Female young cat sick after getting spaded?

Did they run bloodwork on her before the surgery? Are her kidneys really failing or is she just very dehydrated? They can go into kidney failure from their blood pressure dropping too low while anesthetized. It is very important to check with your vet that all surgical patients have an IV catheter, IV fluids, are intubated, kept warm during surgery, and that vitals such as blood pressure, heartrate, and O2 levels are monitored throughout the procedure. Pain medication before and after surgery is a MUST. This is NOT common if these simple yet vital protocols are in place-- I would question how the procedure was performed.

some cats have underlying illness and the stress from spaying or neutering can bring those illnesses out. i work at an animal shelter and have seen animals get sick/have to be put down/die after being altered. its not uncommon at all.