15 Month old boxer with High liver ALT

[caidasmom22]

My dog is 15 months old and her ALT is now in the 3000s. Our game plan is to put her on Denamarin again and also Actigall. Perhaps a biopsy. Although both the Vet and I are hesitating doing a biopsy. I am just so lost. Nobody seems to know what could be causing this. She is only 15 months old. Types of food that she has had so far are: Taste of Wild, Solid Gold High Protein, and currently 4health Puppy food. She is currently not on any Flea or tick meds. (She was taking nexguard but we stopped in December) Testing so far: Ultra sound, Bile Acid, Liver function, Tick Born diseases, Lepto. (All of which came back fine) She has also completed dewormers and antibiotics in hopes that it was a Liver Fluke or Bacterial infection. I understand this is very rare. Just hoping that someone somewhere might have advice.