Or rather, it's not in Itzl's blood.
His morning blood test came back clean. His BUN was back in the normal range - high normal, but normal. Hydrating aggressively and keeping him on his medicines will bring it the rest of the way back to mid-normal.
He's also been much happier today, not as fussy. He was even happy to see the people at the vet's when we went back for his blood test this morning.
I'll meet with the vet later to discuss his after care (other than the medicines) and schedule his therapy sessions. Those should provide some interesting pictures.
In the meantime, here's a picture of him resting between jobs:
And a picture of him alerting to a visitor's cell phone: