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Vesicoureteral Reflux (VUR) • Basics

What Is Vesicoureteral Reflux (VUR)?

Vesicoureteral reflux (VUR), sometimes called 'kidney reflux' in everyday language, is the backward flow of urine from the bladder toward the kidney through the ureter (the urine channel between the kidney and the bladder). It does not cause pain or symptoms on its own; what makes it important is that it can carry a urinary tract infection up to the kidney. This page explains the basic concepts for families who are hearing the diagnosis for the first time.

Who this is forFamilies who are hearing a diagnosis of VUR for the first time or who are just beginning to research the topic
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ByProf. Dr. Ali AvanoğluUpdated
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01 · What exactly does VUR mean?02 · How common is it?03 · Why does reflux matter?04 · How is it noticed, and how is it diagnosed?05 · Does it go away on its own, and how is it treated?
In brief5 madde
  • What exactly does VUR mean?: The kidneys produce urine, two thin channels called ureters carry it to the bladder, and once the bladder fills, the urine is passed out.
  • How common is it?: In the general child population, VUR is estimated to occur in around 1% of children; however, because it is silent, in most children it resolves with growth without…
  • Why does reflux matter?: Reflux itself does not cause the child pain, does not disrupt urination, and does not harm the kidney on its own.
  • How is it noticed, and how is it diagnosed?: VUR comes to light through three routes: a febrile urinary tract infection, kidney enlargement detected on a prenatal or postnatal ultrasound, or screening carried…
  • Does it go away on its own, and how is it treated?: As the child grows, the ureter's tunnel within the bladder wall lengthens and the valve mechanism strengthens; because of this, a significant proportion of VUR…
01

What exactly does VUR mean?

The kidneys produce urine, two thin channels called ureters carry it to the bladder, and once the bladder fills, the urine is passed out. In a healthy system this flow is one-way: the ureter travels through an oblique tunnel within the bladder wall, and as the bladder fills and contracts, this tunnel closes like a valve, preventing urine from flowing back upward.

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  • In vesicoureteral reflux, this valve does not close properly; while the bladder is filling or during urination, some of the urine flows back into the ureter, and in more advanced cases, all the way up into the kidney's collecting system. In medical terms, 'vesico' refers to the bladder, 'ureteral' to the ureter, and 'reflux' to the backward flow. It is often called 'kidney reflux' or simply 'VUR' for short; it has nothing to do with acid reflux.
  • One distinction needs to be made clear from the start: the 'urine leak' or 'backflow' referred to here is urine moving within the body from the bladder toward the kidney. A child wetting themselves or wetting the bed at night (enuresis) is a different matter; the two can sometimes occur together, but they are not the same thing.
02

How common is it?

In the general child population, VUR is estimated to occur in around 1% of children; however, because it is silent, in most children it resolves with growth without ever being noticed. Its frequency varies considerably depending on which group is being studied.

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  • When children with febrile urinary tract infections are investigated, VUR is found in about 25–40% of them; this is the most common route by which the diagnosis is made. In babies found to have antenatal hydronephrosis (kidney enlargement seen before birth), reflux is seen in about 10–20% on postnatal evaluation. Children with a sibling or parent with a history of reflux also have a higher frequency than the general population; this is why sibling and child screening comes up.
  • Among those diagnosed in infancy, boys predominate, especially cases noticed before birth and high-grade cases; after toilet-training age, girls diagnosed through febrile infection come to the fore. This distribution is not coincidental, and it is later reflected in treatment decisions.
03

Why does reflux matter?

Reflux itself does not cause the child pain, does not disrupt urination, and does not harm the kidney on its own. The problem is that bacteria multiplying in the bladder can be carried up to the kidney by the refluxing urine; in that case, a febrile kidney infection (pyelonephritis) can develop.

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  • Recurrent or late-treated kidney infections can leave permanent scarring in the kidney tissue, known as reflux nephropathy. If the scarring is extensive and on both sides, the risk of high blood pressure and reduced kidney function increases over the years. In a subset of high-grade cases, particularly in boy infants, some kidney damage is not related to infection at all; it is a congenital developmental deficiency (dysplasia) that is already present at the time of diagnosis.
  • So the real goal in VUR is not to 'erase' the reflux itself, but to protect the child from febrile infection and the kidney from scarring. Most decisions are made with this perspective in mind; for some children careful monitoring alone is enough, while others need medication or a procedure.
04

How is it noticed, and how is it diagnosed?

