Causes of epididymitis include: STIs. Gonorrhea and chlamydia are the most common causes of epididymitis in young, sexually active males. Other infections. Bacteria from a urinary tract or prostate infection might spread from the infected site to the epididymis. Also, viral infections, such as the mumps virus, can result in epididymitis. Urine in the epididymis. This condition occurs when urine flows backward into the epididymis, causing chemical irritation. It may be the result of heavy lifting or straining. Trauma. A groin injury can cause epididymitis. Tuberculosis. Rarely, epididymitis can be caused by tuberculosis infection