Vesicoureteric reflux is a condition where urine flows backward from the bladder into the tubes that connect to the kidneys, affecting mostly babies and young children. While this backward flow might sound alarming, many children outgrow the condition naturally, and those who need treatment have several effective options available to protect their kidney health.

What Is Vesicoureteric Reflux?

Under normal circumstances, your body’s urinary system works like a one-way street. The kidneys produce urine, which travels down two thin muscular tubes called ureters to reach the bladder. The bladder stores this urine until you’re ready to empty it, and then the urine exits through a tube called the urethra. This system is designed so that once urine reaches the bladder, it should stay there and not flow backward.^[1]

Vesicoureteric reflux disrupts this normal flow pattern. In this condition, urine flows in the wrong direction—backward from the bladder into one or both ureters, and sometimes all the way up to the kidneys. This happens because the valve-like mechanism that normally prevents backflow doesn’t work properly. Think of it like a door that should only swing one way but instead allows movement in both directions.^[2]

The condition most commonly affects newborns, infants, and young children under the age of two, though older children and even adults can have it too. The main concern with vesicoureteric reflux is that when urine flows backward, it can carry bacteria from the bladder up to the kidneys, potentially causing infections that may lead to permanent kidney damage if left untreated.^[3]

Types and Grades of the Condition

Vesicoureteric reflux comes in two main types. Primary VUR is the most common form, where a child is born with a ureter that doesn’t connect properly into the bladder. The tunnel that the ureter normally creates as it passes through the bladder wall is too short, which means the flap valve between the ureter and bladder doesn’t close correctly. Primary VUR typically affects just one ureter and one kidney, though it can affect both.^[1]

Secondary VUR occurs when something blocks the urinary tract, causing pressure to build up and push urine backward. This blockage might be an abnormal fold of tissue in the urethra that prevents urine from flowing freely out of the bladder, or it could be a problem with the nerves that control bladder emptying. Children with secondary VUR often have reflux affecting both ureters and both kidneys.^[1]

Doctors classify vesicoureteric reflux into five grades based on how far the urine backs up and whether the ureter becomes enlarged. Grade one is the mildest, where urine backs up only into the ureter without causing it to widen. Grade two means urine reaches the area where the ureter meets the kidney, but without causing swelling. Grade three involves mild to moderate dilation of both the ureter and the kidney’s collecting system. Grade four shows more significant dilation. Grade five is the most severe, with substantial dilation and twisting of the ureter.^[5]

Epidemiology

Understanding how common vesicoureteric reflux is helps put the condition in perspective. About one in three children who develop a urinary tract infection accompanied by fever has VUR. However, the true number of children with the condition may be higher, because some children who have VUR but no symptoms or problems never get tested for it.^[3]

Age plays a significant role in who develops this condition. Generally, the younger a child is, the more likely they are to have vesicoureteric reflux. The condition is most common in infants and children ages two and under. During infancy, VUR is more frequently seen in boys, likely because the pressure in their urinary tract during urination is higher. However, as children grow older, the condition becomes more commonly diagnosed in girls.^[6]

Family history matters considerably with this condition. If one child in a family has VUR, there’s a good chance their siblings might have it too. More than one in four siblings of children with VUR will also have the condition. The connection is even stronger between parents and children—more than one in three children whose parent had VUR will develop it themselves. For this reason, doctors often recommend screening younger siblings of affected children, even if they show no symptoms.^[3]

Causes

The root cause of primary vesicoureteric reflux lies in how the urinary system develops before birth. Normally, as a baby grows in the womb, the ureters grow long enough to create a tunnel through the bladder wall. This tunnel acts like a valve—when the bladder fills with urine and its wall stretches, the tunnel collapses and prevents urine from flowing backward. In children born with primary VUR, the ureter didn’t grow long enough during prenatal development. It enters the bladder at an abnormal angle, which means the tunnel is too short to create an effective valve.^[12]

For secondary vesicoureteric reflux, the causes are different and often develop after birth. Any condition that creates a blockage in the urinary tract can cause secondary VUR. When urine can’t flow out of the bladder easily, pressure builds up inside. This increased pressure can force urine backward into the ureters and kidneys. Blockages might come from structural problems like abnormal folds of tissue in the urethra, or from functional problems where the bladder doesn’t empty properly.^[1]

Children with certain medical conditions face higher risks of developing vesicoureteric reflux. Those born with neural tube defects such as spina bifida (a condition where the spinal cord doesn’t develop properly) are more susceptible because nerve problems can affect how the bladder functions. Children with other urinary tract abnormalities—including conditions with complex names like posterior urethral valves, ureterocele, or bladder exstrophy—are also more likely to have VUR.^[6]

Risk Factors

Several factors increase the likelihood that a child will develop vesicoureteric reflux. Having a family history of the condition is one of the strongest risk factors. Because VUR often runs in families, children whose parents or siblings had the condition should be monitored more closely. This genetic component suggests that certain inherited traits affecting urinary tract development can be passed from one generation to the next.^[8]

