Sorry to hear that.
Fortunately your cat had a good, comfortable home and was able to live safely to an old age. The poor kitties that are abandoned only live about a year at best.
Your cat was lucky to have you! It still hurts a lot though.
I am so sorry. Last month we had to do the same for our 18 year-old cat. She also had renal failure. This time we had the vet come to the house rather than make that one, awful last trip to her office. It costs a little more but works out the best for everyone.