Here is one of the best articles written about liver disease, and will help you understand what they might be looking for:
http://www.vet.utk.edu/clinical/sacs...NAL-201304.pdf
I know how stressful it must be for you, but try to stay calm as you proceed with whatever tests are necessary to diagnose the problem and establish a treatment plan.
I went through this when Tiki was 7 months old, and had an ultrasound, which did not show a shunt (however, they don't always show up). I declined a biopsy, because the only purpose of that would be to confirm if she had MVD, which would be treated with medical management, diet and supplements. We chose to treat her "as if" MVD was present, and she is now almost 7 years old and doing just fine as long as we don't feed her to much protein or fat.