What Causes Enlarged Inflammatory Nodes And Peri Anal Swelling?

I have a peri anal swelling below left labia measuring 10mm X 5mm as per the ultra sonography done. It also says that there is evidence of hypoechoic S shaped tract like structure in perineum on the left side of introus. The ends of tract are slightly bulbous and measures 10mm X 5mm. The deeper end of S shows minimal fluid. The are enlarged inflammatory nodes in neighbouring area. What can this be? When I pass Stools there is a cutting pain and the stool is mucous filled and loose.