a couple possible ways
okay, from what i gather (and I'm sure there are other ways,) here are two points that could have contributed (and I'm not saying that it was HW, however I disagreed with people who weren't DB to say that it definitely wasn't.)
1. the cleanse can sometimes cause parasites to scatter. It's not a real big issue for most folks, but there are some horror stories on the board about it. There's a chance that the parasites could have scattered into this area and somehow disrupted something, causing the trigger.
2. DB said that he wasn't having regular bowel movements during the HW (and quite possibly before?) so the toxins weren't being removed from his system. Instead of his body being handicapped somewhat but dealing with the parasites in a way it knew how to, these toxins were recycled and the body then had to deal with the problem in a new way-- this could have caused a general stress on the body that caused the trigger, or it could have pushed toxins somewhere around the spine causing a more specific trigger.
I'm not an expert, this is just what I've gleaned from hanging around CZ and the HW forum specifically.
BMs are SOOOOOO important, in everyday life but ESPECIALLY during ANY cleanse.