ABSTRACT
After entering the pelvis the ureters (1,2) lie anteromedial to branches of the internal iliac artery (3). In the female they lie posterior to the ovaries, before passing medially and anteriorly toward the bladder base, inferior to the uterine arteries, just lateral to the vaginal lateral fornices. In the male the vas deferens (4) crosses above and anterior to the ureter. The ureters enter the posterolateral corners of the trigone and pass obliquely through the bladder wall, creating a flap-valve effect, to prevent urinary reflux.
