I think that I can quite confidently say that noone in the hospital will give a second thought to your tummy/knickers/bush/boobs/farting etc they do these ops all of the time and once you are in their hands you arent Kelly the woman, you are Kelly the patient, a body on bed that has medical needs and thats all.
Worry about many things guys but seriously dont worry about those little silly bits, the staff really dont even consider those things.
As for the keeping your undies on...if they need to catheterise you it doesnt matter if you go into surgery with them on, they will whip them off. I had one and the nurse had to keep checking it, so she quite often had to stare at my chuff and I honestly didnt care, that was the least of my worries.
So let go of those worries.
Steph xx