When a man’s epididymis becomes infected. It can be very painful and be accompanied by swelling and inflammation. Epididymitis can be caused by a sexually transmitted disease such as chlamydia or gonorrhea, but more often it is caused by E. Coli that a man can get by sticking his penis up a partner’s butt without using a condom (being the insertive partner during anal sex). It can also be caused by non-sexual activity. Also, testicular torsion needs to be ruled out because it can present with similar symptoms and unlike epididymis, requires immediate attention and possibly surgery. Epididymis can be contagious, and is treated with antibiotics.