Vet refuses to review ultrasound for rx?

Has anyone heard of this? My senior pup had an ultrasound for his abdomen to confirm chronic hepatitis. We went to a specialist for it, who sent the results and the recommendation of “medical management” for his treatment plan. My primary vet refuses to do anything without the specialist’s ultrasound as the radiologist did not put an exact prescription and dosage in the treatment recommendation. My primary has 3 years of my dog’s bloodwork and has seen him regularly, hence the radiologist referral.

Anyone had an ultrasound and the primary won’t do anything? Why would the radiologist need to put “the exact dosage of the exact rx to give him”?

I am so confused.