Does your dog have any other ailments? Dark spots internally?Tumors? Lumps? How old are they? Any water issues? Anyone else in home sick? Bile could mean infection as well but other things possible.
My last lab once had issue with not eating for days and vet eventually said he was dying due to dark tumor they spotted with detailed tests. We took him home against their wishes after they said we should let him go…. and on fifth day they said he had hours left and I turned to chinese herbal treatment as last resort. Yunnan Baiyao is what we discovered and for whatever reason we gave him the red pill followed by the remaining dose of the regular for a week. A few days later he started eating again and a week later, miraculously he jumping on furniture again and lived another 5 good years to 15. The pill must have stopped some bleeding they did not find and allowed him to heal and eat soon after. Six months later there was no sign of a dark mass anymore too and we gave him that herb on and off for a few months.
Now, I am not saying you should try that but if there is internal bleeding somewhere and they cannot figure it out, the red pill will heal and stop the bleeding almost overnight. They gave those pills to soldiers in wars when they get shot and cannot get back to a surgeon. It was a miracle for us.
Taking them to an alternative vet is not a bad idea as well. Sometimes, you need to solve the issue for your pets on your own. Google helped me find that herb and the reviews were astonishing. Also, visit an alternative herbal dog store as well.
My heart goes out to you while dealing with this. I hope he gets better and you can find something that helps heal him.
https://www.activeherb.com/baiyao/ is where we got it. read the reviews.