Together these features produce a valvelike effect that occludes the ureteric opening during storage and voiding of urine. In people with VUR, failure of this mechanism occurs, with resultant backward (retrograde) flow of urine. Primary VUR
Insufficient submucosal length of the ureter relative to its diameter causes inadequacy of the valvular mechanism. This is precipitated by a congenital defect or lack of longitudinal muscle of the portion of the ureter within the bladder resulting in an ureterovesicular junction (UVJ) abnormality. Secondary VUR
In this category the ureters valvular mechanism is initially intact and healthy but becomes overwhelmed by increased bladder pressures associated with obstruction, which distorts the ureterovesicular junction. The obstructions may be anatomical or functional. Secondary VUR can be further divided into anatomical and functional groups. Anatomical
Posterior urethral valves; urethral or meatal stenosis. These causes are treated surgically when possible. Functional
Bladder instability, neurogenic bladder and non-neurogenic bladder. Bladder infections may cause reflux due to the elevated pressures associated with inflammation.Resolution of functional VUR will usually occur if the precipitating cause is treated and resolved. Medical and/or surgical treatment may be indicated.
Surgical management
A surgical approach is necessary in cases where a breakthrough infection results despite prophylaxis, or there is non-compliance with the prophylaxis. Similarly if the VUR is severe (Grade IV & V), there are pyelonephritic changes or congenital abnormalities. Other reasons necessitating surgical intervention are failure of renal growth, formation of new scars, renal deterioration and VUR in girls approaching puberty. There are four types of surgical procedure available for the treatment of VUR: endoscopic (STING/HIT procedures); laparoscopic; robotic-assisted laparoscopic; and open procedures (Cohen procedure, Leadbetter-Politano procedure, Lich-Gregoir technique). Laparoscopic and robotic-assisted laparoscopic procedures are often imitation of classical open procedures  in laparoscopic or robotic-assisted laparoscopic environments. Surveillance
The American Urological Association recommends ongoing monitoring of children with VUR until the abnormality resolves or is no longer clinically significant. The recommendations are for annual evaluation of blood pressure, height, weight, analysis of the urine, and kidney ultrasound. Epidemiology
It has been estimated that VUR is present in more than 10% of the population. Younger children are more prone to VUR because of the relative shortness of the submucosal ureters. This susceptibility decreases with age as the length of the ureters increases as the children grow. In children under the age of 1 year with a urinary tract infection, 70% will have VUR. This number decreases to 15% by the age of 12. Although VUR is more common in males antenatally, in later life there is a definite female preponderance with 85% of cases being female.