A hydrocele is a fluid-filled sack along the spermatic cord within the scrotum.

Hydroceles are common in newborn infants.

During normal development, the testicles descend down a tube from the abdomen into the scrotum. Hydroceles result when this tube fails to close. Fluid drains from the abdomen through the open tube. The fluid builds up in the scrotum, where it becomes trapped. This causes the scrotum to become swollen.

Hydroceles normally go away a few months after birth, but their appearance may worry new parents. Occasionally, a hydrocele may be associated with an inguinal hernia.

Hydroceles may also be caused by inflammation or injury of the testicle or epididymis, or by fluid or blood blockage within the spermatic cord. This type of hydrocele is more common in older men.

The main symptom is a painless, swollen testicle , which feels like a water balloon. A hydrocele may occur on one or both sides.

During a physical exam, the doctor usually finds an swollen scrotum that is not tender. Often, the testicle cannot be felt because of the surrounding fluid. The size of the fluid-filled sack can sometimes be increased and decreased by pressure to the abdomen or the scrotum.

If the size of the fluid collection varies, it is more likely to be associated with an inguinal hernia.

Hydroceles can be easily demonstrated by shining a flashlight (transillumination) through the enlarged portion of the scrotum. If the scrotum is full of clear fluid, as in a hydrocele, the scrotum will light up.

An ultrasound may be done to confirm the diagnosis.

Hydroceles are usually not dangerous, and they are usually only treated when they cause discomfort or embarrassment, or if they are large enough to threaten the testicle's blood supply.

One option is to remove the fluid in the scrotum with a needle, a process called aspiration. However, surgery is generally preferred. Aspiration may be the best alternative for people who have certain surgical risks.

Sclerosing (thickening or hardening) medications may be injected after aspiration to close off the opening. This helps prevent the future build up of fluid.

Hydroceles associated with an inguinal hernia should be repaired surgically as quickly as possible. Hydroceles that do not go away on their own over a period of months should be evaluated for possible surgery. A surgical procedure, called a hydrocelectomy, is often performed to correct a hydrocele.

Generally, a simple hydrocele goes away without surgery. If surgery is necessary, it is a simple procedure for a skilled surgeon, and usually has an excellent outcome.

Complications may occur from hydrocele treatment.

Risks related to hydrocele surgery may include:

• Blood clots
• Infection
• Injury to the scrotal tissue or structures

Risks related to aspiration and sclerosing may include:

• Infection
• Fibrosis
• Mild-to-moderate pain in the scrotal area
• Return of the hydrocele

Call for an appointment with your health care provider if you have symptoms of hydrocele (to rule out other causes of a testicle lump).

Acute pain in the scrotum or testicles is a surgical emergency. If enlargement of the scrotum is associated with acute pain, seek medical attention immediately.

Behrman RE. Nelson Textbook of Pediatrics. 17th ed. Philadelphia, Pa: WB Saunders; 2004.

Wein AJ. Campbell - Walsh Urology. 9th ed. St. Louis, Mo: WB Saunders; 2007.