Vesicoureteral Reflux

Vesicoureteral reflux (VUR) is the backward flow of urine from the bladder into the upper urinary tract. It is an abnormality that is associated with recurrent urinary tract infections and a particular form of renal damage known as reflux nephropathy. Because of its pathogenic role in reflux nephropathy, early recognition and eradication are essential. Primary reflux is the result of a congenital anomaly of the ureterovesical junction, whereas secondary reflux is the result of bladder outlet obstruction and high intravesical pressures.

PATHOPHYSIOLOGY

The most distal 13 mm of the ureter in adults lies intravesically (5 mm in neonates), including an intramural segment within the muscular wall of the bladder and a submucosal segment lying just beneath the bladder mucosa. This intravesical segment acts as a passive flap valve mechanism to prevent reflux. The ratio between the length of the submucosal segment and the diameter of the ureter (normal 4:1 or 5:1) is believed to be an important factor for normal function of the antireflux mechanism. Active peristalsis of the ureter also acts to prevent reflux.

Factors associated with VUR include the following:

A short submucosal tunnel
Lateral placement of the ureteral orifice
Abnormal configuration of ureteral orifice (e.g., stadium, horseshoe, and golf hole orifices)
Infection
Severe bladder outlet obstruction
Young age
Duplicated collecting systems (particularly from the more laterally placed orifice draining the lower pole)