Hi Scott-
Wow, I hadn’t heard of these type of stones until now. After reading a little about them, you are absolutely correct. They are extremely rare. Again, sounds like extra fluids and frequent opportunities to urinate are very important with these type of stones also. Here is a link from the Whole Dog Journal that may be of some help, but I’m guessing you may have already seen it: http://www.whole-dog-journal.com/issues/13_6/features/Kidney-Stones-Bladder-Stones_16231-1.html
The article discusses cystine stones more towards the end of it. I hope someone can give you some words of wisdom for your friend. Good luck!
