Hi,
I just went through this 3 weeks ago with Bella. I had her pre spay bloodwork done and her levels came back slightly elevated. So my vet suggested doing the bile acid test and checked her urine for crystals and I had to leave her at the vet all day long. It was excruciating for me and her both. Well her levels came back perfectly normal with 1 slightly elevated again so my vet called someone who is a specialist regarding Liver Shunts in Dogs and they said she was all clear and her levels were actually perfectly normal. My vet was just being overprotective (which I adore)!!
So in all it took 4 days with the results and now I know I have a perfectly happy, healthy, recently spayed Yorkie.
Good luck!