The three strictures of ureter in human body are, from top to bottom, the stricture at the junction of renal pelvis and ureter (i.e. the beginning of ureter), the stricture at the junction of ureter and iliac vessels (i.e. the entrance of small renal pelvis) and the stricture inside ureter and bladder wall (i.e. the junction of ureter and bladder wall). These three physiological strictures are the areas where urinary calculi are easy to incarcerate and cause ureteral calculi.
At present, the upper 1/3 ureter is supplied by renal artery branches, the middle 1/3 ureter is supplied by abdominal aorta, common iliac artery, internal spermatic artery or uterine artery, and the lower 1/3 ureter is supplied by inferior bladder artery. After reaching the ureter, these branches are distributed in the fascia layer and communicate with each other from top to bottom, forming an arterial network and then spreading to other layers. Therefore, when doing ureteral transplantation, cutting off the lower 1/3 blood flow has little effect on the blood supply of the transplantation site. Ureteral vein returns with artery. Veins return to fascia through submucosa, and then return from kidney, ilium, spermatic cord, uterus, bladder vein, etc.