VUR comes to light through three routes: a febrile urinary tract infection, kidney enlargement detected on a prenatal or postnatal ultrasound, or screening carried out because of a family history of reflux. In infants, unexplained fever is often the only clue.

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  • A kidney–bladder ultrasound is done first for diagnosis; however, ultrasound does not directly show reflux, and a normal result does not rule it out. A definitive diagnosis and grading are made with a voiding cystourethrogram (VCUG); at some centers, contrast-enhanced voiding urosonography (ceVUS), a radiation-free option, is used instead. Whether there is scarring in the kidney is assessed with a DMSA renal scan.
  • Not every child with a febrile infection immediately undergoes a voiding cystourethrogram; age, how often the infection recurs, ultrasound findings, and family history are all weighed together.
05

Does it go away on its own, and how is it treated?

As the child grows, the ureter's tunnel within the bladder wall lengthens and the valve mechanism strengthens; because of this, a significant proportion of VUR resolves on its own over the years. The chance of resolution varies with grade: about 70–80% for low grades, and around 10–15% for the highest grade, as reported in the literature.

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  • Treatment steps proceed in the order of active surveillance, antibiotic prophylaxis (CAP), endoscopic injection (placing a bulking agent beneath the ureteral opening; Deflux), and, when needed, ureteral reimplantation (reattaching the ureter to the bladder). In children who have completed toilet training, constipation and voiding habits (bladder-bowel dysfunction, BBD) are reviewed before every decision.
  • In our practice, diagnosis, monitoring, endoscopic injection, and reimplantation are carried out jointly by two pediatric urology specialists; follow-up continues with the same team through the transition to adolescence and adulthood. The most important thing for families to understand at this stage is that VUR is not an emergency, but it does require planned follow-up in which fever must be taken seriously.
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Frequently asked questions
Is kidney reflux the same thing as acid reflux?
No. In acid reflux, stomach contents flow back up into the esophagus; in kidney reflux (VUR), urine flows backward from the bladder toward the kidney. Only the word 'reflux,' meaning 'backward flow,' is shared between them; their causes, diagnosis, and treatment are completely different.
Does reflux cause my child pain or discomfort?
No, it does not. Reflux itself cannot be felt; the child only shows symptoms — fever, fussiness, or flank pain — when an infection develops. That is why, after diagnosis, fever is the main thing to watch for.
Does VUR always require surgery?
No. Most children are followed with monitoring or antibiotic prophylaxis, and the reflux resolves on its own with growth. Injection or surgery comes into consideration for children who develop a febrile infection despite prophylaxis, develop new kidney scarring, or have high-grade reflux that does not resolve.
Does a diagnosis of reflux mean kidney failure?
No. In the vast majority of children with reflux, kidney function is normal and stays that way. What threatens kidney function is extensive scarring on both sides or a congenital developmental deficiency; this occurs in only a small number of children and is caught early through regular follow-up.
Next • BasicsVUR Symptoms: Signs in Babies and Children→
Related pagesFull index →
BasicsVUR Symptoms: Signs in Babies and ChildrenVesicoureteral reflux (VUR) does not cause a symptom of its own; in most children, the first and only clue is a febrile urinary tract infection. In babies, this infection shows up as fever with no obvious cause; in older children, it shows up as flank pain, chills, and voiding complaints. This page explains which signs should raise suspicion.BasicsWhat Causes VUR? Primary and Secondary RefluxVesicoureteral reflux (VUR) results from the tunnel through which the ureter passes within the bladder wall failing to act properly as a valve. In most children, this tunnel is short from birth (primary VUR); in a smaller group, high pressure inside the bladder overwhelms the valve instead (secondary VUR). This distinction determines where treatment starts.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.Diagnosis and evaluationVCUG (Voiding Cystourethrogram): How It's Done, and PreparationThe VCUG (voiding cystourethrogram) is the main method that both shows and grades vesicoureteral reflux (VUR). A thin catheter is used to fill the bladder with contrast fluid; as the bladder fills and the child voids, it is imaged to see whether urine backs up into the kidney. This page explains how the procedure is done, how to prepare, radiation, and the alternatives.
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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