Can an intestinal obstruction cause Diarreah?? I've been having terrible constipation even with Miralax (polyethylene glycol) and now Diarreah but it's pure water??

Post obstructive di? The obstruction causes constipation, but once the treatments work (& the obstruction resolves) often patients experience post-obstructive diarrhea. The body adjusts to relief by producing excess fluid & moving fluid through faster for a period of time before it adjusts to the new normal. If your symptoms persist, however, see a doctor. It may be something different or serious.