Yes, this! In previous fasts I believed that autolysis would take care of any bowel residue, as Shelton states. However yesterday (Day 5) I was feeling horrible: nauseous, weak, general malaise... and I decided I would do an enema to try to help my body along. I had the same experience as you, with some really foul crap being expelled. OMG I felt almost instant relief! No more nausea, I feel invigorated, and my body is now asking for much more water than it had been the past couple days. I have completely changed my attitude on enemas during fasting.