In one of the books on MH website talks of this. It describes someones kidney tubes actually being able to be snapped during the autopsy.
I think this is the reason why my grandfather died... on the farm he grew up on there was very hard well water. He grew up on the farm, and eventually took it over... he spent his whole life there. He also died at 47 years old of kidney failure. There were other reasons too I am sure... but this seemed to play a very large part.