Vesicoureteral Reflux

Basics

Description

Vesicoureteral reflux (VUR) occurs when urine passes backward from the bladder to the ureters or kidneys.

Epidemiology

Prevalence

VUR occurs in ∼1% of children. There are 2 different groups of patients:

  • Those who were detected prenatally without any history of urinary tract infection (UTI)
    • ∼20–30% of patients with prenatal hydronephrosis have VUR. Screening this population for VUR is controversial.
    • The ratio of males to females in this group is 3:1. This ratio is believed to be caused by a period of high-pressure voiding in boys, which resolves by 18 months.
  • Those who were detected after an acute UTI
    • ∼30–50% of children with a febrile UTI will have VUR.

Risk Factors

Genetics

  • 30% of siblings will have VUR (usually low-grade), and the great majority will have been asymptomatic with only rare renal scarring.
  • Parents with VUR have a 60% chance of having children with VUR:
    • Whether or not to screen siblings is controversial as low-grade VUR usually resolves without treatment or sequelae.
    • One may elect to screen siblings with a history of recurrent febrile illnesses even in the absence of definitely diagnosed UTIs.

Pathophysiology

  • VUR in combination with UTI can lead to pyelonephritis, renal scarring, and possibly end-stage renal disease.
  • Primary VUR is classified into 5 grades by the International Reflux Study based on the voiding cystourethrogram (VCUG):
    • Grade I: reflux into ureter
    • Grade II: reflux into renal pelvis without dilation of calyces
    • Grade III: blunting of calyces, mild dilation of ureter
    • Grade IV: grossly dilated ureter, moderate calyceal dilation with maintained papillary impressions
    • Grade V: grossly dilated ureter with loss of papillary impressions
  • The grading scale is important because spontaneous resolution rates are very different between grades I–III and grades IV–V.

Etiology

  • A combination of abnormal anatomy and abnormal voiding pressure:
    • Primary VUR results from either a short ureteral tunnel through the bladder wall or transient high-pressure voiding, which occurs normally in the first 18 months of life.
    • Patients with primary low-grade VUR can expect improvement and even resolution of the VUR with time as the ureteral tunnel grows or when bladder pressures decrease.
  • Secondary VUR occurs when there is an associated lesion responsible for the abnormal anatomy or increased intravesical (bladder) pressure:
    • Patients with secondary reflux require treatment of their primary problem and still may require surgery to treat their secondary reflux.
    • Secondary reflux may occur in neurologically normal patients with bladder and bowel dysfunction, ureteroceles, posterior ureteral valves, and prune belly syndrome or in neurologically abnormal patients with spina bifida.
    • The distinction between primary and secondary reflux is important because large prospective trials have been conducted on patients with primary reflux and it is not appropriate to extend those findings to patients with secondary reflux.
    • Another important distinction is whether the diagnosis of VUR was made as a result of a prenatal diagnosis of hydronephrosis or whether the child presented with UTI.

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