Purina has a new kidney diet, called "NF early care". It has moderate protein, and slightly reduced phosphorus, for the early stages of kidney failure.
Miss Kitty seems to like it ok, so for now we are sticking with it.
At this point, the only sign of renal failure are her immense water consumption and the increased BUN (blood urea nitrogen). No nausea yet.
Hopefully, the food will help to keep the disease at bay a little longer.