Orchitis is a painful swelling of one or both testicles, usually triggered by a viral or bacterial infection. It can start suddenly or build over a day or two, turning a normal day into a careful waddle. The first sign is a deep, heavy ache in the ball. It feels like someone kicked you hours ago, but the throb keeps growing. Red, shiny skin follows. The scrotum on the sore side turns lobster-colored and feels warmer than the other half. Swelling balloons the sac. One testicle may double in size and feel tight, as if the skin is stretched over... Learn more