The protocol is to first get a bile acids test (paired samples around a meal) and if they are high, a Protein C test which will tell you if you are dealing with a shunt or MVD. If the Protein C test is normal, there is no need to get an ultrasound.
Comparative Coagulation -- NYS Animal Health Diagnostic Center
Dr. Center from Cornell is one of the leading experts on liver disease in the country. She developed the bile acids test. Since you are in New York, you could consult with her.