The best way to treat a poisoned cat is make it vomit. Secondly see the label of poison to know what type of poison it is. If you feel that poison has started effecting nervous system and cat is becoming unconscious then take it to vet immediately. Symptoms of kidney failure are excessive urination and vomiting. In addition to this your cat must look like depressed and listless. Most important thing in this case is; try to get maximum fluid into cat to minimize dehydration. A visit to vet is must.