Specifically, the cervix is often significantly longer on the scan, compared with the digital examination (which presumably represents the fact that TVS measures the whole cervical length, including the supravaginal
portion), and TVS captures the cervix in a passive state, whereas during a digital exam, touching the cervix will stretch it to a variable dilatation.
With the more common blunt dissection during vaginal hysterectomy, the surgeon pushes the supravaginal septum and vesicocervical space upward with a finger on a piece of gauze or with a sponge stick in an attempt to expose or enter the anterior peritoneum.
With tissue forceps, he grasps the tissue that is exposed between the cut edge of the vagina and the cervix--the supravaginal septum--and incises it with scissors, keeping the handles of the scissors below the horizontal axis.
After the supravaginal septum is cut, the vesicocervical space is easily entered and more space is created by spreading the scissors laterally.