When fine needle aspirate won't work, or just doesn't seem appropriate, then the choices are ultrasound guided biopsy and surgical biopsy. I am comfortable with surgical biopsy and have no problems taking this approach but ultrasound guided biopsy can eliminate the need for an incision the resultant healing and recovery time. It is best to have biopsies examined by a pathologist and evaluated for copper accumulation, too. If there is only enough tissue for histopath examination the pathologist can estimate the amount of copper with special staining procedures. If you opt not to have a biopsy done then you have to make some educated guesses about what is best.
Zinc supplementation is reported to help some dogs, as well.
I am not sure if there is any research to support this, though. I really do think that a biopsy would be the best approach for most dogs in Jammer's age range due to the potential need for life long medications and the potential for starting the most appropriate medications as early as possible. My vet wants a radiologist to do an ultrasound, needle biopsy on the liver this Thur. RTV- A needle biopsy is an invasive procedure. I think that a mucosal bleeding time test, which can be done in the vet's office, is a reasonable choice for this test but some vets prefer to do more complex testing done through a reference lab.