A hydrocele is a collection of fluid in a thin sac that surrounds a testicle, causing swelling in the scrotum. It is a common condition, particularly in newborns, and is usually painless and harmless.

How it Develops

The testicles develop in the abdomen during fetal development and descend into the scrotum. Each testicle is accompanied by a sac-like lining from the abdomen. This sac is supposed to close and the fluid within it is absorbed before or shortly after birth. A hydrocele forms when this process is incomplete.

There are two main types:

Congenital (Communicating) Hydrocele: This is the most common type in newborns. The sac-like lining of the abdomen does not close completely, allowing fluid to flow from the abdomen into the scrotum. The swelling may change in size throughout the day—becoming larger with activity or crying, and smaller while lying down. This type usually goes away on its own by age one as the sac closes.

Acquired (Non-communicating) Hydrocele: This type occurs in older boys and men when the sac is already closed, but fluid accumulates due to an imbalance of fluid production and absorption. Causes can include:

Injury or trauma to the scrotum.

Infection or inflammation (e.g., epididymitis).

Tumors, though this is a less common cause.

A side effect of surgery in the area.

Symptoms

The main symptom is a painless, smooth swelling of one or both testicles.

The scrotum may feel heavy.

In communicating hydroceles, the size of the swelling may fluctuate.

There is typically no pain or discomfort unless the hydrocele is very large or associated with another condition.

Diagnosis

A doctor will perform a physical exam and may use the following to confirm a hydrocele and rule out other conditions:

Transillumination: The doctor will shine a light through the scrotum. If it's a hydrocele, the light will pass through the clear fluid, making the scrotum appear translucent.

Ultrasound: An ultrasound scan can confirm the diagnosis, check for any underlying issues like a hernia or tumor, and rule out other causes of scrotal swelling.