Gabby had early stage CRI. My vet wanted me to put her on canned Purina NF but not only did she hate the food, I read that low protein can cause muscle wasting in senior cats and I didn't want to reduce her quality of life. I fed her high quality, low phosphorus foods and her kidney values did not change at all in the two years I had left with her (she passed away from cancer unrelated to her CRI).
Some low phosphorus foods that are good are Wellness Turkey, PetGuard Chicken & Beef, EVO 95% Chicken & Turkey, and Merricks' Before Grain Beef & Turkey, Blue Wilderness Duck. These all use higher end ingredients which are easier on the kidneys. The Wellness, PetGuard, and EVO can all be purchased in larger 13oz cans if money is an issue, making them about the same price or cheaper than Fancy Feast.
Here's a link to a more updated food chart with premium foods. Make sure you use this or Tanya's charts to compare phosphorus levels, because the Binky chart is very out of date and some foods listed as low phosphorus on that chart now have very high phosphorus levels.
https://docs.google.com/leaf?id=0B8...MzhkYTkxOGM4NThk&sort=name&layout=list&num=50
Hydration and low phosphorus is key to managing CRI or CRF. Mix some water in with her food so that she's getting as hydrated as possible. If she's not picky with food yet, you're in a good spot and there's no need to panic. CRI is so common with senior cats it's good to do a kidney friendly diet with senior kitties anyways.