Being born with abnormalities of the kidneys or urinary tract raises the risk substantially. Sometimes these abnormalities are detected even before birth during routine prenatal ultrasounds, which might show swollen kidneys in the developing baby. This swelling, called hydronephrosis, can be a sign that vesicoureteric reflux might be present after the baby is born.^[8]

Certain bathroom habits and behaviors can contribute to the development or worsening of VUR. Children who have severe abnormal urinating patterns—such as holding their urine for excessively long periods—may be at higher risk. Problems with bladder and bowel function can also be related to vesicoureteric reflux, creating a cycle where one problem makes the other worse.^[3]

Symptoms

Many children with vesicoureteric reflux show no obvious symptoms at all. The condition itself doesn’t typically cause pain or discomfort, which is why it often goes undetected until something else brings it to light. Most commonly, doctors discover VUR because a child develops a urinary tract infection, particularly one that causes fever.^[8]

When symptoms do appear, they’re usually related to urinary tract infections rather than the reflux itself. A urinary tract infection in the lower urinary system—affecting the bladder—can cause a child to feel an urgent or frequent need to urinate. The child might have accidents during the day or wet the bed at night, even if they were previously dry. Urination may cause a burning sensation, and the urine itself might contain blood, look cloudy, or smell unusual.^[8]

If the infection reaches the upper urinary system—the ureters or kidneys—symptoms become more serious. The child might experience pain in their side, back, or belly. Fever and chills often accompany these upper urinary tract infections, signaling that the kidneys are involved. This type of infection, called pyelonephritis, is particularly concerning because repeated kidney infections can lead to scarring and permanent kidney damage.^[3]

Prevention

Because vesicoureteric reflux is often a condition children are born with, there’s no guaranteed way to prevent primary VUR. The structural problem with the ureter develops during pregnancy, before parents even know their child might be affected. However, if VUR runs in your family, being aware of this increased risk allows you to watch for early signs and seek prompt medical attention if your child develops symptoms.^[17]

What can be prevented are the complications of vesicoureteric reflux, particularly kidney infections and the damage they can cause. The key is recognizing and treating urinary tract infections quickly. If your child shows signs of a UTI—such as painful urination, frequent trips to the bathroom, fever, or belly pain—see a doctor right away. Quick treatment with antibiotics can stop bacteria from reaching the kidneys.^[3]

For children diagnosed with VUR, doctors may recommend preventive antibiotics. These are low doses of antibiotics taken daily to prevent bacteria from multiplying in the urinary tract. The goal is to keep the urinary system free from infection until the child either outgrows the reflux or receives treatment to correct it. This approach works on the principle that sterile urine flowing backward won’t damage the kidneys—only infected urine poses a serious risk.^[13]

Maintaining good bathroom habits can also help reduce complications. Encourage your child to urinate regularly throughout the day rather than holding it for long periods. Making sure children empty their bladder completely each time they urinate helps prevent bacteria from multiplying. For older children, addressing any problems with bladder or bowel function may help improve the underlying reflux.^[3]

Pathophysiology

To understand how vesicoureteric reflux affects the body, it helps to know how the urinary system normally works at a mechanical level. When the ureters enter the bladder, they don’t just poke straight through. Instead, they travel through the bladder wall at an angle for a certain distance, creating a tunnel. As the bladder fills with urine and its wall stretches, this tunnel gets compressed, which closes off the opening and acts like a one-way valve. This clever design means that when the bladder contracts to empty, urine can only go out through the urethra, not back up the ureters.^[4]

In children with primary vesicoureteric reflux, this valve mechanism fails because the ureter’s tunnel through the bladder wall is too short. When the bladder fills and its wall stretches, there isn’t enough tunnel length to create proper compression. The opening where the ureter meets the bladder stays open instead of closing, which allows urine to flow backward. The severity of reflux depends partly on how abnormal this connection is—the shorter the tunnel and the more abnormal the angle, the worse the reflux tends to be.^[15]

Secondary VUR involves different physical changes. When a blockage prevents urine from flowing normally out of the bladder, pressure builds up inside the bladder during urination. This abnormally high pressure can be strong enough to force urine backward through the ureter openings, even if those openings were initially normal. Over time, this repeated high pressure can damage the valve mechanism, making the reflux worse. The bladder muscle itself may also change, becoming thicker and less elastic as it works harder to push urine past the blockage.^[1]

The kidneys suffer consequences when urine repeatedly flows backward into them. High pressure from refluxing urine can damage the delicate kidney tissues over time. More importantly, if bacteria are present in the bladder, they get carried up to the kidneys during reflux episodes. The kidneys aren’t designed to handle bacterial invasions, and repeated infections trigger inflammation and scarring. This scarring, called renal scarring, represents permanent damage where functional kidney tissue is replaced by non-functional scar tissue. As more scarring accumulates, the affected kidney loses its ability to filter blood effectively.^[4]

The body’s natural growth and development can actually help resolve vesicoureteric reflux over time. As children grow, their ureters grow longer too. This increased length can allow the ureter to create a longer tunnel through the bladder wall, which may be sufficient to establish proper valve function. This explains why many children, especially those with lower grades of reflux and those diagnosed at younger ages, naturally outgrow the condition without needing surgery. The younger the child and the milder the reflux, the better the chances of spontaneous resolution.^[13]