Zane was very affectionate last night and this morning. I'm supposed to hear back from the Vet today.
He has a little arthritis in his hips, and both his heart and liver are a little enlarged.
The vet says that to find out more, he'd have to be ultrasounded, which would involve general anesthesia, which has its own risks on an older cat.
Zane doesn't seem to be in constant pain--perhaps intermittent, which would explain the yowlings--and the anomalies in the blood work were not severe, I'm inclined to adopt a 'watching brief'--to not do anything until/unless he gets worse.
I don't know how old Zane is, exactly. He was a full-grown cat when my late Father got him; he could be as young as 11 or as old as 14, so quality vs. quantity of life is an issue. Putting him under anesthesia has its own dangers, and if they do find something wrong with either his heart or liver, aggressive and invasive procedures (e.g. surgery) might prolong his life, but at what cost?