Vesicoureteral Reflux (VUR)

How reflux happens

Each ureter enters the bladder at an angle, tunneling through the bladder wall. When the bladder fills and contracts, this tunnel is squeezed shut, acting as a one-way valve. In primary VUR, the tunnel is too short, so the valve does not close properly. In secondary VUR, high pressure in the bladder forces urine backward, for example from posterior urethral valves in boys, a neurogenic bladder, or bladder dysfunction.

Grades of reflux

VUR is graded from I to V based on the voiding cystourethrogram:

Grades I and II often resolve on their own within a few years. Grades IV and V are less likely to resolve and carry more risk of kidney damage.

Who gets it

• Infants and young children, more often girls after infancy
• Siblings and children of people with VUR: about 1 in 3 siblings are affected
• Children with bladder and bowel dysfunction (constipation, holding urine)
• Babies with hydronephrosis on prenatal ultrasound

Symptoms

VUR itself does not cause symptoms. Problems arise from infections:

• Urinary tract infection with fever: in babies, fever may be the only sign, along with irritability, poor feeding or vomiting
• Kidney infection (pyelonephritis): fever, back or side pain, vomiting, feeling unwell
• Older children: burning on urination, urgency, frequency, wetting accidents, foul-smelling urine
• Constipation and daytime wetting, which often accompany VUR and worsen it

Diagnosis

1. Urinalysis and urine culture to diagnose UTI, collected by catheter or clean-catch method in young children.
2. Kidney and bladder ultrasound: checks for swelling (hydronephrosis), kidney size and scarring.
3. Voiding cystourethrogram (VCUG): contrast is placed in the bladder through a catheter and X-rays taken while the child urinates. It confirms and grades reflux.
4. DMSA scan: a nuclear scan that detects kidney scarring.

The AAP recommends ultrasound after a first febrile UTI in children aged 2 to 24 months, and a VCUG if the ultrasound is abnormal or after a second febrile UTI.

Treatment

Treatment is individualized, based on age, grade, kidney scarring, infection history and bladder and bowel function.

Observation

Many children with low-grade reflux and no recurrent infections are monitored, with prompt testing and treatment of any febrile illness.

Continuous antibiotic prophylaxis

A low daily dose of an antibiotic reduces recurrent UTIs, particularly in children with higher-grade reflux or bladder and bowel dysfunction. The decision balances fewer infections against antibiotic side effects and resistance.

Treating bladder and bowel dysfunction

• Treat constipation with diet, fluids and laxatives if needed
• Timed voiding every 2 to 3 hours
• Avoid holding urine
• Good hygiene and fluid intake

This is a key part of care and helps reflux resolve.

Procedures

• Endoscopic injection: a bulking gel is injected at the ureter opening through a cystoscope to create a valve. Outpatient, success rates around 70 to 90% depending on grade
• Ureteral reimplantation: open, laparoscopic or robotic surgery to lengthen the tunnel. Success rates above 95%

Procedures are considered for breakthrough infections despite antibiotics, new kidney scarring, high-grade reflux that persists, or family preference.

Secondary VUR

Treatment targets the underlying cause, such as ablation of posterior urethral valves or management of neurogenic bladder.

Complications

• Recurrent kidney infections
• Kidney scarring
• High blood pressure later in life
• Reduced kidney function and, rarely, chronic kidney disease
• Pregnancy complications in women with kidney scarring

Outlook

Most children with VUR, especially low grades, do well. Reflux often resolves by age 5 to 7. Prompt treatment of febrile UTIs is the most important step to protect the kidneys. Children with kidney scarring need long-term monitoring of blood pressure and kidney function.

Frequently asked questions

What is vesicoureteral reflux?

Vesicoureteral reflux is a condition in which urine flows backward from the bladder into the ureters and sometimes the kidneys. It is common in young children and increases the risk of kidney infections.

What causes VUR in children?

Most VUR is primary, caused by a short tunnel where the ureter enters the bladder, which lets urine flow back. It often runs in families. Secondary VUR results from high bladder pressure due to blockages or bladder dysfunction.

Does vesicoureteral reflux go away?

Often, yes. Many children with low-grade reflux (grades I and II) outgrow it within a few years as the bladder and ureter grow. Higher grades are less likely to resolve on their own.

How is VUR treated?

Options include watchful waiting, daily low-dose antibiotics to prevent UTIs, treating constipation and voiding problems, endoscopic injection of a bulking agent, or surgery to reimplant the ureter. The choice depends on grade, infections and kidney scarring.

What are the symptoms of reflux in babies?

VUR itself has no symptoms. Babies are usually diagnosed after a UTI, which may cause only fever, irritability, poor feeding or vomiting. Some cases are found on prenatal ultrasound showing a swollen kidney.