Vesicoureteral reflux (VUR) is a condition where urine flows backward from the bladder up toward the kidneys. Normally, urine travels a one-way path: from the kidneys, down through tubes called ureters, and into the bladder for storage. In VUR, a faulty valve at the point where the ureter connects to the bladder allows urine to reverse course. The condition is most common in infants and young children, and it ranges from mild to severe.
Why Urine Flows the Wrong Way
Where each ureter enters the bladder, there’s a valve-like mechanism that acts as a one-way gate. When the bladder fills or squeezes during urination, this valve is supposed to shut tight and prevent urine from being pushed back up. In children with VUR, that valve doesn’t close properly, so urine slips backward into the ureter and sometimes all the way up to the kidney.
There are two types. Primary VUR is the kind children are born with. The valve simply didn’t develop correctly, and it’s by far the more common form. Many children with primary VUR eventually outgrow it as the valve matures with age. Secondary VUR happens when something else prevents the bladder from emptying normally. That could be a physical blockage, abnormally narrow muscles at the bladder outlet, or nerve damage that affects how the bladder contracts. In secondary VUR, the underlying problem creates pressure that forces urine backward.
Symptoms to Watch For
VUR itself doesn’t always cause obvious symptoms. Many children show no signs at all until they develop a urinary tract infection, which is the most common way the condition is discovered. In babies and toddlers, a UTI can look like unexplained fever, irritability, poor feeding, or slow weight gain, none of which point clearly to a urinary problem.
Children with VUR are also more likely to have bladder and bowel issues that may seem unrelated. These include bedwetting, daytime wetting accidents, difficulty fully emptying the bladder, and constipation. If your child has repeated UTIs or a combination of these bladder and bowel symptoms, VUR is one of the conditions a doctor will consider.
How VUR Is Graded
VUR is rated on a scale from grade I to grade V, based on how far the urine travels backward and how much the urinary tract has stretched as a result. This grading system, developed by the International Reflux Study in Children, helps doctors decide how aggressively to treat.
- Grade I: Urine backs up into the ureter only, not reaching the kidney.
- Grade II: Urine reaches the kidney’s collecting area (the renal pelvis) but hasn’t caused any stretching.
- Grade III: The ureter and renal pelvis are mildly stretched, with minimal changes to the kidney’s drainage structures.
- Grade IV: Stretching is more pronounced, and the normal sharp angles inside the kidney’s drainage system are blunted.
- Grade V: The ureter, renal pelvis, and internal kidney structures are severely swollen. The kidney’s normal internal architecture is largely distorted.
Lower grades (I and II) are more likely to resolve on their own. Higher grades carry a greater risk of kidney damage and are more likely to need intervention.
How VUR Is Diagnosed
The standard test is a voiding cystourethrogram, commonly called a VCUG. During this test, a thin tube (catheter) is placed into the bladder through the urethra. A contrast dye that shows up brightly on X-rays is slowly pumped in to fill the bladder. X-ray images are taken as the bladder fills and again as the child urinates. If the dye travels backward into the ureters or kidneys, VUR is confirmed, and the grade is determined by how far the dye reaches and how much the structures have dilated.
The procedure takes about 30 to 60 minutes. It can be uncomfortable, especially for young children, though it’s not typically painful. Beyond VUR, the same test can reveal other structural problems like narrowed areas in the urethra or incomplete bladder emptying.
The Risk of Kidney Damage
The main concern with VUR isn’t the backward flow itself. It’s what that flow can carry with it. When urine reverses direction, bacteria from a bladder infection can be pushed up into the kidney, causing a kidney infection (pyelonephritis). Repeated kidney infections lead to scarring, a condition called reflux nephropathy. Over time, that scarring can permanently reduce the kidney’s ability to filter blood and regulate fluid balance.
Not every child with VUR develops kidney scarring. The risk depends on the grade of reflux, how often infections occur, and how quickly those infections are treated. Children with higher-grade reflux and recurrent febrile UTIs are most vulnerable. This is why preventing infections is central to managing the condition.
A Strong Genetic Component
VUR runs in families. Siblings of a child with VUR have a 30% to 50% chance of having it too, and the risk climbs higher if both parents have a history of the condition. Because of this, doctors often recommend screening younger siblings, even if they’ve never had a UTI. Catching it early allows for monitoring before infections or kidney damage occur.
Treatment Options
For mild to moderate VUR (grades I through III), the most common approach is watchful waiting. Since many children outgrow primary VUR as the valve mechanism matures, the goal is to prevent infections while the body has time to fix the problem. This typically means low-dose daily antibiotics to keep bacteria from gaining a foothold in the urinary tract, along with regular follow-up imaging to check whether the reflux is improving.
Managing bladder and bowel habits also plays a role. Encouraging regular bathroom trips, treating constipation, and making sure the child fully empties the bladder can reduce the pressure that drives reflux.
When Surgery Is Needed
If VUR doesn’t resolve on its own, causes repeated infections despite antibiotics, or is severe enough to threaten kidney health, surgery becomes an option. There are two main approaches.
Open surgical reimplantation repositions the ureter where it enters the bladder, creating a longer tunnel through the bladder wall so that the valve mechanism works properly. This approach has a 98% success rate in eliminating reflux and is considered the most reliable fix.
Endoscopic injection is a less invasive alternative. A bulking material is injected around the ureter opening to help the valve close more effectively. The procedure is quicker and recovery is easier, but it resolves reflux in about 70% of cases. Children who undergo the endoscopic approach are more likely to need repeat procedures and additional imaging compared to those who have open surgery.
The choice between the two depends on the child’s age, the grade of reflux, how well the child tolerates antibiotics, and how many infections have occurred. For high-grade reflux or cases where the endoscopic approach has already failed, reimplantation is generally the preferred route.