Vesicoureteral reflux (VUR) is the retrograde urine flow from the urinary bladder to the upper urinary tract, usually during voiding. A short intramural ureter often causes this abnormal backward flow of urine. The clinical significance of VUR was not recognized until 1960, when the condition was associated with recurrent urinary tract infections (UTIs), renal cortical scarring, and permanent kidney damage, particularly in children. VUR is the most prevalent urological abnormality in neonates, occurring in approximately 1% of all newborns. However, this percentage rises significantly, up to 15%, in those diagnosed with prenatal hydronephrosis.

VUR is 3 times more prevalent in White than Black patients and twice as likely in women than men, except for cases identified with prenatal hydronephrosis, where VUR is more commonly found in boys. A systematic review of 34 studies indicated that approximately 16% of neonates with ultrasound evidence of hydronephrosis eventually have VUR. When tested, about 30% to 40% of children with a febrile UTI exhibit some degree of VUR, compared to 17% of patients without UTI evidence. In phenotypically male infants with dilated ureters, the odds for the presence of VUR are significantly higher, while in infants with UTI, the prevalence of VUR increases to over 66%.

A genetic predisposition for the disorder exists, as up to two-thirds of children born to women with primary VUR will also exhibit the condition. The incidence of primary VUR is very high in twins. Among siblings, the incidence of VUR is about 30%, although routine screening of asymptomatic siblings with normal renal ultrasound examinations is presently not recommended. VUR may also be associated with other congenital conditions such as posterior urethral valves, neurogenic bladder, spina bifida, urinary outlet obstruction, bladder overactivity, imperforate anus, ureterocele, and bladder exstrophy.

VUR can be asymptomatic, unilateral or bilateral, or associated with nephropathy, which can be severe. End-stage renal failure in children due to reflux nephropathy accounts for about 5% of all pediatric renal transplants. However, early diagnosis and timely treatment of VUR can prevent renal damage and recurrent UTIs and salvage the kidneys.

Bladder or bowel dysfunction includes lower urinary tract abnormalities in children, including detrusor overactivity, urinary urgency, urge incontinence, hypoactive bladder, postponement of urination, and other voiding disturbances. These conditions may be accompanied by gastrointestinal and bowel disorders such as encopresis and chronic constipation. Bladder or bowel dysfunction is more commonly found in females.