This is a very interesting question for me. I started my journey in kink as a 8 or 9 year old. I discovered my moms enema bag and intrinsically knew how to use it. Use it I did.
Way back in second grade a manhood test was to staple one's thumb with a stapler. Manhood tests were things boys torture each other with to prove sufficient toxic masculinity had been obtained. Physical prowess, disgusting things, withstanding pain, anti social and criminal activity.
Well, Steveo came up with a much better test then staples! HO and N gauge trains were something my dad liked and justified because ‘the boy likes them’. Take the wires to the rails off the rail and place them on the manhood applicant. Fingers or arms. As the inventor naturally I was the operator too.
Somehow I never gave other boys enemas - strange how societal norms are wordlessly passed down. Girls you ask? Dr. Steve at your service! (WEG) Sadly just 3 girls before puberty, but enough to cement a lifelong kink.
Take that background throw in a few healthy helpings of trauma, bake at 350 for a few years and bingo! Sexual sadist.
A sexual sadist isn't cruel to be cruel but thrives on delivering sensations to partners and relishes the reaction. Is an enema painful? Is it pleasurable? Is it unique? Yes. Do all three outcomes have reactions? Why, yes, yes I believe so.
Does a sexual sadist like to spank with or without implements? Does a sexual sadist like to use electricity for all sorts of delightful activity? Does a sexual sadist like to tickle bound or unbound people? Does a sexual sadist like to lovingly bathe their partner after doing terrible and and delightful things to her? Could one go on? Yes.
Unsaid in the literature, in general is the fact that in general a sadist gives the finest aftercare in the BDSM spectrum because, quite frankly the sadist needs aftercare just as much their partner does.
The enema has a uniquely powerful effect - it is humiliating, it induces submission, it removes agency - the ability to control one's course - ceding control over deification is quite a right side act (left side/right side S/m D/s M/s the top, dom act is the left, the bottom, sub act is the right) and taking that control is pretty right side.
Enemas can sit by themselves as a discrete activity. Enemas can be part of the constellation of MedFet. Enemas can be part of BDSM. Enemas don't have to be part of BDSM, they are independent elements.
Does this enema enthusiast like BDSM? Yes.
Great post. Which is why preferring to give to oneself is not BDSM.