Sorry about the possible UTI.

I don't know much about UTIs and antibiotics, but I know a thing or two about diet controlled CKD. I wrote a whole thing about raw feeding for senior kitties on the Think Tank forum, but in case raw is not an option, below are some Weruva foods are low carb (<10%)/low phos (<250mg/100 cals). FWIW, I had Ruby on Weruva before I switched to raw, and raw was much better at lowering all of her kidney values, plus she loves it!
Weruva Cats in the Kitchen La Isla Bonita
Weruva Cats in the Kitchen Pates Meowiss Bueller
Weruva Truluxe Glam 'N Punk
Weruva Cats in the Kitchen Fowl Ball can
Weruva Classic Pates Jeopurrdy Licious pouch
Weruva Classic Pates Family Food pouch
Weruva Cats in the Kitchen Pates Cattyshack
BFF PLAY Tuna & Salmon Shhh... pouch
BFF PLAY Tuna & Turkey Totes! pouch
BFF PLAY Tuna & Chicken Chill Out pouch
Weruva Cats in the Kitchen Pates Cat to the Future
Weruva Cats in the Kitchen Pates The Breakfast Cat
Weruva Classic Pates Meal of Fortune
Weruva Cats in the Kitchen Lamburgini
Weruva Cats in the Kitchen Double Dip
Weruva Cats in the Kitchen Funk in the Trunk