It is true that you only need to fill the Sigmoid colon but I think most people split the Coffee-Enema in half because the 2 cup is easier to retain. Also you get twice the benefit out of one Coffee-Enema session. I like to do the full 4 cup Coffee-Enema once in awhile or if I have limited time. A high colon CE does produce some wonderful results so it really is a matter of preference and IMHO not anything you need to adhere to rigorously.