i know it's really confusing and scary.. there's a liver shunt group.. you should join, if it weren't for the kind people in that group i wouldn't have gotten through my girls liver shunt scare.. my girl after lots of testing got her liver shunt surgery a little over a month ago. the test your vet recommended you getting, is it the scintography? (liver scan)? ... that is a very necessary test in determining if there is a shunt and how bad it is... skip the ultrasound and go straight to that test... as far as your dog goes, her bile acid numbers are high but not terrible.. my girls pre and post were over 400... the most important thing to do for your dog is to get her on a low protein diet, the vet should have suggested prescription diet L/D.. i know everything is confusing and you feel helpless but don't panic, do your research, join the yahoo group, they'll help you ALOT.. and get your dog on L/D... it's a good thing your dog is young that will make the outcome pretty bright for him/her.. early diagnosis of a liver issue is the key.. good luck and much love to you and your dog.
