Vesicoureteral Reflux (VUR)

Overview

Vesicoureteral reflux (VUR) occurs when urine flows backward from the bladder through the ureters toward the kidneys, reversing the normal direction of urine flow. In a healthy urinary system, urine travels one way—from the kidneys through the ureters to the bladder, then out through the urethra. The ureters enter the bladder wall at an angle, creating a natural valve mechanism that closes when the bladder contracts. In VUR, this valve fails to function properly, allowing urine to reflux back toward the kidneys during voiding or when bladder pressure rises.

VUR affects approximately 1% of children in the general population, though the condition appears in 30-40% of children who present with a febrile urinary tract infection. The condition runs strongly in families—siblings of affected children have a 25-35% chance of also having VUR, and children of affected parents have a 50-60% chance. Girls are diagnosed more commonly in clinical practice, though boys are more often identified through prenatal ultrasound showing hydronephrosis.

The primary concern with VUR is that bacteria from bladder infections can travel backward to the kidneys, causing pyelonephritis (kidney infection). Repeated kidney infections can lead to reflux nephropathy—permanent kidney scarring that may result in high blood pressure, chronic kidney disease, or in severe cases, kidney failure.

Types of VUR

Primary VUR is the most common form and results from a congenital abnormality in how the ureter connects to the bladder. The tunnel through the bladder wall is too short or enters at too steep an angle, preventing proper valve function. Primary VUR often improves or resolves completely as children grow and the ureter-bladder junction matures. This type has a strong genetic component.

Secondary VUR develops because of another underlying condition that increases bladder pressure or obstructs urine outflow. Common causes include bladder neck obstruction, posterior urethral valves in boys, and neurogenic bladder. Unlike primary VUR, secondary VUR will not resolve until the underlying condition is treated.

VUR Grades

Doctors classify VUR into five grades based on voiding cystourethrogram (VCUG) findings, which guides treatment decisions and helps predict outcomes.

Grade I is the mildest form, with reflux reaching only into the ureter without affecting the kidney. This grade usually resolves spontaneously.

Grade II involves reflux that reaches the kidney’s collecting system (renal pelvis) without causing any dilation of the ureter or kidney. Most cases resolve with growth.

Grade III shows mild to moderate dilation of the ureter and kidney, with some blunting of the calyces (cup-shaped structures that collect urine in the kidney).

Grade IV demonstrates moderate dilation with more significant blunting of the calyces and some tortuosity (twisting) of the ureter.

Grade V represents the severest form, with gross dilation of the ureter, renal pelvis, and calyces, marked ureteral tortuosity, and loss of the normal papillary impressions in the kidney. This grade rarely resolves without intervention.

Symptoms

Many children with VUR have no symptoms until they develop a urinary tract infection. In infants, a febrile UTI is the most common presentation. Parents may notice unexplained fever, irritability, poor feeding, vomiting, failure to gain weight normally, or occasionally jaundice. Since infants cannot describe urinary symptoms, fever without an obvious source should prompt investigation.

Older children with VUR may experience recurrent urinary tract infections, fever accompanying UTIs, abdominal or flank pain, and urinary symptoms such as frequent urination, urgency, or pain with urination. Some children develop bedwetting or daytime wetting. The presence of recurrent febrile UTIs in any child warrants evaluation for VUR.

Some children are diagnosed before any symptoms occur. Prenatal ultrasound may detect hydronephrosis, prompting postnatal investigation that reveals VUR. Siblings of children with VUR may be screened and found to have the condition despite being completely asymptomatic.

Causes

Primary VUR develops during fetal development when the ureter-bladder junction forms abnormally. The ureter normally tunnels through the bladder wall at a shallow angle, creating a flap valve effect—as the bladder fills and the wall stretches, it compresses the ureter closed. When this tunnel is too short or too steep, the valve mechanism fails.

