My first was in the ER during college. I had peed blood one night over the weekend, and the student health center was closed, so to the ER I went. They did a variety of tests (all done with the intern/resident as primary doctor - he kept having to go back to the head doc to check on what was next; he left the room every time he had asked me a few questions, then came back and did the next exam or test). One time he came back and said, " I need to do a rectal exam." He instructed me to bend over the exam table and rest my arms there, and spread my legs a little bit. He didn't really spread my cheeks, just pushed a finger between them until he found the opening and then pushed right on in. It made me feel full but it wasn't uncomfortable. It wasn't particularly exciting either (probably because it was 2am and I was tired of being there, plus he was a guy, not that much older than me, and I'm not into guys), but had it been a female...?
The other time was a few years ago when I found a lump next to my anus, and went to three different doctors to be checked (before having the hemorrhoid removed surgically and successfully). All three, one woman and two men doctors, had me lie on my side with my legs pulled to my chest. All used a very bright light, spread my cheeks wide with both hands, and eventually inserted a finger to feel around and ask me if there was any pain at any point. In each case a female nurse was present. In the first exam, the female stood behind the doctor, did not assist, but had a front row seat view of my ass; of all the places in the room she could have stood, given that she wasn't assisting, she stood right where she could have the best view if she wanted it (I never turned my head to see if she was looking at me). In the second, the nurse was behind a cloth curtain and did not assist and did not see any of the exam. In the third, the nurse assisted; she lubricated the doctor's finger and had her face right up close to my bottom as the doctor explained everything he was looking at and doing with his finger (I did turn my head and look this time, and her gaze was focused right on the bull eye).