Help much needed please. I had a fistulotomy on a very low simple fistula 5 days ago. It has been draining some mucus as one would expect, but nothing too bad. The external would hole seems to be ok, a bit bloody, but again nothing too bad. Its kind of hidden within a skin tag. But today I've noticed a pus build-up in the area where the original abscesses kept occurring. This is close to the external hole, but not on it. Now I'm free-falling. Why would there be a pus build-up if the fistula has been laid open. Or is this how they drain?

Hi Missbailey. Are you sure it's puss? If it is you should have some pain and it should be warm on the touch.
My guess is that it is stuff you get with healing, not puss. Keep in mind it takes time - about s month- for a wound to heal post fistulotomy. During that period you still get some white drainage.