Most common site of obstetric injury leading to uretero vaginal fistula:

The crossing of the uterine vessels and ureter is at the level of internal os. Over here the ureter runs below the uterine vessels (water below the bridge) and the distance between the ureter and uterine vessels is only 1.5–2 cm. The ureter can get injured at all the sites mentioned in the question but during gynaecological surgeries the commonest site of injury to ureter is where it crosses below the uterine arteries. The next common site of injury is behind the infundibulopelvic ligament at the pelvic brim. Close anatomical association between ureter and genital organs may lead to ureteric injury during gynecological surgery. Incidence: 0.5–1% of all pelvic operations. The sites of ureteric injuries are shown in Figure. • At or below the pelvic brim (I) • Along the course of ureter on lateral pelvic wall above the uterosacral ligaments (II) • In the base of broad ligament where the ureter passes beneath the uterine vessels, about 1.5 cm lateral to cervix at the level of internal orifice (III) • Beyond the uterine vessels as the ureter passes in the tunnel in Mackenrodt’s ligament and turns anteriorly and medially to enter the bladder (IV) • In the intramural portion of bladder (V).