Aw, sorry to hear that Valient. But if they're operating then they must think he has a good chance of recovering.
CLKD, my girl has kidney disease - it's very common in older cats. But apart from drinking more than normal, she has no symptoms, it was only discovered when she had blood and urine tests and a scan. Eventually she'll have to go on a special diet but the vet said she could last for years!