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Prof. Dr. Ali Avanoğlu
Vesicoureteral Reflux (VUR) • Kidney health and infection

Is Kidney Reflux Dangerous? Reflux Nephropathy and Renal Scarring

The 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.

Who this is forFamilies of children diagnosed with kidney reflux, and families told a scar was found on DMSA
Reading≈7 min
ByProf. Dr. Ali AvanoğluUpdated
This page is part of vesicoureteral reflux.Read the full treatment overview on the hub page
RIGHT%62RELATIVE FUNCTIONLEFT%38RELATIVE FUNCTIONDashed rings: multiple scarred areas
DMSA: multiple scars
01 · Is kidney reflux dangerous? A balanced answer02 · What are reflux nephropathy and renal scarring?03 · Two types of scarring: congenital dysplasia and acquired infection-related scarring04 · How is scarring detected: DMSA renal scan05 · Which children are at higher risk of scarring?06 · Can scarring be prevented?
In brief5 madde
  • Is kidney reflux dangerous? A balanced answer: Kidney reflux (vesicoureteral reflux, VUR) does not cause pain on its own, does not make a child sick, and resolves on its own over the years in the large majority of…
  • What are reflux nephropathy and renal scarring?: A renal scar is an irreversible area in the kidney's outer layer (cortex) where functioning tissue has been replaced by connective tissue.
  • Two types of scarring: congenital dysplasia and acquired infection-related scarring: One of the most common pieces of misinformation given to families is the statement that “every scar is the result of a past infection.” In fact, reflux nephropathy…
  • How is scarring detected: DMSA renal scan: The standard way to demonstrate renal scarring is the DMSA renal scan.
  • Which children are at higher risk of scarring?: The risk of scarring is not the same for every child.
01

Is kidney reflux dangerous? A balanced answer

Kidney reflux (vesicoureteral reflux, VUR) does not cause pain on its own, does not make a child sick, and resolves on its own over the years in the large majority of cases. So it isn't accurate to say “reflux is dangerous” — but calling it “unimportant” would be incomplete, too.

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  • Reflux matters for two reasons. First, urine that flows backward from the bladder to the kidney can carry bacteria from the bladder up into the kidney, opening the way to pyelonephritis (kidney infection). Second, repeated pyelonephritis episodes can leave some children with a permanent mark on the kidney tissue — a scar. This is what we call reflux nephropathy.
  • The reassuring fact is this: most children with reflux grow up without ever developing a scar, and among those who do develop one, the scar is usually limited and kidney function is preserved. Our job is to identify early the small group of children at high risk and to prevent infection in them.
02

What are reflux nephropathy and renal scarring?

A renal scar is an irreversible area in the kidney's outer layer (cortex) where functioning tissue has been replaced by connective tissue. On a scan it appears as a wedge-shaped area of reduced uptake or as cortical thinning.

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  • If the scar is small and one-sided, it usually causes no symptoms at all; the opposite kidney and the healthy remaining part of the same kidney take over the workload. The problem arises when the scarring is extensive or affects both kidneys — in that case, the risk of high blood pressure, protein leaking into the urine, and declining kidney function increases in later years.
  • Once a scar has formed it cannot be reversed; however, new scarring can be prevented, and the effects of an existing scar can be managed with regular follow-up.
03

Two types of scarring: congenital dysplasia and acquired infection-related scarring

One of the most common pieces of misinformation given to families is the statement that “every scar is the result of a past infection.” In fact, reflux nephropathy involves two different mechanisms, and distinguishing between them affects both feelings of guilt and treatment decisions.

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  • Congenital dysplasia: the kidney formed abnormally together with the reflux while developing in the womb. This pattern is seen more often in male infants, in high-grade (IV–V) reflux, and in cases first noticed through antenatal hydronephrosis (kidney enlargement seen before birth). Reduced uptake or a small kidney can be found on DMSA even before the baby has ever had an infection. This is not the result of any neglect — no one could have prevented it.
  • Acquired pyelonephritis scarring: the kidney was born healthy; a febrile infection (or infections) later on caused inflammation in the kidney tissue and, subsequently, a scar. This type of scarring is seen more often in girls, in children with a history of recurrent febrile UTIs, and after episodes where treatment was delayed. This is the type of scarring that can be prevented — and preventing it is exactly the goal of our efforts toward early diagnosis and treatment.
  • In real life the two mechanisms can overlap: a kidney that is congenitally weak can be damaged further by infections it goes on to have — which is why preventing infection is especially important in infants with high-grade reflux.
04

How is scarring detected: DMSA renal scan

The standard way to demonstrate renal scarring is the DMSA renal scan. A low-dose tracer given intravenously is taken up by functioning kidney tissue; areas where there is no uptake indicate scarring. The same study also measures each kidney's relative contribution to overall function (split function; the normal range is roughly 45–55%).

