Yes, there is open pyo (uterus drains fluid) and closed pyo (no drainage at all). Why would her vulva be red if there is no liquid there and the problem is in the uterus? Closed pyo doesn't cause a red or itchy vulva, does it?
I'm just trying to talk you out of being nervous.
Did they do an xray or ultrasound to look at the uterus since you are so concerned?