If your kidney disease cat or dog suddenly loses appetite, perhaps not even sniffing the food, maybe he/she feels nauseous from excess stomach acid.
Slippery elm may help. I have had success with this. I have a cat （JOHNNY）who loses his appetite from time to time and a little while after the slippery elm, my cat will eat himself. Note that the time it takes to give relief seems to take longer sometimes so give it a try and be patient.
I mix the powder from a capsule in about 3ml of water and use a syringe to feed the slurry into my cat’s mouth. Note Johnny doesn’t like me trying to give this to him in his mouth when he doesn’t feel well. I persist because as long as I can get some into him, he will feel better and want to eat again.
I haven’t had to give this often. Maybe just twice so far within the last few months so I’m not sure why he wasn’t feeling well. However, after that, he eats and drinks normally.
Knowing Johnny has chronic kidney disease, I tend to feed less dry cat food and give more canned food with water added. He likes it, luckily.
Pet Health Remedies 