I actually used to work in the medical field and although I never crossed any boundaries when I did, I've always had a thing for playing doctor. This is a long post so here goes...
So as far as play goes, I usually have a female patient who has a presenting symptom, usually something related to sexual dysfunction such as an inability to reach orgasm, a pronounced inhibition, or something along those lines. I instruct them to dress in something, well, slutty when they come to my "office". A conservative dress with the right shoes will work, as long as the lingerie underneath exposes her for the naughty woman she is.
Before you can address any physical problem, a thorough psych-social must be done. This is where I ask a series of personal and embarrassing, and provocative questions where the patient is lead to expose herself to me while confessing some of her deep held secrets. I'll ask all about her sexual history, sexual practices, unrealized fantasies, I am going to ask questions on all these topics and more, and she'll answer me because, well, I'm her "Doctor" so she can open up to me, I'm there to help, right? ;-)
I do this in a very professional manner and underneath my stoic presentation I'm delighting in her confessions (and watching her squirm). Next comes the physical examination.
This is where I begin to position and pose her. I might ask her to remove some clothing, or I might ask permission to do that myself. Again, my demeanor is professional and stoic as I begin to comment on her body, possibly taking notes as I go along. Usually I'll put on a pair of vinyl/medial gloves and I'll touch various parts of her body and ask for feedback when I do. This is how I'll learn where she is the most sensitive and responsive. It is the perfect way to establish sexual communication without trying. Nothing like having her spread her legs and parting her labia so I can get a better look. I might turn her over on her stomach, or on all fours, where I will part her cheeks to examine her anus. Closely. I'll also use lubricant and then probe her orifices to determine everything is as it should be. Now it comes time for the medical instruments.
I'm not much of a speculum or enema guy, so I prefer to use dildos, vibrators and the like as medical instruments. Vacuum pumps can be very effective too. And what I do with those is related to what her presenting problem was/is. The idea is, of course, to get her so worked up she'll do anything I want. Then the nice, concerned doctor becomes the Dominant, perverted doctor who's going to "take advantage" of his female "patient" to satisfy his pervy desires. The prescribed course of treatment is how I will satisfy my own urges. Often times I might prescribe she increase her sperm intake, it will amaze you to know how many women don't get enough sperm in their diet, and I'm happy to help them lead a healthier life, so this allows us to continue her treatments.