Liver shunt does not have a poor prognosis if surgery is done. It is only in cases where it is not surgically corrected that pups have a shorter life.
Here is a great link about liver shunt and microvascular dysplasia.
http://www.vet.utk.edu/clinical/sacs...2013-04-10.pdf
My Teddy Bear was not diagnosed with a LS until he was approx 8 (he is a rescue so I dont know exact age) and he had surgery in Feb 2013. He is fine now! Here is a link about his diagnosis and surgery:
http://www.yorkietalk.com/forums/sic...ver-shunt.html