Definitely get a bile acid test. I'm pretty sure ALT levels can be off for many reasons. A bile acid test will better pinpoint if it is livershunt or not. I'm sorry you and Rainbow are going through this
I hope it turns out to be nothing
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.