There are a number of red flags.
Some stories are impossible or highly dubious from a physical or physiological point of view. For instance, I know from personal experience that, as an adult, a 2 liter (2 quart) enema is already much. So when I read stories of a 10 year-old child (weighing possibly 30kg?) getting 3 quarts, I don't believe them.
Some stories describe events that violate medical procedure, or legal constraints. Some of the things described would result in a nurse or physician losing their license to practice, or even being prosecuted. I mean, violations of the law do happen, but if they do it too often they will get caught.
At the same time, I'm quite ready to believe stories in which a physician does something that shocks a young patient, without explanations to the patient - because that happened to me. It seems that some physicians subscribe to the idea that it's best not to explain too much to children so that they don't have time to fuss. More generally, parents and other adults are often ready to do unpleasant things or have unplesant things done to children "for their own good" (again, I have real-life examples), and the child has no say. (Classical pose: child pouting, adults smiling condescendently.)
The same applies to stories in which the same person receives a loooong succession of hard blows from spanking instruments - if it were real the buttocks would be bruised or damaged, and such a punishment would fall really out of line with the law.
I'm highly dubious of stories of teenagers accepting to have their rectal temperature taken or suppositories inserted. At that age, they can do it themselves and are likely to revolt if parents, school nurses or whatever went on messing with their anus. (For instance, in my family, as common in France at the time, we only used rectal temperatures, but I started taking my own an an early age, maybe 5. This is not rocket science, there is no reason to have somebody else do it unless special circumstances, such as incapacitation.)
Regarding aunts and grandmothers... Well, when, as a child, I was left at either of my grandparents' places during school vacations, my grandmother would essentially act motherly and take care of me. So I find it plausible if, in a story where a child stays at his or her grandmother's, the grandmother does whatever a mother would do, perhaps in a more old-fashioned way. Same if left for a stay at an aunt's. So, to me it does not bother me that if the mother would normally use an enema, rectal temperature or suppository, an aunt or grandmother would also do so.
What I find harder to believe is granny or aunty coming to give an enema to a child. And neighbours? Oh, the excuse, the neighbour is a nurse! So many stories seem to have a nurse as a neighbour, they must be living all over the place! I bet that in reality, a nurse, when out of her paid job, really does not want to be bothered with nursing (for free, to top it). So unless the nurse was a really really close friend of the family, I don't believe that.
I'm also highly dubious of very long sessions or action that seem ritualized. Parents, nurses etc. have limited time. Our father was often away (and essentially left the handling of the house and children to my mom), and thus mom had limited time to deal with each of us individually. We did not do enemas in our household but I bet that if we did it would have been a rather businesslike event rather than something that would take one hour.
The same applies to stories that involve lavish houses, multiple maids, etc. Seriously, who lives in such settings?