Ok now this sounds weird.... and its from memory, and not making this up.

You need to do a little "googling" for this... BUt france was quite a few years ago giving patients mashed potatoes to help in disolving kidney stones and as i recall were getting good results... also potatoe juice was used.... Be carefull here and do more research... potatoes ar part of the "deadlynightshade" family .

[link to en.wikipedia.org]