[Rhetts_mama]

Hi and welcome to YT. I'm sorry that your baby is doing poorly.

It would be unusual to have an active infection with a normal CBC. They would normally see a spike in the white blood cell count. (I'm not saying it doesn't happen, just that it's unusual). Unless the renal failure gets under control, you are probably going to have more issues with dehydration since the kidneys lose their ability to concentrate the urine.

Have you seen received a referral to a specialist? There are lots of potential causes for elevated BUN levels, including, not limited to infection, inflammation, fever, starvation, increased protein intakes, over-exercising, post-renal obstructions, upper gastrointestinal hemorrhage, autoimmune disease, medications as well as kidney failure.