I don't know much about acute kidney failure except that it is 100% reversible, unlike Chronic which gets worse over time
Lesa, I have been reading everything I can find about kidney failure. Like Mark has said, acute kidney failure is 100% reversible provided it is caught in time.
I'm certain that you caught it in time. Nobody is more aware of their animals behavior than you. Once you saw that Purdey was not well, you took action. I have no doubt that Purdey will survive.
It appears that most likely rapid onset of this is from poisoning. Anti-freeze is a know source and appears to be the common poison cats and dogs get into. All it takes is a car that has leaked from it's radiator and the kitty laps up the water or walks through the spill then licks their paw. Easter Lilies are another poison. I wonder if any of your neighbors recently planted any of their left over Easter Lilies in their garden and that Purdey took a little nibble?
Hopefully by tomorrow morning Purdey will have greatly improved with having the drip all night long.
You and Purdey and Wellington are all in my thoughts and prayers.
Hugs