Hi my mini schnauzer has Liver Shunt its not as horrible as internet makes out in some cases. It just made me think when you said about walking drunkenly its something he did before treatment. My boy is 9yrs old and is just fine now(touch wood) no real symptoms now on perscript food and lactulose but was treated by my local vet for 2years saying it was irritible bowel!!!!! had full boby MRI normal and bloods normal. I'm sure its probably not this but felt had to mention just incase. I went to a consultation in Leeds said what he thought it was straight away before doing any tests! let us know how things are going, keep pushing the vets x