Hi, I have an anal fistula, already had 4 operations, including a seton and a plug, all unsuccessful. Recently the abscess flared up again, it presented itself on the surface of my skin and burst, I noticed small black particles in the pus, do you know what these black particles are? And should I leave it to drain itself, or go for another operation? Thanks! My apologies, I have no credit card, so cannot pay, did not know I had to pay.