Epididymitis is where a tube (the epididymis) at the back of your testicles becomes painful and swollen.
The main symptom of epididymitis is pain and swelling in 1 or both testicles.
Epididymitis is usually caused by a sexually transmitted infection or urinary tract infection.
Epididymitis is treated with antibiotics. Painkillers and cold packs (or a bag of frozen peas wrapped in a tea towel) can help with the pain.