What anatomical structures do the ureters commonly cross anterior to, which can cause constriction or obstruction?

The ureters commonly cross anterior to the common iliac arteries, which is significant as this anatomical relationship is a known site where the ureters may experience constriction or obstruction. The common iliac arteries branch from the abdominal aorta and run laterally to become the internal and external iliac arteries, at which point the ureters descend into the pelvis. This anatomical position is particularly important in both surgical and clinical contexts because any pathologies, such as nearby tumors or vascular anomalies, can lead to ureteral obstruction at this site.

In contrast, while the ureters do have relationships with the abdominal aorta and the renal arteries, these structures do not typically represent the anatomical sites of significant constriction or obstruction for the ureters. The inferior mesenteric arteries also do not have a direct relationship with the ureters that would lead to constriction or obstruction, as they are located higher in the abdominal cavity and further from the ureters' course. Understanding the anatomical relationships of the ureters can help in diagnosing and managing conditions like hydronephrosis or urinary obstruction.