The scrotum can swell for many reasons. Possible causes include cancer, testicular torsion (see Penile and Testicular Disorders: Testicular Torsion), inguinal hernia (see Gastrointestinal Emergencies: Inguinal Hernia), epididymitis (see Penile and Testicular Disorders: Epididymitis and Epididymo-orchitis), hydrocele, edema, orchitis, spermatocele, and varicocele.

Hydrocele: A hydocele is a collection of fluid in the membrane that covers each testis. A hydrocele may be present at birth or develop later in life. It is most common after age 40. Usually the cause is unknown. However, the condition occasionally results from a testicular disorder (for example, injury, epididymitis, or cancer).

Usually, a hydrocele does not cause symptoms. It is found as a painless swelling surrounding the testis. Doctors may shine a bright light on the swelling (transillumination) to confirm the diagnosis. Ultrasound examination of the testis is done in unusual instances—for example, in a young man with no apparent cause for the hydrocele. The ultrasound scan may reveal an infection or tumor.

Most hydroceles need no treatment. However, unusually large hydroceles are sometimes removed surgically.

Edema: Edema is fluid retention involving the entire scrotum. Edema may result from salt and water retention or blockage of the flow of lymphatic fluid (see Lymphatic Disorders: Lymphedema). In both cases, men have no pain. Salt and water retention most commonly occurs because of heart failure, kidney failure, or chronic liver disease. Lymphedema results from blockage of lymph fluid most often because of compression of the abdominal or pelvic lymph vessels (for example, by a tumor or infection by certain kinds of parasites).

Doctors usually diagnose the cause of edema based on the man's symptoms and findings from a physical examination. Sometimes blood tests are done to evaluate liver and kidney function. Doctors treat edema by treating the cause.

Orchitis: Infection of the testes (orchitis) is usually caused by a virus, most often mumps. Mumps usually affects children. If a man contracts mumps, the testes can become painful and swollen and may sometimes later shrink and stop working (atrophy). Usually the diagnosis can be determined based on symptoms. Analgesics and cold or warm packs can help relieve pain. Infection usually resolves on its own without causing permanent problems. Sometimes mumps can permanently damage the ability of the testes to produce sperm, but mumps does not usually cause complete infertility unless it affects both testes.

Spermatocele: A spermatocele is a collection of sperm in a sac that develops next to the epididymis. Most spematoceles are painless. While most need no treatment, a spermatocele that becomes large or bothersome can be removed surgically.

Varicocele: Varicocele is the development of varicose veins in the blood vessels that drain the testis. Veins contain valves that prevent blood from flowing backward. Faulty valves can result in a varicocele. Varicoceles usually develop on the left side of the scrotum and may produce no symptoms. Alternatively, varicoceles may cause a sense of fullness and aching and throbbing pain that become bothersome when a man stands. The varicocele feels like a bag of worms if the scrotum is touched when the man is standing. However, the swelling usually disappears and symptoms resolve when he reclines because blood flow to the enlarged veins decreases. Rarely, a varicocele impairs fertility.

If symptoms are severe, doctors may surgically tie off the affected veins.

Last full review/revision October 2008 by Paul D. Lui, MD