My mom grew up in Indiana but she and my grandparents had nothing but well water, which sounds like a more probable cause, if not genetic. She was my age when hers was taken out, but her parents were far older and both had theirs out at the same time. My grandfather's gall bladder was filled with sand at that point.

I have yet to see how TotBF turned out as I'm still waiting to see it interwoven with the film as it should be, but the animation is very striking. Seeing it in motion will be just as powerful as reading it in the novel, I'm sure.