Aw, so sorry. It hurts a lot. We lost our black Lab, Abbym 7 years ago from acute renal failure. She was 7. Before that, we had Hobie who developed cancer in his front right leg/shoulder and the vet wouldn't just amputate, said there was no hope. He was 10. I also lost Patches, our cat, almost at the same time through a tumor. Vet said no surgery would help. I still cry over all of them.
So now I have feral cats and try not to get too close. My avatar is the one we house trained but she got so sick, she turned nasty and attacked us. i opened the door and she left never to be seen again. I have 4 ferals now, 3 that are friendly and 1 who never comes close which is okay with me. If they would leave and find someplace else to live, I'd be fine with it. It wouldn't hurt as much but there won't be any more close pets for us.