Commonest cause of ureteric injury during surgical operation is

Surgical trauma during pelvic surgery is the most common cause of ureteric trauma This occurs most often during vaginal or abdominal hysterectomy when the ureter is mistakenly divided, ligated, crushed or excised. Pre-emptive ureteric catheterisation makes it easier to identify the ureters. ( ref : Bailey 27th ed , chap 76 , pg no 1415 )