I was wondering if your dog has or has had a fever at all?
What made you bring him to the vet in the first place?
The baytril can actually cause the liver enzymes to increase.
I do not think bactrim is a good choice either as that medication is not recommended in patients with liver problems.
I would not just randomly treat him.
Your best bet is to have an ultrasound done and then a ultrasound guided biopsy done at the same time. This will give you the most answers. I would do this as soon as you can.
It will tell you if it is cancer or inflammation.
I also think a bile acid test may be helpful. This is a blood test that helps determine if the gall bladder, bile duct, and liver are performing as they should. It is an easy test.
I would also tun a tick titer blood test to make sure it is not Lyme's, Rocky Mountain Spotted Fever, or Erlichiosis.
For antibiotics, I would use Meteronadazole and clindamycin or a cephalosporin for now. If they took a biopsy they could also take a culture of the liver tissue to see if they could culture bacteria from it. If they did, they could see what antibiotics it was resistant and sensitive too.
The milk thistle is more for hepatic toxicity like poisoning. It would not hurt.
If it is chronic active hepatitis he will need to be on medication for the rest of his life to help the liver cells function and last longer.
There is no point in treating it as hepatitis if it is cancer. You need to have a biopsy done to figure out which one it is.
The reason it does not seem infectious is the normal white blood cell count.
If you are short on money, instead of sending out tick titers, try doxycycline 10mg/kg for a few days. If it is a tick disease you should see a rapid improvement.
It would not hurt him at all if you treated him for chronic hepatitis.
Treatment for chronic hepatits:
Vitamin E 10 IU daily
SamE you already know that one
Zinc This is for fibrosis of the liver. We don't know if he has that so hold off on this for now.
Prednisone You will have to get this from your vet
Ursodeoxycholic Acid This protects the liver cells and is an antioxidant. Helps with gall stones and acute hepatotoxicity. You would have to get it from your vet.
I am not sure why he responded to the sulfa antibiotic and not the baytril. The baytril is less harsh on the liver cells too! If he had an infectious hepatitis I would expect to see a high white count. Maybe the white count would be higher now?
That ultrasound is expensive where you live.
By the way, run a urinalysis too if you have not and see if there is bilirubin in it.
http://www.veterinarypartner.com/Content.plx?P=A&A=1779 milk thistle
If his gums are pale then he could be anemic. That would go along with both cancer and chronic hepatitis.
This is the problem I see. Lets say you do the ultrasound and it is cancer. Then what? Are you going to do chemotherapy at $1000-$2000 a month or have part of the liver removed? Probably not right? Maybe it is a type of cancer that can not be treated. Will it drive you crazy if you don't know for sure if it is hepatitis or cancer?
That is why the ultrasound is so expensive, because the specialist is doing it right? It should be a little over half that if a regular vet did it.
Maybe what you could do then is antibiotics, prednisone, pepcid and samE. When he refuses to eat and drink, can not get up and around, loses bowel or bladder control, can't breathe well, or has bad vomiting or diarrhea then it is time. That is what I would do. I have never had good results with cancer and chemotherapy. I would not do it on my own dog.