I am sorry you are dealing with this. If it is a shunt, it is fixable! Try to think positive. I know it is scary, but hopefully he can just have the surgery and be fine. One of my pups just had LS surgery this past Feb. and he is doing well....here is Teddy Bear's thread:
http://www.yorkietalk.com/forums/sic...ver-shunt.html
I like this link about liver shunts:
ACVS - Portosystemic Shunts (PSS)
I also highly recommend that you seek out a board certified surgeon for this surgery...I think you did mention a specialist.
I will keep you and your Yogi in my thoughts and prayers. I hope if you read Teddy Bear's thread it might give you some comfort. He did amazingly well after the surgery. It really was not as bad as I had thought it would be for him.