You are right, rustycat, bloodwork will only start to indicate kidney damage when the kidneys are quite severly damaged. Urine tests are a much better indication of how well the kidneys are functioning.
You may be on to something, Stacer, if something scared Angus while he was using the box, he may not feel comfortable using it again.
Cat maid to:
Puddles, female Himalayan (16 yrs)
Jasper, male Ragdoll ?? (approx 9 yrs)
Sweet Pea, female silver tabby DSH (approx 7 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 6 yrs)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey