Sorry to hear about kitty.
One thing is that vet may prescribe subcutaneous hydration if things continue to get worse, and while it's SUPER EMOTIONAL to get the hang of (but I don't WANT to stab my cat!), it's honestly not that bad once you get used to it. Basically it's putting a slug of saline under the kitty's skin to help with hydration every few days.
Once I got confident with the injection (fwew), kitty and I used it as a time to snuggle and bond, so it eventually became a special time (and she got a treat after, so she started looking forward to it). It messed up some travel plans (can't just leave a big bowl of food and water out anymore, more difficult to find sitters), but it was worth it for me. In the end, it was her heart starting to go that I had to put her down for, not the kidneys; so just know that this diagnosis is unsettling, but it's NOT a death sentence, ok? *hug*
-- gnat!
Windsor: 2010 S-Works Ruby
Pantysgawn: 2011 S-Works Stumpjumper 29er
Whiz!: 2013 S-Works Crux (Singlespeed)
Boucheron: 2009 S-Works Tricross
Haloumi: 2013 Tern P7i
Kraft: 2009 Singlecross
Gouda: 2005 Electra Betty
Roquefort: 1974 Stella SX-73