It means he likely has MVD. Drugs given should be carefully thought out forever. Low protein diet may be indicated. He has GI troubles which can go along with MVD. So he will be dietarily tricky but doable.
Bile acids can go up for so janyreasons. Because pre and post were both high it is likely he as an unappy liver. BUT it sounds like he will be fine.
Ellie's pre was worse than that and she is 11. Deep breaths.
I would not open my dog up just for a biopsy in this case.