DMSA done in the acute phase shows that the infection has involved the kidney, but it does not show permanent scarring; most involvement at that stage heals. For a permanent mark, 4–6 months are allowed to pass. Acute-phase DMSA is used only at centers that follow the top-down approach and for a specific purpose.
How often is DMSA repeated?
Routine, frequent repeats are not needed. It is repeated 4–6 months after a new febrile infection, when a new finding appears on ultrasound, or to document baseline status before a treatment decision. With no scarring and no infections, it may not need to be repeated for years.
Will my baby be put to sleep — is there a needle?
A single needle stick is needed to start the IV line; numbing cream can be used. Because the child needs to stay still during imaging, infants are usually scanned while breastfeeding or asleep; some centers use light sedation for restless young children. General anesthesia is not needed.
←Previous • Diagnosis and evaluationVCUG (Voiding Cystourethrogram): How It's Done, and PreparationNext • Diagnosis and evaluationUrinalysis and Urine Culture in Children: How to Collect the Right Sample→
Related pagesFull index →
Kidney health and infectionIs Kidney Reflux Dangerous? Reflux Nephropathy and Renal ScarringThe honest answer to “is kidney reflux dangerous?” has two sides: reflux itself is harmless and temporary in most children; what truly matters is whether permanent kidney damage — reflux nephropathy, renal scarring — develops alongside a febrile infection. This page explains what scarring is, its two different types, how it is detected with DMSA, which children are at higher risk, and what can be prevented.Kidney health and infectionDoes VUR Cause Kidney Failure? Blood Pressure, Proteinuria, and FunctionThe deepest worry for families of children with kidney reflux (vesicoureteral reflux, VUR) is kidney failure. The truth is this: reflux itself does not cause kidney failure; the long-term risk is limited to the small number of children with extensive scarring in both kidneys, and even in these children, blood pressure and kidney function can be preserved for years with regular follow-up. This page explains how hypertension, proteinuria, and kidney function are monitored.Kidney health and infectionPyelonephritis in Children (Febrile UTI): Symptoms and When It's an EmergencyPyelonephritis is a febrile urinary tract infection (febrile UTI) in which bacteria travel up from the bladder and reach the kidney tissue. In children, it is the most common way kidney reflux first comes to light, and it is the main cause of scarring — which is why rapid diagnosis and timely treatment matter so much. This page covers symptoms by age, the warning signs for urgent care, how treatment is planned, and what is investigated afterward.Diagnosis and evaluationVUR Evaluation After a Febrile Urinary Tract Infection: Who Needs a VCUG?Roughly 25–40% of children who have a febrile urinary tract infection (UTI) are found to have vesicoureteral reflux (VUR). But that doesn't mean every child needs an immediate VCUG. This page explains which test is done for whom, in what order, and when, after an infection.
Vesicoureteral Reflux (VUR) topic clustersMain treatment page →
Basics 6Diagnosis and evaluation 6By age and special situations 5Bladder and bowel 5Treatment pathways 10Kidney health and infection 5After treatment and follow-up 6
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