What's the highest creatinine and urea your renal cat's ever gotten?

I'm really worried, my cat had a kind of sudden case of renal insufficiency - we had done an ultrasound months prior, but no bloodwork as she just didn't allow the vet to draw blood (very stressed and strong cat) and the ultrasound apparently was normal, but... when my mom returned to the vet with her about 15 days after the ultrasound (I was recovering from surgery so I couldn't go with) having what I think were early symptoms of kidney problems (dark urine/urine with blood, having a hard time peeing, spotting, eating significantly less, feeling more tired than usual), the vet dismissed all of it as being "caused by the anxiety medication" (she was on fluoxetine, we stopped giving it to her after she started getting sick) and "caused by a prior issue on the anal glands" (which is what she was initially taken to the vet for).

That being said: her urea is 755,00 mg/dL, and her creatinine is 22,48 mg/dL, both taken after she was giving 250ml subq fluids twice the day before the vet appointment. After that, she was given subq fluids at the vet, along with medication, and at home we're giving her subq fluids twice a day, per vet orientation. The vet said her results are beyond even what other cats with kidney problems have died at, so I wanted to see what results other cats got, to see if maybe it's not as bad as it seems/if there's any hope. Either way, we'll keep giving her subq fluids to hopefully improve her situation, and are also awaiting vet advice on what other meds she may need (she calls to follow up on vet appointments since it's kind of hard for us to go over to her clinic).