I am hearing of more and more pups with these issues....and they often don't have a definitive diagnosis. The only real way to get one is by doing a liver biopsy and many vets don't like to do that right away. My Olivia was a mess last year and her ALT was over 2,000. She is fine now! Here is the thread about her:
http://www.yorkietalk.com/forums/sic...ick-again.html
I have a friend whose Shih Tzu had an ALT over 4,000 recently....she was not sick and was not hospitalized. They treated her with antibiotics and it is coming down.
In Olivia's case, it took three different antibiotics plus, Actigal and Ursodiol. Thankfully she is doing very well now. Her liver enzymes are all normal.
I don't know what caused it but they did suspect it was infectious. There really was nothing around here that she could have gotten in to.
Hope that Liam does as well!