Within the realm of enema fantasies, I had the opportunity for the real thing in the late '90s. Amanda Wildfyre (now retired) was a Minneapolis Domme who specialized in enemas, as well as lots and lots of other kinks. Some of her videos are still available.
She set up an inverted enema session for me. I was on my back, on the floor, naked. She attached weight-bearing ankle cuffs to me and then to a steel spreader bar. My wrists were cuffed and clipped together. Her third floor (of two floors) play space was the upper floor of a classic Victorian home, which had most of the ceiling removed, opening it to the former attic. She had an electric hoist attached to an upper beam, and lowered the hook down to attach it to a cable connected to each end of the spreader bar. Using a push-button tether control, she slowly lifted me off the floor until my crotch was a her eye-level. My wrists were then connected to ropes tied to floor rings, putting me in an inverted "X.".
Her "enema delivery system" consisted of a tank (@ 3 quarts, I think) she filled with very warm, soapy water. The tank was connected to an in-line pump (a repurposed marine pump, gifted to her from another sub) with a positive push-button switch. She then connected the latex tube to the pump and the tubing to a DBC, which she inserted and inflated - after filling the line with enema. Amanda left me in that position for a few minutes to contemplate my fate and to engage in a bit of teasing arousal.
There was a bit of ceremoniousness as she strode over to the pump control and raised her hand to begin the injection. The enema was administered in short bursts, interspersed with more teasing and paddle swats on my ass. I took about 2+ quarts before she decided to release me, but I had to retain it for a few minutes first. I was carefully lowered down after my wrists were released so I could "catch" myself, but still had to wait while the ankle cuffs were released and I was helped up, DBC still in place.
Amanda's medical play area included a toilet in an open area, about 10' away, to which I had to waddle before the balloons were deflated and I was allowed to release.
That was one of three enemas that day. The others were administered in her classic birthing chair and strapped to a spanking bench.
It was a "bucket list" experience, for sure! I would repeat it, but doubt I will encounter another facility so well equipped.
NOTE: those who knew, or knew of Amanda, also know this is not a made-up story. Like only a few others, she was famously smart, extremely kinky, extraordinarily well equipped, and utterly fearless. This session was, for her practice, pretty tame. I know of several Friday through Sunday marathon sessions that incorporated 4 - 6 enemas/day and had at least four+ Dommes (24/7 in shifts) to regulate sleep, nourishment, vital signs, fluid intake/output, etc. Others here may have their own stories about her.