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It is hard (impossible) to say whether it is liver shunt or MVD without further testing. There is no surgery for MVD. I know the testing and surgery is expensive but the only place I'd want to have this surgery done would be University of Tennessee followed by Cornell.
Have any tests been done besides the bile acid test?
What were the bile acid results?
What are you feeding?
What supplements are you giving?
What anesthesia was used that he reacted badly to?
By the way, my Yorkie doesn't have a shunt or MVD but does have high bile acids.