Could really use some vibes

My mom's cat, Chrissy, is a appx a 16 year old siamese that has lost 3 pounds in the past year. She's getting blood work and urinalysis on Friday if she makes it that long. She's down to 5 lbs. She has no prior known health issues except the sudden decline in appetite. Vet will determine root cause on follow up, scheduled Friday. Suspects kidney failure due to family history (another from the same litter has FLUTD, and another from the same litter passed from a urinary blockage over a holiday weekend in a rural town) but it may also be diabetes. She's not blocked, she's going wee fine. Mom and I can't quite remember what year they were born. Either way, she is elderly and the kindest action will probably be putting her down. It's tough. I saw her being born, along with her litter mates. The momma gave birth on my bed. (icky, but one of my most cherished memories growing up) She has always been somewhat neurotic but a darling cat.

Appreciate any kind thoughts, and appreciate having somewhere to let this out. Thanks.

Oh bless her little heart   Lots of mega healthy  coming her way, and please keep us updated?

Many, many that it's something treatable and she'll be with you for quite some time to come.

Loads of vibes for this precious, sweet kitty :heart3:

Mom called me last night to let me know Chrissy's appetite is returning. Vet results were promising and his instincts were on point, her kidney panels are somewhat off normal and her kidneys are starting to show their age. BUN and creatinine levels were elevated, but weren't as bad as we expected to see. The rest of the panels were within normal limits. He wants to switch them to a lower protein food and recheck in a couple of months to monitor her kidneys. FLUTD/CRF/general kidney/bladder problems run in that feline family.

Some good news, at least. Continued for Chrissy!

I'm confused at the vet's recommendations. I may post this as a separate thread to get more insight but -

I know low protein/phosphorus/magnesium is important for kidney issues.

The vet recommended a food below 22% protein/.5% phosphorus/.3% sodium. I don't even see rX foods that meet this criteria exactly. rX foods get below the .5% phosph. but the lowest I can find protein wise is around 30%. I think AAFCO requires a minimum of .5% phosph in commercial non rX foods and 26% protein?

He did not provide an rX for any food.

How am I supposed to meet this guideline? Hills k/D or Purina NF looks like the closest match, neither of which we were provided a prescription to purchase.

P.s.

This picture isn't such a good quality but is of the 3 geriatric siameses my mommy has proudly taken care of since they were born (The mommy-cat is just not in this specific pic). Furrball is the left most, he was diagnosed with kidney disease at about 4 years old. Chrissy is the middle and is just now showing signs of kidney disease, Tia is the right most. They are all about 16 years old, darling sweet cats that have lived long, full lives.