In males, the ureter passes under the ductus deferens, superior to the seminal vesicles.

In females, the ureter descends posterior to the ovary and into the base of broad ligament passing under the uterine artery (thus “water under the bridge”). At its’ origin the right ureter is usually covered by the descending part of the duodenum, and in its course downward lies to the right of the inferior vena cava, and is crossed by the  right colic and ileo colic vessels, while near the superior aperture of the pelvis it passes behind the lower part of the mesentery (the fold of membrane that attaches the small intestine to the back of the abdominal wall and carries its’ blood supply) and part of the ileum (the lowest (third) part of the small intestine).

The left ureter is crossed by the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its’ mesentery. At its’ termination the ureter passes through the urinary bladder wall in such a way as to close itself off from urine backflow as the urinary bladder fills with urine.