Torsion of the testicle is the twisting of the spermatic cord which cuts off blood supply to the testicle and surrounding structures in the scrotum. It is often caused by inadequate connective tissue in the scrotum, trauma to the scrotum, strenuous exercise, or has no obvious cause. Symptoms include sudden severe pain, swelling on one side, nausea, vomiting, light-headedness, blood in semen, or a testicular lump. Treatment involves surgical intervention within 6 hours of diagnosis to untwist the testicle, with one testicle sometimes requiring anchoring to prevent future risk. Prevention focuses on avoiding trauma, though some cases cannot be prevented.