Liver Shunts are not only hereditary and passed down from birth. They can also be acquired later on in life.
A liver shunt is a blood vessel that carries blood around the liver instead of carrying blood through the liver. A liver shunt problem is mostly congenital. A dog may also acquire multiple small shunts from a severe liver disease, such as cirrhosis. There are basically two kinds of liver shunt conditions that are possible – congenital liver shunt and acquired liver shunt.
http://www.natural-pet-care.com/natu...hunt-for-dogs/
Glad to hear your Yorkie is doing better.