As far as the lactulose is concerned...In my opinion, this is the most important thing you can do for your baby. Lactulose helps push the toxins out of the body and should therefore be given directly after meals. The amount of lactulose should depend on stool consistency. On lactulose, your baby's stool should be soft (difficult to pick up), not firm, and not diarrhea. Your vet should be able to help you determine how much to start out at, and then increase or decrease as needed.
Supplements...Denosyl(Sam-E) and Milk thistle help with liver function. They have antioxidants which help protect the liver from further damage. Also those two supplements help repair the already damaged parts of the liver. Denosyl should be given on an empty stomach, and the pill should not be crushed or broken because if it is, it loses its effectiveness and it's as good as not giving it at all.
With my baby, he did not have an operable shunt, they went in for exploratory surgery and were not able to find it...So they treat him as if he has MVD. He's doing really well. We cook a special homemade diet for him and give him lactulose and several supplements. I'm really happy to see him doing so well. He was diagnosed when he was around 9 months, I think, and he just had his 3rd birthday