Each testis is suspended in the scrotum on a spermatic cord, which contains blood vessels and the vas deferens (the tube that carries sperm from each testis). In testicular torsion, the testis rotates, causing the spermatic cord to become twisted.
This restricts the blood supply to the testis and causes pain. The condition usually affects only one testis and sometimes occurs after strenuous activity, but may develop for no apparent reason.
Symptoms usually appear suddenly and, as well as pain in the scrotum, may include swelling of the testis, redness of the scrotum, nausea, and vomiting.
This is a medical emergency and without prompt treatment, the testis may be permanently damaged. Treatment is with surgery.