Secondary VUR occurs when elevated bladder pressures force urine backward through otherwise normal ureters. Conditions causing secondary VUR include bladder outlet obstruction from posterior urethral valves, neurogenic bladder from spinal cord abnormalities, and severe bladder dysfunction. Bladder diverticula can also contribute to reflux. Treating the underlying cause is essential in secondary VUR, as the reflux will persist until bladder dynamics normalize.

Diagnosis

After a child experiences a febrile UTI, current guidelines recommend starting with a renal ultrasound. This non-invasive test shows kidney size, structure, and any dilation of the collecting system. While ultrasound cannot directly diagnose VUR, abnormal findings or a history of recurrent UTIs typically prompt further investigation.

The voiding cystourethrogram (VCUG) remains the gold standard for diagnosing and grading VUR. During this test, a catheter is placed in the bladder and filled with contrast material. X-ray images are taken as the bladder fills and as the child voids. If reflux is present, the contrast will be seen traveling backward into the ureters and kidneys, allowing accurate grading.

A radionuclide cystogram uses a radioactive tracer instead of contrast dye and delivers less radiation than a VCUG, making it useful for follow-up studies. However, it provides less anatomical detail than a VCUG. A DMSA renal scan assesses kidney function and identifies scarring from previous infections, helping determine whether any permanent damage has occurred.

Treatment

Treatment goals focus on preventing kidney infections, avoiding new kidney scarring, and allowing normal kidney development while monitoring for spontaneous resolution.

Conservative management is appropriate for many children, particularly those with low-grade VUR. Watchful waiting involves regular monitoring with periodic ultrasounds and prompt treatment of any UTI that develops. Many cases of grade I-II VUR resolve within five to seven years without intervention.

Antibiotic prophylaxis involves giving a low daily dose of antibiotics to prevent UTIs while waiting for VUR to resolve. Commonly used medications include trimethoprim-sulfamethoxazole and nitrofurantoin. Recent studies have questioned the benefit of long-term prophylaxis, and its use remains somewhat controversial. This approach may continue for years until the reflux resolves or surgery is performed.

Bladder and bowel management is critical for all children with VUR. Parents should encourage regular, complete voiding, ensure adequate fluid intake, and treat constipation aggressively. Children with associated bladder dysfunction may need additional management of overactive bladder or voiding dysfunction.

Endoscopic injection (commonly using Deflux) offers a minimally invasive option. A substance is injected at the ureter opening during cystoscopy, creating a bulge that prevents reflux. This outpatient procedure has success rates of 70-90% depending on VUR grade and may need to be repeated.

Surgical reimplantation provides definitive correction by repositioning the ureter within the bladder wall to create a proper valve tunnel. Open surgery achieves success rates over 95% but requires hospitalization. Robotic and laparoscopic approaches offer faster recovery while achieving similar outcomes.

Surgery is typically recommended for high-grade VUR (grades IV-V), breakthrough UTIs despite prophylaxis, new kidney scarring, failure to resolve over time, inability to tolerate or comply with antibiotic prophylaxis, or based on family preference.

When to See a Doctor

Any child with fever and no obvious source should be evaluated for UTI. Seek prompt medical attention if your child develops fever with urinary symptoms, has recurrent urinary tract infections, experiences flank or abdominal pain with fever, or shows signs of poor growth.

Children with diagnosed VUR require regular follow-up with blood pressure monitoring, periodic ultrasounds, and assessment of kidney function if scarring is present. VCUG may be repeated periodically to assess for resolution.

Parents of children with VUR should learn to recognize UTI symptoms and seek evaluation promptly when they occur. Early treatment of infections reduces the risk of kidney scarring. Women with a history of VUR should inform their obstetrician during pregnancy, as they face increased UTI risk and need monitoring of kidney function.

Long-term blood pressure monitoring is essential for anyone with a history of VUR, particularly those with documented kidney scarring. Hypertension from reflux nephropathy may develop years after the VUR itself has resolved, making ongoing surveillance a lifelong consideration.