A hydrocele happens when fluid collects within the scrotum. The scrotum is a sac (pouch) of skin that hangs below the base of the penis and contains the testicles (two oval-shaped male organs). Hydroceles are common in newborn babies, especially premature babies, but they can also happen in older kids and adult males.

Hydroceles are usually painless for babies. They typically go away by the first birthday. If a hydrocele doesn't go away or gets more swollen, a simple surgery can treat it.

Here's how to care for your child.

• Follow your healthcare provider's advice about any follow-up visits.
• Watch the hydrocele for any changes, and let your healthcare provider know if you notice any.

• The swollen area is getting bigger.
• Your baby seems to be in pain.

How does a hydrocele happen? Before a male is born, their testicles develop in the belly, then travel through a "tunnel" into the scrotum. Normally, this tunnel later closes. When this tunnel doesn't close properly, fluid can leak into the scrotum. This results in a hydrocele.

If the tunnel remains open (called a "communicating hydrocele"), fluid from the abdomen can travel up and down the open tube, making the hydrocele change in size. If the opening in the tube is large enough, a hernia (when some of the intestines travel into the scrotum through the tube) can also develop.

Are there other types of hydroceles? When the tube closes, trapping the fluid in the scrotum, it creates a "noncommunicating hydrocele."

What is the treatment for a hydrocele? Babies with a hydrocele don't usually need any treatment since the hydrocele isn't likely to cause pain and often will go away on its own. If it doesn't go away by itself, or if a hernia develops with the hydrocele, surgery can fix it. Older kids and teens with a hydrocele usually need surgery to repair it since it can cause discomfort and is less likely to go away on its own.