Great post! This kind of situation plays a big part in what I like now (though disliked at the time) about some of the medical experiences that form the basis of my fetish.
For several years during my adolescence, I was part of a program that included visits to a large hospital where I was examined and tested by a number of different doctors and staff people in a number of different rooms throughout the complex. These were long visits, taking a big chunk of a day with lots of waiting in between test stations and lots of getting in and out of clothes as needed.
Because I was one of a fairly big number of kids doing this program, and because it was a regular enough event that staff got to know us, there evolved a semi-relaxed atmosphere around the whole thing that was surreal in some ways but it was obviously supposed to put everyone at ease.
They had a large main waiting room where parents could hang out. TV, table full of bagels and muffins and coffee, etc. Even stacks of games for the kids during long waits. We would go in and out of there during these long visits to be seen by various people for various parts of the process.
Parents would be called back for conferences and updates with the main supervising doctors as well as for other reasons. Parents were ALLOWED to be present for any part of the visit, but they would usually give us privacy.
There were a number of times when my parents popped in unexpectedly and saw me but one of the times that I remember well is somewhat similar to what you describe here.
There were a number of doctors involved with the program, each for his or her own reason according his or her special area of expertise and research (this was through a large children's hospital and medical school), but each of those doctors, whatever their main focus, was supposed to meet with us individually and that usually involved them giving us a physical exam, no matter how many of those we'd already had, in addition to performing or supervising whatever test fell under their personal specialty.
So, anyway, at one of these big visits when I was 14, I was wrapping up for the day, exhausted and arms covered in bandaids from multiple blood samples. I had changed back into my street clothes (usually, upon arrival at these visits, they made us change into either hospital pajamas or into our gym clothes and we stayed like that all day, taking the shirt or even all of it off periodically, depending on what was being done). I was taken back to a large-ish, semi-L-shaped-room that was a conference type room at the front and an exam room at the back, around the corner. Most of the exam area was visible from the conference area as the exam table was center of that area rather than being against a wall.
A pair of doctors met with me and spoke with me briefly, and then, as usual, announced that they were brining my parents in and that I could sit over by the door while the doctors and my parents sat at the table, and I heard one of the doctors say "Dr. So-and-So needs to have a quick look at him." Then he looked at me and said, "I know you just got dressed, but you are going to get a real quick examination before you go. You can leave your underpants on, but take off the rest of your clothes and just put them on the chair next to you."
So, I sat there in my underpants for a bit, then the other doctor came in. He motioned for me to follow him around the corner and my dad made some crack to me about "boy, you're having a long day of it."
The exam was pretty much the standard check up. Underpants came down briefly both when I was laying down and then again while I was standing up. When he was done, he thanked me and my parents and the other doctors and left and I was told I could get dressed.