Gayle, I had a dog with nearly the identical biopsy results. Everything I do is organic in my yard. I rarely use chemicals in my house, other than the occasional household bleach in laundry. My closest neighbor also gardens organically. There's almost no way my dog could have been repeatedly exposed to toxins or heavy metals in the last however many years.
We ran the cushings test on Grover not once, not twice but three times over a period of about five or so years. Her liver was what the radiologist and internist called "a classic cushings liver." The first test came back borderline/inconclusive. The second, borderline. The third about a year ago finally came back negative. Grovie had an extremely high alkaline phosphate level for the last 1/3 of her life.
The treatment for cushings is dangerous. I balked at treating her with it. We started down this path initially because she seemed to feel bad, was lethargic and something was clearly wrong. I'm not sure how, but it seemed to get better on its own.
Grover was a stray for about 6 months when she was 1-1 1/2 years old. I don't know what happened to her during that time. Perhaps this played a role? I joked that she had liver disease because she was a beer drinker (she used to love to sneak a few sips from my old bf's beers when he wasn't looking.) I joked because it kept me from crying.
The thing is, it IS possible to live with a high Alkaline phosphate level. I recall that you said that Kelly seemed to be feeling fine. I think this is one of those cases where vets want to fix what's wrong when they're not even sure what IS wrong. I spent a lot of time "discussing" (ok, arguing) with my vet what WAS wrong with Grover? And if we weren't sure, why was he suggesting that we treat her with a strong medicine just because senior dogs 'tend to' get Cushings disease?
We started down this path in 11/2001. Grovie passed away in 12/2006...her heart gave out at age 12. During that time, we evaluated very carefully every single medicine she needed -- did she need it badly enough to put extra work on her liver? (And kidneys. The two are so interrelated). Heart medicine, yes. Other medicines, no. Or perhaps yes, but at half strength. It was an excruciating balancing act.
My advice? Follow your instincts. All I had was my gut that told me that a high liver enzyme didn't mean what I was told it meant. Of course, there have been times when I have been certain that my dogs have been sicker than their blood tests have indicated. Like I tell new dog owners -- we know our dogs better than anyone else.
I wish I had really concrete advice for you. But maybe this helps in some tiny way?
Bless you and your seniors.