My old dog also has very high liver numbers, she is now 12 yrs going on 13 yrs. Back in 2012 her ALT was over 1900 which is way high. Your old girl’s ALT of 139 is not any where near that high so I would not worry too much.
Here is the 2012 thread on her troubles which might help you – viewtopic.php?f=5&t=154763
Also I had some other tests done and they really did not show anything. I ended up giving her SAMe to help her liver and it works well.
I have been giving my old dog the SAMe since fall of 2012 which has helped a lot in lowering the ALT numbers. She is due for another blood check soon, the last one was 2 months ago and the ALT was about 300 if I remember right. She has never acted sick but I am glad her numbers are now 300 and not 1900. I wish her ALT was 139…
So I would not be too concerned about just the ALT numbers unless there is something else going on. I would not feed her Science Diet K/D, there are better low protein foods out there. I do a combo of home cooked and raw for my old dog.
If you are not comfortable with your vet, I would get a second opinion from another vet. I always get a print out of the blood work and keep it in my dog’s file, that way I can show all her records to any vet. It does seem odd that your vet did not want to clean her teeth but now wants to put her under for surgery… if you have concerns, I would get another opinion.
In closing, those numbers do not seem too awfully high to me and I would see another vet, and see what they say.