Sorry to hear the news Feline. You don't think you do, but quickly realise, when something like this happens, just how much emotionally involved with pets we become and it seems impossible to remain dispassionate about them. Poor English. Sorry.
We were resolved at the time, to have to make a decision about Noodle, our tabby (12-13 at the time) who was mauled by a greyhound – that basically mashed her back leg (won't go into details). Long story short, we elected to have the leg amputated, praying that everything would be fine. Turned out it was. She still had spinal, renal and intestine function, and now (she's 15 we think!) is still thudding around on 3 legs, like Long John Silver, and has to claw her way up things.
We know there'll come a 'time' with our pets, but whatever age, it's never nice.
Noodle (below) in: "Take your shot, but I'm-gonna-blink-whatever!" – mode