What's ailing Daisy?

About this time last year we found out that one of Daisy's liver enzymes was too high.  We had x-rays done to rule out cancer, and we started her on injections for arthritis.  She has arthritis, because of an old injury to her hip that happened before she came to us.  Our vet postulated that the inflammation from the arthritis was causing the spike in her liver enzyme.  Daisy didn't much like taking the injections, and they didn't seem help.  We had her liver enzyme level checked a couple of months after starting the injections, and it had climbed even higher.  I stopped giving her the injections at that time, and we decided to get a second opinion from a vet in my husband's hometown.  All our vet knew to do was to keep ordering expensive tests.  After getting a second opinion, we decided to just wait and see if she developed any clinical signs of illness.  She has not acted sick through any of this.  She's nearly ten years old, and she has not slowed down much.  She's still a very active dog.

I took her in for her annual check-up a few weeks ago and had her liver enzymes checked again.  Both of her liver enzymes were high this time, not just one of them.  This means that there is something going on her little body that is causing liver cells to die.  We've had several tests done, and I took  her to see an internal medicine veterinarian.  So far we have determined that Daisy does not have any of the following:
bone cancer (ruled out via x-ray)
lung cancer (ruled out via x-ray)
Cushing's disease (ruled out via low dose dexamethasone suppression test)
liver cancer (ruled out via ultrasound)
gallstones (ruled out via ultrasound)
hyperparathyriodism (ruled out via blood test)
hypo- and hyperthyroidism (ruled out via blood test)

The internal med vet called last night, and she has given us the option to have a liver biopsy done.  It's not cheap - none of this has been cheap - and I really don't want to put a dog with no clinical symptoms through that.  The vet said that her best guess is that Daisy is having a problem with her bile draining too slowly.  We're going to try a medication and see if that helps.  I'll take her back to have her liver enzymes rechecked in 6 weeks.  Sounds like a simple enough plan, but it is just awful trying to get Daisy to take medication.  She has nearly driven me to tears trying to get a pill down her mouth.  She has to take glucosamine and fish oil.  I spent $50 on chewable peanut flavored glucosamine tablets, and she doesn't like them.  We have to grind them up with a mortar and pestal and them mix it with a little bit of Alpo.  The new medication is going to come from a compounding pharmacy.  It will be in liquid form, and they are going to make it "beef" flavored.