I had this moment with a cat of mine. She had a genetic heart disease that cats can get that throws blood clots. The clots can either stop the heart or, as in her case, get stuck in the spinal area and cause paralisys and pain. When that happens the vet only has 2 choices, put the cat to sleep, or try to operate. If they operate the quality of life is extremely low and they only have maybe another year or so to live. She was already in severe pain and if she did the operation she would still be paralized and in daily pain. I had to let her cross the rainbow bridge to meet her brother who had the same thing happen 4 months earlier. Both times I talked about all options and unfortunately life after surgery would have basically been torture for them both. It is a hard stuggle for pet and owner alike.