The first DRE I remember having I was about 10ish. I had stomach pains, and since my sister recently had appendicitis, Mom thought it prudent to take me to the ER.
I remember stripping to my underwear. and waiting on the table. (This is the only time my father, as well as my mother, were in the room with me being examined) Since I was 10, they took my temp orally. (Something I never liked. I have very narrow nasal passages, and it is difficult to breathe right and hold the thermometer in my mouth.)
The ER doc asked all the pertinent questions, then had me lie back and he stethed and palpated my belly. While doing the palpation, he reached below the waistband of my underwear and palpated the lower abdomen. He then had me pull my underwear down to just below my knees and roll over on my left side in the Sims position. (Of course, I didn't know the name or what he was going to do at the time.) He then did the DRE.
It was not my appendix, (Which I still have 40 years later) but acute constipation. He prescribed some suppositories.
Oddly, the most embarrassing thing about the whole incident was when we got home and Dad gave me the first suppository, teaching me at the same time to administer them t myself.
After that, I don't ever remember having a DRE until I went into the Navy, where they were a standard part of every physical.