The three physiologic strictures of the ureter are located at the beginning of the ureter, at the point where the iliac vessels are crossed, and at the point where the tube runs away from the wall of the bladder, which is the location where urinary stones tend to be retained. The ureters are a pair of elongated muscular tubes located in the posterior aspect of the peritoneum. The first physiologic stricture exists at the beginning of the ureter where the ureter joins the renal pelvis, the second at the point where the ureter crosses over the iliac vessels, and the third at the point where the ureter passes obliquely through the bladder wall. The three physiologic narrowings of the ureter are due to their alignment and do not lead to obstruction, but they are areas where urinary stones tend to remain. When a ureteral stone causes obstruction, you should seek medical attention and treatment under the direction of your doctor.