Important but somewhat unpleasant info below...
Three days ago: Sunshine's appetite drops off. She only eats about 1/2 of her bowlful. Seems otherwise normal.
Two days ago: Zero appetite. Lazier than normal but seems OK. We figure it's just some kind of tummyache.
Yesterday: Zero appetite. Laziness has given way to lethargy. When I got home from work in the afternoon we resolved to get her to the vet early the next day, and left for the evening church service.
Last night: Got back from church and her hindparts were damp and bloody. Diluted blood on floor and sofa cusions. Very obvious discomfort/distress. Very unhealthy smell. Transported her to 24 hour emergency vet, where she was quickly diagnosed with Pyometra, which I had never heard of. It is a NASTY infection of the uterus. Untreated, the uterus can so fill up with pus that it can burst and cause very rapid death. Even without bursting, the infection can get bad enough to cause shock, kidney problems, or other systemic illness. BAD STUFF! Pretty much the only treatment is spaying right then and there. But it becomes much more complicated than an ordinary spay due to the infection and the steps needed to keep it from spreading, as her uterus is now basically a delicate water balloon full of pus. Like, umm, a $2200 surgery bill kind of "complicated." Ugh.
As I'm writing this, my wife just called me to say that the vet left a message saying Sunshine came through surgery last night OK and is recovering normally. I should be able to take her home tonight after work if things continue to go well.
If you have an un-spayed female, keep an eye on things. This condition is caused by an incomplete expulsion of uterine material during her cycle. It's likelihood increases with age (Sunshine is 6 1/2) and it typically starts a month or two after the end of her cycle. Keep an eye on things for a couple months after her cycles, and get her checked ASAP if things look unusual, as it can go from no symptoms to death in less than 24 hours.
Or, just get her spayed!