Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
Unfortunately, at the age of 12+ years, the most likely explanation is that the liver mass will be cancerous,
and therefore surgical intervention may not necessarily cure the problem.
The only way I'd suggest going forward with surgery, would be if the chest has been x-rayed and found to be clear of visible cancer spread (metastasis),
and if the ultrasound showed that the tumor appears to be fully removeable,
otherwise, I would not recommend further treatment in this case, and humane euthanasia may be the kindest option.
Is this better done as soon as possible. I only got the news yesterday so it is a bit of a shock but I do not want my dog to be suffering. My vet suggested an answer by tomorrow.
there's really not much reason to delay longer than necessary -- it is unlikely that the situation will improve without aggressive care at this point,
but waiting a few hours until your veterinary clinic opens up is likely to be acceptable, as long as he's not too uncomfortable.
you are very welcome -- I know this is a difficult time, my thoughts are with you.