Endometriosis is not a symptom of colon dysfunction. Rather, it may be a precursor to colon dysfunction.
Endometriosis causes internal scarring which often involves the bowel - many times even causing blockages in the bowel or the intestines. The internal scarring may wrap itself around the internal organs and pull them out of position or crowd them in one area. This in turn leads to bowel dysfunction.
I would say that bowel dysfunction is a symptom of Endometriosis.