Thanks Jen, no, I was not told that I had a redundant colon. I've actually only had constipation problems since December of 2006. Still, I can't help but think that the extra length of my colon, even if it's not redundant, is playing a role in my symptoms. Why it would have just started to cause issues last December, I have no idea, although my doctor thinks my turning 40 had something to do with it.
Thanks very much for the magnesium citrate suggestion. Fortunately the last couple of days have gone by pretty pleasantly on the miralax/fiber, with at least one fairly normal sized movement per day, but I would love to have some of that other stuff available if things get rough again. I will check with my doctor on the feasibility of that.