I had a CKD cat, if you start struggling with his food, weruva intentionally keeps phosphorus low in their foods, which make them very friendly to ckd cats.

Mine was given 6 mths left after his diagnosis and tests were done, and that’s with rx food and stuff. It was expensive and he wouldn’t eat it, so I did a deep dive into literature about ckd and it turns out unlike dogs and humans for whom limited protein is good, cats need protein or they will die much sooner, so the rx diets being low protein are actually not great. You really just need limited phosphorus.

The levels on the core lines and slide and serve lines are good, you can probably find full breakdowns on their website, and certainly by contacting them, though, if those specific ones don’t do so well.

I had him eating those and I got another 6 years out of him instead of 6 months. My vet asked my secret, cuz we got him back up from his skinny boy weight to a slightly chubby 8 lbs! (Very small cat, 6lbs when I got him)

I can’t guarantee it’ll help, but it might be worth trying.