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  • Timing matters. A reduced-uptake area on a DMSA scan taken right after a febrile infection can reflect temporary inflammation that may still resolve; to confirm permanent scarring, the scan is repeated about 4–6 months after the infection. Ultrasound can pick up marked scarring and a small kidney, but it usually misses small scars — a normal ultrasound does not mean there is no scarring.
  • DMSA is not needed for every child with reflux. It is requested for children who have had a febrile UTI, who have high-grade or bilateral reflux, whose ultrasound is abnormal, or in situations where the treatment decision would depend on the presence of scarring.
05

Which children are at higher risk of scarring?

The risk of scarring is not the same for every child. The risk factors highlighted in the literature and in clinical guidelines are:

  • High-grade (III–V) reflux, especially when bilateral
  • Recurrent febrile urinary tract infections — each episode raises the risk a little further
  • A delayed start to treatment for febrile infection (fever lasting longer than roughly 48–72 hours before treatment begins)
  • Young age, especially pyelonephritis occurring within the first year of life
  • Bladder-bowel dysfunction (BBD): constipation and voiding dysfunction increase the recurrence of infection
  • Hydronephrosis detected before birth and an underlying congenital dysplasia
  • A scar previously detected on DMSA (also a marker of risk for new scarring)
06

Can scarring be prevented?

Congenital dysplasia cannot be prevented, but acquired scarring can largely be prevented. The three keys here are early diagnosis, prompt treatment, and reducing the recurrence of infection.

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  • Early diagnosis: in a child with known or suspected reflux, any fever of unclear origin should first be worked up with a urinalysis and urine culture. Labeling an unexplained fever as “probably viral” and waiting is the most common reason for delay. Starting effective antibiotic treatment within the first 48 hours of fever onset has been reported to reduce the risk of scarring.
  • Reducing infection recurrence: correcting constipation and voiding habits (BBD treatment), antibiotic prophylaxis in the right child, circumcision as an option for male infants, and, when needed, correcting the reflux with endoscopic injection or ureteral reimplantation all serve this goal. Studies (RIVUR, PREDICT) have shown that antibiotic prophylaxis reduces febrile infections, without showing a clear difference in new-scar rates over the short term; even so, preventing infection remains the main route to preventing scarring.
  • In our practice, the same two pediatric urology specialists carry this follow-up through from diagnosis to treatment; in a child with scarring, monitoring of blood pressure, urine, and kidney function continues without interruption into adolescence and adulthood.
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Frequently asked questions
My child has a scar — is this my fault?
No. A significant proportion of scars are present from congenital dysplasia, with no infection ever having occurred, and could not have been prevented. Even with an infection-related scar, it is often genuinely difficult to recognize the source of a fever in time. What can be done going forward is clear, though: a urine culture with every fever, regular follow-up, and preventive treatment if needed.
Does a scar heal over time?
A permanent scar does not reverse; however, some of the reduced uptake seen on a DMSA scan taken right after an infection reflects temporary inflammation, which can resolve within 4–6 months. For this reason, findings on an early DMSA scan are not interpreted as a definite scar — they are confirmed with a follow-up study.
Should I worry if there is a small scar in one kidney?
In the large majority of children with a limited, one-sided scar, kidney function and blood pressure remain normal for life. Even so, annual blood pressure checks, urinalysis, and ultrasound follow-up are recommended; the real risk lies with extensive, bilateral scarring.
If there is scarring, does the reflux have to be corrected surgically?
No. Scarring alone is not a reason for surgery; the decision is based on the grade of reflux, recurrence of infection, age, and whether BBD is present. In a child with scarring, having a febrile infection while on antibiotic prophylaxis, or developing a new scar, are situations that favor corrective treatment.
Can DMSA harm my child?
DMSA is a low-dose nuclear medicine study. Placing the IV line is the most difficult part for the child; no anesthesia is needed, and in most centers the child waits together with the family.
Prof. Dr. Ali Avanoğlu's publications on this topic · 1
  1. Ozel SK, Dokumcu Z, Akyildiz C, et al. (2007). Factors affecting renal scar development in children with spina bifida. Urologia internationalis. PubMed ↗
Next • Kidney health and infectionDoes VUR Cause Kidney Failure? Blood Pressure, Proteinuria, and Function→
Related pagesFull index →
Diagnosis and evaluationDMSA Renal Scan: Scarring and FunctionThe 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.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.BasicsWhat Do VUR Grades (1–5) Mean?Vesicoureteral reflux (VUR) is classified into five grades, from 1 to 5; the grade describes how far up the urine flows and to what extent the ureter and the kidney's collecting system are dilated. The grade is determined with a VCUG (voiding cystourethrogram) and is the strongest predictor of spontaneous resolution; however, it does not determine the treatment decision on its own.
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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