Bluesman, don't give up on your kitty too soon; although this sounds kidney related, it could also have been brought on by an infection; treating that would alleviate the symptoms to some degree--so really worth investigating.
I can't tell what country you are in, but if you read the CRF info pages or join the support forum (link I sent earlier), you'll see that a lot of very old cats have been brought back for a bit more good time by careful treatment, but that in the UK the cat's person may have to really press for a copy of results and treatment.
You are welcome to PM me after you've seen the vet--I've just had to get informed about old kitty medical stuff at short notice.