I thought that was gallstones? I read an article about that just before I had my gall bladder removed.
The coffee reduces gallstones theory is clearly wrong, as I had one big-ass (4 cm diameter) gallstone. Or, if it DID work, that means that I would have had a gallstone the size of a croquet ball otherwise. Wow. That was quite a scary thought.
Crap. Coffee increases your chances of kidney stones.