The missus had some monster kidney stones (a pair of 'em, almost a cm each!) about a year ago.
She was taking night classes at the community college at the time, and in her cultural differences class (she wants to be an interperator) they had a potluck. So she ate a little of everything, and the next morning her stomach hurt and she was vomiting. I told her it was prolly food poisoning, and had her stay home.
I went to work, and when I called her to see if she was okay at about noon, she was still vomiting. Well, this was obviously serious, so I took off work and we went to the emergency room. Turns out it was kidney stones, and the vomiting was from pain. The poor thing was throwing up from pain for hours /ubbthreads/images/graemlins/icon15.gif /ubbthreads/images/graemlins/icon15.gif!!
3 surguries, a few complications, lots of vicodin, and 2 months later, she's all better. Now the only pain comes from the monster ER bill that medicaid won't cover (we're not actually married, and therefore she's not covered by my insurance - wish she was).
Watching her like that was god-awful, let me tell you. That said, she was a real trooper - I would have been absolutely unbearable to be around if I went through what she did.
The moral of this story? Drink water people, lots and lots of it. As I understand it from everyone I've talked to, kidney stones are about the most painful experience a person can have.