If Oliver were mine, I would ask for a referral to a specialist. You can waste a lot of time and money with a vet who isn't experienced with more complicated issues. IMO, all vets today should be familiar with bile acid testing if they treat breeds like Yorkies, Maltese, Cairns, Bichons, Havanese, etc.
The protocol for bile acid testing is on the YTCA website. As I said before, this should be
routinely done on affected breeds like Yorkies even if they are asymptomatic.
http://www.ytca.org/health_CenterQue...xpress2010.pdf
In order to find out what is causing Oliver's urinary problems, you have to start eliminating possible causes. Liver disease is one of them.