As an adult, exactly once!
I was in Simms position. A tall blonde woman with her hair tied up in a bun and wearing surgical scrubs comes in the room carrying an enema bag that looked about 3 qts, but I had not seen that specific bag before. she's so tall she does not need a step-stool, and she easily hangs it above the bed. As she did, I noticed that she looked very familiar. She was even taller, and larger breasted than I am, but had blonde hair of the same color ant texture I had as a teen.
She reached back onto some sort of tray and picks up this long, straight nozzle that must have been 6-inches long. Then she looks towards the doorway she came in through and says in a voice that is somewhat familiar, "Mom are you sure she is going to trust me, or should you be doing this?" She touches it to my rosebud, and the clock radio comes on! Time to wake up, and get the kids off to school and get to work!
Oh well, this IS what I signed up for. Dreaming about enemas is not.
The only other dream I ever had about enemas was when I was a teen, and I don't remember anything else about it,