Susie gives us a very accurate assessment with regard to the "high enema". I've ready just about every text or entry to be found in Google Books, as it relates to enemas. While the best, or most efficient, mechanism to achieve a "high enema" may be debatable or open to opinion, the result seems to be common to most methods. A complete emptying of the large intestine seems to be the ultimate result.
As far as warnings regarding the use of enemas with suspected appendicitis, I think it's fair to say that they should only be used upon medical advice, or in circumstances where medical intervention is immediately available should there be any complications. Most medical texts seem to indicate that enemas, in the presence of an inflamed appendix, may trigger a negative event such as a burst appendix. This may cause the spread of infection beyond the appendix itself. This is usually a serious medical emergency.
Times have changed and access to medical treatment is less problematic than it was years ago. Rather than horseback, a buggy ride, or bumpy trip in an old jalopy, most of us in urbanized areas are relatively close to emergency treatment in times of calamity.
Enemas are an old time treatment for modern day maladies. Doctors seldom prescribe their use anymore. Some of us discovered the pleasures and efficiency of this simple procedure and aren't likely to forego their use for any reason imaginable. That includes the best reason of all: an enema just makes us feel better at times.
I too, didn't get discharged after an appendectomy, until I could urinate and have a BM at the hospital. I was catheterized more than once to empty my bladder, and eventually had an enema to jump start my bowels. I've posted previously about my mom scolding the medical staff for keeping me for extra days due to a lack of a BM. She admonished them several times to "just give him an enema". They eventually complied with her requests and I was out the door shortly thereafter. I got a few more after returning home. My mom just couldn't let the issue go and told many others that she had to fight with the staff to give me an enema.