[katts]

Hi
New member, past lurker, long time cat owner.
I'm so desperate to find any answers I can on this issue, because the vets are puzzled. I've done a lot of my own research but I can't find anything on sudden levels this high.

Backstory: My 12(?) year old rescue cat has been healthy, aside from a basal tumor on his neck that was completely removed several years ago.
Late last week I'd noticed he'd lost a bit of weight, but nothing serious, and no behavior changes. This week, I saw that he lost a bit more weight and was unusually lazy, so I immediately took him into the vet to get bloodwork.
Got a shock today:

His urea level is 50 (normally supposed to be 5-12)
Creatinine level is 877 (normally supposed to be 71-203). How is he alive with these levels??

Additional abnormal levels/remarks:
Anion gap is 30 (normally 12-26),
Phosphorus is 2.55 (normally 1.00 to 2.40),
Calc osmality is 346 (normally 285-314)
Mean corp vol is low at 38.8.
Platelet adequate.
3+ Poikilocytosis is present
Marked echinocytosis present.
Marked azotemia
It says there is decreased GFR and t4 ok

Apparently there is no anemia (according to the vet)
The bloodwork also said there might be a possible urinary blockage but the vet seemed to dismiss this possibility.

I know a fair bit about CRF, as I had a senior CRF cat a long time ago, but her levels were nothing like this. The vet mentioned there could have been exposure to a toxic substance, but I have been so careful in never bringing any plants into the house, not using toxic cleaners, etc. Is there something I am missing?

He's currently at the vets overnight, but they're only giving him IV fluids at this point (and additional tests, they got a urine sample). I feel time is quickly running out and I don't want to lose my boy in the process.
Are there any other tests I can do, or something I can mention to the vet to check for?
Any help, anything at all would be so appreciated…