Orchitis is an inflammation of 1 or both testicles. It is usually caused by an infection or by bacteria that come via the blood from other parts of the body. Orchitis may be caused by the virus that causes mumps, STDs or other causes. At least one-third of males who contract mumps after puberty often develop orchitis. If both testicles are inflamed, the inflammation and infection may reduce fertility.
Attribution: Straight Talk Foundation