You didn't say why your vet is against a shunt repair. It really is not a difficult surgery and would certainly be the way I would go. Your pup is at a high risk for bladder stones...did your vet discuss that with you? He would then have to have surgery to remove them. Unless your pup is a high risk candidate and has other severe health issues, I would personally get a second opinion...and probably from a board certified specialist. Either internal med or surgical.....see what they think.
Here is a thread about my Teddy Bear who had a liver shunt a few years ago. He was estimated to be 8 or 9 at the time.
http://www.yorkietalk.com/forums/sic...ver-shunt.html