Hi pigeonsheep,
So sorry to hear that you and Dexter are going through this.
My Kira was diagnosed with liver disease last summer so I know the worry.
I imagine that someone here has already mentioned the liver shunt and MVD support group at yahoo but I'll mention it anyway because they've helped me out quite a lot.
Also, their info would be helpful even if he doesn't have a shunt or MVD.
Liver_Shunt_And_MVD_Support : Liver Shunt & MVD/HMD Support
Last week we repeated Kira's liver blood test and her liver enzymes are now in the normal range thanks to a low protien diet. The yahoo group has lots of good info on low protien diets including homemade diets. There's good info for making your own recipes to.
Brodysmom's advice is right on, a bile acid test is important and a protien c test may also be needed.
Good luck
Tracey