I rarely give medical advice, but: I do not recommend this.
People have been talking about coffee enemas since the February 8 episode of My Strange Addiction featured a couple that said they're "addicted" to them:
Humans have been colon cleansing since the dawn of time. Doing so with coffee isn't a new thing either. Back in 1982, Dr. Maurice Shils and Mindy Hermann wrote in the Bulletin of the New York Academy of Medicine about cancer trends:
No one has been able to demonstrate the existence of specific "toxins" as a clinical factor in human cancer. Preoccupation with "detoxification" and "purification" has led to the advocacy of coffee and other enemas to cleanse the bowel of toxins.
So, even 30 years ago toxins were a thing. But it goes back further.
The coffee enema is part of the still-popular Gerson therapy, developed in the 1930s. "How the Gerson Therapy Heals" explains the reasoning behind coffee enemas and how they "stimulate the glutathione-S-transferase system by 700%" and "cleanse the blood." It says the enema route is essential because "patients cannot be expected to consume the therapeutically necessary daily amount of at least one liter of coffee by drinking it." (Although that was written in 1990. A liter is 33 ounces, and now we have Starbucks' 30-ounce trenta.)