Normal versus refluxing ureterovesical junctions

Illustration of the bladder wall depicting 2 different lengths for the intravesicular ureteral tunnel. Normally, in individuals with a normal-length intravesicular tunnel (panel A), reflux is prevented because the intravesical ureter is compressed as the bladder fills, acting as a flap valve. Individuals with short intravesicular ureteral tunnels are more likely to have vesicoureteral reflux (panel B). Mild vesicoureteral reflux in children may improve as the bladder grows and the tunnel lengthens, which improves the function of the antireflux mechanism.