We've been told our Yorkie has a tumor in his kidney. The vet said they can open him up and check the severity of it, but the last time he did that for our previous dog, he called us, told us she was riddled, and that it would be best to put her down so we followed his advice. She had stopped eating so we knew it was the right decision. But with our Yorkie, he's still happy and fairly active ( he is 12 years old ), so this time we want to just give him the pills he needs and hopefully give him a couple more weeks/months at home. So my question is, (and I know that this is a sensitive one), how do you know when your dog is getting ready to pass away?