It's always worrying when a cat won't eat. What's the name of the appetite stimulant. Fister tried some called Percictin (sp?), a half twice a day. It helped, at least for a while. Have you tried Royal Canins "Sensitive". That was Fister's favourite. I also gave him the Whiskas pouches wet food. He would only eat the one in Gelé, not in Sauce. I poured a little boiled water in, and would eat it. His issues were not the kidneys though, but his liver.

I hope Grandma will start eating soon. Sending lots of positive thoughts.