Vesicoureteral reflux: Types, causes, and symptoms

Vesicoureteral reflux is a condition in which urine flows in the wrong direction, from the bladder back into the ureter. It is most common in infants and young children, but it can affect older children and adults, too.

It can happen if the valve between the ureter and the bladder does not work properly, as the result of a congenital defect or a urinary tract infection (UTI).

Vesicoureteral reflux (VUR) can also cause an infection, because bacteria can develop in the urine. Without treatment, kidney damage may occur.

Studies suggest that between 25 and 40 percent of children who have a UTI also have VUR.

Fast facts on vesicoureteral reflux:

Here are some key points about the vesicoureteral reflux. More detail is in the main article.

Vesicoureteral reflux is when urine flows the wrong way, back towards the kidneys.

It usually affects infants and young children but it can happen at any age.

It is associated with urinary tract infections (UTI), but it is usually caused by a faulty valve that is present from birth.

It normally resolves itself, but treatment may be needed to prevent kidney damage.

Types and causes

In vesicoureteral reflux, a faulty valve causes urine to flow back toward the kidneys.
In vesicoureteral reflux, a faulty valve causes urine to flow back toward the kidneys.

Normally, urine is created in the kidneys and filters out through the ureters into the bladder and then out through the urethra. The urine flows in one direction only.

In vesicoureteral reflux (VUR), urine flows in the wrong direction, from the bladder back into the ureters. One in 10 children are thought to have VUR. In most cases, it is due to a faulty valve that was present at birth.

There are two types:

Primary VUR is when an infant is born with a faulty valve between one or both ureters and the bladder. If the ureter is too short, the valve does not close properly, allowing urine to back up, or reflux, from the bladder to the ureter. In severe cases, it can back up to one or both of the kidneys.

Primary VUR may resolve itself in time, as the ureter and valve function improve. Even if it is discovered at birth, no surgical intervention will normally be performed until the infant is at least several months old.

Secondary VUR happens when pressure causes urine to flow backward, usually because of a blockage somewhere in the urinary system. This may be a bladder infection that makes the ureters swell, causing urine to flow back to the kidneys.

Left untreated, VUR can lead to kidney damage and infection, because bacteria can grow in the trapped urine.

Infants and very young children are more likely to have VUR than older children or adults. It is most common in children aged 2 to 3 years. If a parent or sibling has had primary VUR, the chance of a child being born with it is higher.

According to the American Urological Association, VUR is often diagnosed after a UTI, as VUR can predispose a person to developing a UTI.

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Signs and symptoms

Symptoms of VUR are variable. In mild reflux, urine backs up just a short distance into the ureter. If reflux is severe, it can result in kidney infections and permanent kidney damage.

A urinary tract infection (UTI) is the most common indication of VUR, but it does not cause it. A UTI may develop without noticeable signs or symptoms, but it is also a common source of fever in infants, both boys and girls.

Without treatment, there is a risk of the infection from a UTI spreading to the kidneys and causing permanent scarring.

Signs and symptoms of a bladder infection or a UTI may be:

urgency to urinate

a burning sensation or pain when urinating

blood in the urine

cloudy urine

urine with a strong, unpleasant smell

dribbling urine, incontinence, and bed-wetting

fever and abdominal pain


These may be less noticeable in infants.

Signs of a kidney infection are:


pain in the abdomen or back

feeling unwell


Long-term symptoms, if VUR is not treated, include:

a palpable abdominal mass, caused by a swollen kidney

poor weight gain

hypertension, or high blood pressure

kidney failure

protein in the urine

scarring of kidney tissue

An infant may have vomiting, diarrhea, lethargy, and may not be growing normally.

When to see a doctor

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