I have had two cats who went into kidney failure. It was a long, slow process, during which we could alleviate symptoms and slow it down. By "slow" I mean a couple years.
Orlando had no symptoms. He'd go through phases of not eating much and then a couple days later he'd be back to normal. His bloodwork showed none of the markers that kicked in for Erik and Embla a couple years out. Everything looked fine in an ultrasound earlier this year. That picture was taken two weeks ago.
Last weekend his appetite dropped a lot, but he was drinking and producing output. He was spending more time sleeping in a closet, a new favorite hiding spot. Otherwise he was normal. I consulted my vet, who concurred that I didn't need to rush to the ER, and she saw him Tuesday. He had a bad tooth, it turns out, and she thought that might be the cause, and she ran bloodwork both because he was due and because it was required before oral surgery.
She called yesterday with the lab results and said he was in kidney failure. This was not the long, slow chronic kidney failure with which I was familiar; this was something else. It was possible that he had an infection and that was causing it ("though these numbers are really off the charts"), and on that hope I took him back yesterday (after a long and frustrating search of the house; he did not want to be found). They started him on IV fluids and antibiotics.
This morning he was worse. He could barely stand and wasn't interested in trying. The infection theory was a longshot, my vet said, and even if it were that, treating it would not reverse much of what we were seeing. I went back, held him, and said goodbye. This is always the hard part -- saying goodbye, but also all the self-doubt and what-ifs and did I do enough and am I doing the right thing and... Orlando wasn't fighting it, and I dearly hope I did what's best for him.
I adopted Orlando from Animal Friends in 2012, along with Giovanni of blessed memory. The people at the shelter thought he was about six years old at the time, my vet thought younger, and another vet (more recently) thought older. He had a good (almost) ten years after a rough start in life. That will have to be enough reassurance.