Testicular swelling, like pain in the testicle, can arise from several different causes, some of which constitute a medical emergency. Testicular swelling may be perceived when there is localized enlargement of a testicle or a more generalized enlargement of the scrotum. It may be one-sided or bilateral and may or may not be accompanied by pain and other symptoms. Swollen testicles or swelling of the scrotum can result from testicular torsion, a medical emergency. Testicular torsion is a condition in which the testicle twists inside the scrotum, causing an interruption in the blood supply to the testicle. Testicular torsion is an emergency, since interruption of the blood supply can lead to tissue death of the affected testicle. Inflammation of the testicle (orchitis) or epididymis due to any cause can also lead to testicular swelling. Other causes include anatomical abnormalities, infections, hernia, and tumors. A hydrocele is a benign buildup of fluid around a testicle that can appear as testicular or scrotal swelling. A varicocele is the enlargement of veins within the scrotum and does not involve the testicles themselves. Testicular cancer is an uncommon cause of swelling in the testicle. When congestive heart failure causes fluid buildup in the lower extremities, it can be so severe as to cause scrotal swelling, although the testicles themselves are not affected.