I am so sorry for your loss and the cruel way your vet handled the entire situation. These 2 websites might help you understand acute juvenille renal failure. Yorkies are prone to this disease. I never had a Yorkie with this so I won't be much help.
http://www.geocities.com/Vienna/Opera/2167/
Guide to Hereditary and Congenital Diseases in Dogs
http://www.dogbiz.com/dogbiz-genetic-disease-guide.html