Usually, the only indication of a hydrocele is a painless swelling of one or both testicles.

Adult men with a hydrocele might experience discomfort from the heaviness of a swollen scrotum. Pain generally increases with the size of the inflammation. Sometimes, the swollen area might be smaller in the morning and larger later in the day.

Baby boys

A hydrocele can develop before birth. Normally, the testicles descend from the developing baby's abdominal cavity into the scrotum. A sac accompanies each testicle, allowing fluid to surround the testicles. Usually, each sac closes and the fluid is absorbed.

Sometimes, the fluid remains after the sac closes (noncommunicating hydrocele). The fluid is usually absorbed gradually within the first year of life. But occasionally, the sac remains open (communicating hydrocele). The sac can change size or if the scrotal sac is compressed, fluid can flow back into the abdomen. Communicating hydroceles are often associated with inguinal hernia.

Older males

A hydrocele can develop as a result of injury or inflammation within the scrotum. Inflammation might be caused by an infection in the testicle or in the small, coiled tube at the back of each testicle (epididymitis).

Most hydroceles are present at birth. At least 5 percent of newborn boys have a hydrocele. Babies who are born prematurely have a higher risk of having a hydrocele.

Risk factors for developing a hydrocele later in life include:

• Injury or inflammation to the scrotum
• Infection, including a sexually transmitted infection (STI)

A hydrocele typically isn't dangerous and usually doesn't affect fertility. But a hydrocele might be associated with an underlying testicular condition that can cause serious complications, including:

• Infection or tumor. Either might reduce sperm production or function.
• Inguinal hernia. The loop of intestine trapped in the abdominal wall can lead to life-threatening complications.