My Tibbe had scintigraphy/sono for possible liver shunt but the tests were negative, though the nuclear-radiologist vet and a consult vet at the test and his two regular vets think he has MVD, but didn't recommend putting him through liver-biopsy confirmation now. Started on the new half-hepatic and half-GI-friendly diet, he is back to his usual self and symptom free since beginning it and coming off the Metronidazole.
I hope your little Wilson has great success with his surgery and think you are such a good mommie for having it done. I've read so many threads here and things online that when done early and not when a dog is very, very ill, it is life-transforming for them.
BTW, are you an RN or PA first assist at surgery? Just wondering.