The rear end is not an entrance it is an exit...
It is like trying to eat with your but and poop out your mouth...
Ever had a colonoscopy???
John Hopkins and other medical schools have been looking at coffee enemas for treating some forms of cancer/lessening the effects of chemo..something with the alkaline in the coffee....and they say it works. Can't remember exactly the reason it works. Even the American Cancer Society said coffee enema trials look promising.