Vesicoureteral reflux is defined as the abnormal retrograde flow of urine from the bladder into the upper urinary tract through an incompetent ureterovesical junction. Low pressure reflux without bacterial contamination has not been documented to be harmful; however, reflux in the presence of infection is a risk factor for upper urinary tract infections (pyelonephritis). Untreated upper urinary tract infections have been shown to lead to acquired renal scarring (reflux nephropathy) in children. Congenital abnormalities of renal development may have associated vesicoureteral reflux resulting in a clinical picture of reflux nephropathy but without a history of urinary tract infection.

A. Reflux Nephropathy

It is defined as the following clinical triad.

1. Renal scarring

2. Hypertension

3. Vesicoureteral reflux

The prevalence of reflux varies with several demographic factors of the patient population. Reflux may occur as an isolated entity or with other associated anomalies of the genitourinary tract.

A. History of Urinary Tract Infection

In children without urologic symptoms or history of infection, the incidence of reflux is likely less than 1%. In children with a history of symptomatic urinary tract infection, the incidence of reflux has been estimated to range from 20% to 50%.

B. Age

The prevalence of reflux correlates inversely with the age of the study population. With linear growth, spontaneous resolution of reflux occurs in many patients.

C. Race

Reflux is more commonly a disease of fair-skinned children. The prevalence of reflux appears to be significantly lower in black children and children of Mediterranean origin when compared to white children. The prevalence of reflux in black children with a history of urinary tract infection is estimated to be approximately 25% of the incidence in the white children population.

D. Sibling Predisposition

Siblings of patients with known reflux have approximately a 30% prevalence of reflux, with younger siblings being at greatest risk. A voiding cystourethrogram (VCUG) is recommended if the sibling of a child
with VUR has abnormalities on screening renal and bladder ultrasound (RBUS) or has had a UTI.

E. Sex

Due to the epidemiology of urinary tract infection in children, boys and girls may present with reflux at different ages. Since urinary tract infections are more common in uncircumcised boys than girls during the neonatal period, many boys will be diagnosed with reflux in the neonatal period. However, after the first year of life, the incidence of urinary infections is much higher in girls than boys. Therefore most school-aged children diagnosed with reflux are girls.

F. Associated Anomalies

Although vesicoureteral reflux may occur as an isolated entity, reflux may also occur with other genitourinary abnormalities.

1. Posterior urethral valves: Congenital bladder outlet obstruction has been associated with reflux in up to 50% of patients. This would be considered secondary reflux.

2. Duplicated collecting system: Reflux is commonly associated with the lower pole moiety of a duplicated system.

3. Prune belly (Eagle-Barrett) syndrome.

4. Bladder exstrophy.

5. Severe voiding dysfunction.

6. Neurogenic bladder.

7. Ureterocele.

A. Primary Reflux

Primary reflux occurs as a result of a congenital deficiency in the formation of the ureterovesical junction in the absence of any other predisposing pathology. Accordingly, these patients may have a laterally ectopic ureteral orifice consistent with a deficient submucosal ureteral tunnel. The majority of otherwise healthy children who present with symptomatic urinary tract infection will fall into the category of primary reflux. It should be noted that the majority of the current guidelines, which have been developed to treat children with reflux, apply mainly to those patients with primary reflux.

B. Secondary Reflux

Secondary reflux occurs as a result of other urinary tract anomalies that secondarily cause a decompensation of a normally formed ureterovesical junction. Although secondary reflux may have many different underlying etiologies, the successful treatment of these patients ultimately depends upon the management of the underlying causes.

1. Neurogenic bladder

a. Myelomeningocele

b. Spinal cord injury or lesion

c. Anorectal abnormalities (imperforate anus)

2. Obstruction

a. Voiding dysfunction

b. Posterior urethral valves

c. Ectopic ureteroceles

3. Infection: Cystitis may also predispose an otherwise marginally competent ureterovesical junction (UVJ) to demonstrate reflux.

4. Bladder and bowel dysfunction: The combination of functional constipation and lower urinary tract symptoms is called bladder and bowel dysfunction (BBD). The pathophysiology of BBD is unclear. Rectal distention that comes with constipation may have a mass effect on the
bladder, which in turn leads to urinary dysfunction. Others believe that the rectal and urinary sphincters originate from a common neural network, which is dysfunctional. BBD may also predispose an otherwise marginally competent UVJ to demonstrate reflux (see Chapter 6).

Grading of the degree of reflux is important to the management and ultimate prognosis of the patients with primary reflux. More severe grades of reflux are associated with lower rates of spontaneous resolution and a higher incidence of renal scarring. According to the international system, grading of reflux is dependent upon the severity of calyceal changes, ureteral dilation, and redundancy that occur secondary to reflux (see Table 7-1, Fig. 7-1).

A. Urinary Tract Infection

Most children with reflux initially present with an episode of urinary tract infection. Pyelonephritis is the initial presentation in most cases.