oh, hey, I just did this last month! to me it felt like someone had twined their fingers in my intestines near my bellybutton/right rib and *twisted*, hard. For about 12 hours. It was throbbing at the same beat as my pulse. I thought I might have appendicitis, which was what propelled me into the ER, whereupon I was poked, prodded, tested and informed that there was nothing wrong with me.

Dr. Intertubes, however, strongly supported a possible gallstones theory, which you may take for whatever it may be worth. As for me, I'm making vague attempts to eat a low-fat diet and hoping for the best.