Well, a simple blood test will determine whether it's kidney failure, or kidney issues, or whatever. The only problem is that it is friday evening.
If it is kidney failure you should notice that your cat smells very bad. Also, the cat will urinate all the time (kidneys are not concentrating urine) and will drink allot.
Here's a website devoted to CRF
http://www.felinecrf.com/
Now, having said all that, my cat who is now 18 was supposed to be dead 4 years ago if I listened to my first vet. I was shocked when they told me that she had kidney disease and would die within a year. They wanted to put her on 2 different kinds of meds and of course - sell me their special vet kibble for Kidney Disease.
(I have posted on TERB about this in the past.)
Anyway, long story short - I took her to see a vet who is more into natural treatments for animals (she's a vet btw). Her big thing at the time was diet. Don't feed your cat kibble -EVER. She told me, and I now believe that kibble and processed pet foods will kill your animal. She also said that vets make a ton of money selling drugs and selling vet pet food (something she refuses to do).
She gave me a recipe for home made cat food that is essentially meat (chicken or fish) with some vegetables and greens. No rice, no grains, EVER for a cat. Even if you buy your cat a can of sardines in tomato sauce from Loblaws for 49 cents, it's better than kibble.
I started feeding my cat this recipe and her health improved. Her kidney levels actually got better. (I ended up taking her to the Cat Clinic in Hamilton (after giving up on my Toronto vet) and even they were amazed in looking at her kidney levels.) I now firmly believe that processed pet food, especially kibble is terrible for your animal and will never feed it to them. One, cats can't digest grains, they get metabolized as sugar and stored as fat, and 2, cats get their moisture from their food (being desert animals, they don't have a developed sense of thirst to drink enough.) and kibble has next to no moisture (as opposed to meat which is 60% moisture). Chronic dehydration is the worst thing for kidneys as it will burn them out. Kibble = no moisture = chronic dehydration = kidney issues.
Anyway, my cat is going strong (knock on wood). She's 18 now, her weight is good, her coat is good, etc. For a cat that was supposed to be dead 4 years ago, she's looking pretty good.
With respect to your immediate problem, cats often won't eat or drink when they are under the weather and they will also hide. If it is a kidney issue, they can give her an IV to re-hydrate her. I know people who have cats with CRF that do this at home. However if the cat's kidneys are burnt out, it's sad, but too late.
Worth a shot though.
Good luck.
And never feed your cat kibble - ever. Same with dogs.
http://www.optimumchoices.com/Chronic_Renal_Failure.htm
As far as cat vets go, I like Dr. Obrien at the Cat Clinic in Hamilton. Obrien is one of 3 "Cat Practioners" in Canada. All she does is cats and I must admit, she is a very good vet, very skilled.
www.thecatclinic.ca
There is no place in Toronto like this. The only thing....if you want to take your cat there, you have to INSIST on seeing Obrien when you book, otherwise you get one of the run of the mill vets. There is guy there who is pretty good, but ALL of the other women there are really fucing bitchie and patronizing, especially the one fat dyke (who looks like Rosie O'Donnel). She is to be avoided like the plague. Not only does she clearly have a hate on for men, but she thinks she's so much fucking smarter than you. Ironically, Obrien, (who is the smartest one in the joint) is quite the opposite. She's friendly and approachable and treats you like a human being. She'll talke to you, not down to you.