http://www.yorkietalk.com/forums/yor...ml#post3910860
Here is a link to another thread on here about a person going through a similar situation as you.
In that link I provide some links to Dr. Tobias a leading expert in the field of Liver Shunt. Dr Tobias is located in Tennessee.
I don't know if your vet is a "specialist" or not in this field, but this disease is one I consider serious, and as such, I would get a second opinion as to best practice course of treatment. That being proper and best diagnostic tests, and if surgery is required a surgeon with plenty of experience in the field of LS surgery.
I know that for me, I'd be headed to the Univ of Tennessee if I had a pup with suspected Liver problems.