The junction between the pelvis of the kidney and the ureters is known as the ureteropelvic junction or ureteral pelvic junction, and the junction between the ureter and the bladder is known as the ureterovesical (ureter-bladder) junction. At the entrance to the bladder, the ureters are surrounded by valves known as ureterovesical valves, which prevent vesicoureteral reflux (backflow of urine).