Another visit to the vet with Az yesterday. He is slowly getting thinner and tireder and wobblier. The vet feels that he has probably either got Cushings syndrome or an internal growth - possibly both. That's in addition to his failing back legs, and his knackered heart. The vet I saw has the commendable attitude that the old don't get sick just of old age, but of specific problems that may be treatable - but advised that for a dog with all three problems who is also now terribly thin, there is not a lot more that can be done. He had a blood test a couple of months ago, which showed nothing.
The vet suggested a urine test, which might just indicate something that can be helped for a little while by steroids. I'm doubtful, but I'll take a jamjar of pee in tomorrow anyway. But the vet agreed that as long as Az wants walks and can stand on his own and walk up steps, he's got a quality of life that is more or less acceptable. As the vet said, it's not like this has happened suddenly, Az has had time to adjust to his more limited life. And he does still prance a little, and pull his cheeky face, and wag sometimes.
Maybe a few more weeks wobbling slowly around the hilltop?