This may be hard to believe but it's absolutely true...
I once went to a walk-in clinic complaining of a lower back ache. After interviewing me, the nurse told me to undress and handed me a gown to put on. I left my underpants on, but they were not your normal tidy-whiteys. These were like bicycle briefs made of the finest smooth cotton/polyester blend, and they hugged my bottom very nicely.
The door opened and the doctor came in -- much to my surprise it was a SHE! She was tall and good-looking, about mid to late thirties with long auburn hair. She examined me pretty thoroughly and then asked me to get up on the exam table and lay on my left side (facing the wall).
Then she positioned me with my uper (right) leg cocked up a bit (I'll never forget the feel of her hand on my thigh, guiding it upwards), and said something I totally did not expect:
"Just lift your hip a little and then relax. I'm going to give you a rectal exam."
Next thing I knew, her fingers had slipped inside the waistband of my briefs and slid them down to mid-thigh. Call me perverted, but that happens to be one of sexiest feelings; better even than being totally naked. To be partially stripped and exposed by a "dominant" woman is just wonderfully erotic!
I was still facing the wall as I heard her unscrew the top of a jar. Seconds later she spread my buttocks apart and then her gloved finger was gently tapping at my back entrance. As her finger slid up inside of me I nearly fainted. I couldn't believe my luck. Here I'd come in with a back-ache and this gorgeous female doctor was practically finger-fucking me. And it was about to get better...
While her finger was still inside of my ass I suddenly felt her other hand stray down along my bare thigh and stroke the outside of my briefs. She was probably just admiring the incredibly smooth material (I got those briefs in Vancouver and have not been able to find any like them in the U.S.), but in my current state it seemed like so much more.
All too quickly it was over, but not before my cock (which thankfully was facing the wall) had stiffened. Her hand moved away and she removed her finger from my bottom. She pulled my underwear back up and then told me I could roll back over. I hesitated and when I finally did I was her eyes flicked down to the bulge in my briefs.
I don't know when I've ever been so embarassed and turned-on at the same time. My memories of those brief (no pun intended) moments alone in the exam room with her have, in the years since then, incited many a fine session of self-pleasuring, usually accompanied my some form of anal penetration.
The end result (damn, another pun!) of her exam was that she didn't find anything unusual, but she took a urine sample from me afterward, and tests showed a tiny bit of blood in it. I later learned that her rather deep and agressive rectal exam may have caused this. (Note: Have your doctor take the urine sample BEFORE putting their finger up insdie you.)
In my case, the blood trace led to my undergoing a cystoscopy -- a procedure in which I found myself toattlay exposed and "in the stirrups." This position may be normal for a woman to find herself in, but it's damned strange feeling if you're a man!
Perhaps I should save that story for another time though...