For me: a diverticulitis flareup & diagnosis. How I used to laugh (weakly) at the old SNL skits...but that HURT! I thought I had ripped my abdomen or something!
Again, though, it's one of those ailments you can largely control with diet. No clue as to why I have it- I've always been happy eating my greens & grains, so roughage is not an issue for me.
Funny thing is, though, that if you're having a flareup, roughage is the last thing you want. It exacerbates the irritation connected to the bacterial infection, giving them more of your body to work with. That's what happened to me- I had been on a nearly vegetarian diet for about 3 days when I had my first (and so far, last) flareup.