Can you take Lacy to a vet school for a second opinion? Most vets, even specialists, don't know that much about liver disease.
Ultrasounds are only 80% accurate in diagnosing shunts according to Dr. Tobias (University of Tennessee) and as low as 60% according to Dr. Center (Cornell). What Lacy need is a scintigraphy for an accurate diagnosis.
Did you know that Yorkies are 36 times more likely to have a liver shunt than all other breeds combined? Dr. Center recommends that all Yorkie puppies have a bile acids test before even going to their new home.
Here are a couple of good articles from UT and Dr. Center:
Hepatic Vascular Disorders - WSAVA 2006 Congress The Univ. of TN College of Veterinary Medicine - Portosystemic Shunts