[Yorkieluv]

I'm so sorry to hear this...When my yorkie had his vaccines as a pup, he had a very hard time after them...At the time, we did not know about his liver problems...But we did later find out that he has liver shunt/mvd
An extrahepatic portosystemic shunt does require surgery in order for your pup to live a good normal life...If he recovers 100% without aquired shunting and he doesn't have secondary MVD, then he will be able to stop special diet and medications within a few months after surgery...
I'm confused as to why your dog was sent i/d if your vet suspects liver problems. Usually, they send you home with l/d which is specifically for the liver. Read the ingredients of the i/d and make sure it doesn't contain any meat products like chicken or pork or organ meats like liver...Those are high in protein and he should be on low non-animal protein right now until they figure all this out.
The lactulose is super important. Do not miss a dose of that, and it's best to give it directly after meals. His stool needs to be soft, not firm...
I know it seems overwhelming right now, but let's see what the results of the bile acid test are...Take it one step at a time...If it turns out that your baby has a portosystemic shunt, then surgery needs to be done. If it turns out that your baby has microvascular dysplasia (HMD/MVD), then he can live a normal life with his special diet, lactulose, and supplements like milk thistle and denosyl (sam-e).
Usually liver compromised dogs like Royal Canin Hepatic LS 14 much better than Hill's products like the i/d, k/d, l/d, etc. It seems to be more palatable. If your vet doesn't carry it, you can always get a prescription for it from your regular vet and get it at another vet's office or at Banfield....
How old is your little Cody??