Pat, I'm so sorry to hear this. I was thinking that maybe it's a reaction to the steroids. Since he threw up his food and hasn't eaten very much, this may be causing the diarrhea. I know that pred must be given with food or vomiting may occur and maybe even diarrhea. I don't know what type of steroid he's on though. Yes, I'd definitely call your vet and he may need to be seen. I'll keep him in my thoughts and prayers.