The ureters narrow at three sites on their course to the urinary bladder. These areas are known as constrictions and are clinically significant regions. They represent the most common sites for renal stones (renal calculi) to get stuck. It usually causes obstructed urinary flow.

Each ureter presents with the following three constrictions:

The first constriction is found at the ureteropelvic junction, where the renal pelvis narrows and transitions into the ureter. The ureteropelvic junction is positioned at the level of the L2 vertebra.
The second constriction is found at the site, where the ureters cross the iliac vessels and pelvic inlet. This site is not a true anatomical constriction. However, here, the ureters form sharp angles to enter the lesser pelvis, so larger and longer stones may have some difficulty passing through this area.
The third constriction matches the ureterovesical junction at which the ureters enter the wall of the bladder. This is the most common site where renal stones get stuck, as it is the narrowest portion of the ureter.

Unlock with Premium

Constrictions of ureters