A hydrocele is a buildup of fluid around a testicle that causes the scrotum to swell. It’s painless in most cases and especially common in newborns, though it can develop in older children and adults too. The fluid collects in a thin sac called the tunica vaginalis, which naturally surrounds each testicle. Most hydroceles in infants resolve on their own within the first year of life, but ones that persist or develop later often need treatment.
How a Hydrocele Forms
Before birth, the testicles descend from the abdomen into the scrotum through a small channel called the processus vaginalis. This channel normally closes after birth, sealing off the scrotum from the abdominal cavity. About 80 to 90% of full-term male infants are born with this channel still open, but in most babies it closes on its own during the first year.
When the channel stays open, fluid from the abdomen can trickle down into the sac around the testicle. This is called a communicating hydrocele because the fluid moves freely between the abdomen and the scrotum. You might notice the swelling changes size throughout the day, getting larger when your child is active or crying and smaller when they’re lying down.
A non-communicating hydrocele happens when the channel has closed but fluid still gets trapped in the sac around the testicle. The body normally produces and reabsorbs small amounts of fluid here, but if reabsorption falls behind, fluid accumulates. This type doesn’t change in size the way a communicating hydrocele does. Non-communicating hydroceles are the more common type in adults.
Causes in Adults
In adults, hydroceles usually develop because of injury or inflammation inside the scrotum rather than an open channel from birth. Autopsy studies show that about 20% of men retain a partially open processus vaginalis into adulthood, though only around 6% ever develop a noticeable hydrocele from it.
Common triggers include:
- Infection: Inflammation of the testicle or the small coiled tube behind it (the epididymis), sometimes caused by a sexually transmitted infection
- Injury: Direct trauma to the scrotum
- Inflammation: Swelling from other causes within the scrotum
In many cases, no specific cause is ever identified. The hydrocele simply develops gradually over weeks or months.
What a Hydrocele Feels Like
The most noticeable sign is a smooth, painless swelling on one side of the scrotum. It often feels like a small water balloon surrounding the testicle. The swelling is usually soft and not tender to the touch, though larger hydroceles can create a feeling of heaviness or discomfort, especially during physical activity.
Pain is uncommon with a simple hydrocele. If you’re experiencing sharp or worsening pain alongside scrotal swelling, that could point to something else, like a hernia, testicular torsion, or an infection, and warrants prompt medical attention.
How It’s Diagnosed
A physical exam is usually enough to identify a hydrocele. One of the simplest and most reliable tests involves shining a light through the scrotum, a technique called transillumination. Because a hydrocele is filled with clear fluid, light passes through it and the swelling glows. A solid mass, like a tumor, blocks the light instead. This quick test helps distinguish between the two.
An ultrasound is often ordered to confirm the diagnosis or rule out other conditions. On ultrasound, a hydrocele appears as a well-defined, fluid-filled space around the testicle, clearly separate from the testicle itself. This imaging also helps determine whether there’s an underlying cause like a hernia, infection, or testicular abnormality.
When Treatment Is Needed
Many hydroceles don’t require any treatment at all. In infants, the standard approach is watchful waiting for the first 12 months, since the channel connecting the abdomen to the scrotum often closes on its own. If a hydrocele appears or persists after 12 months of age, surgery is typically recommended because the channel is unlikely to close without intervention.
In adults, a hydrocele only needs treatment if it causes pain, becomes large enough to make walking uncomfortable, or creates significant self-consciousness. Small, stable hydroceles that don’t bother you can simply be monitored over time.
Surgical Repair
The standard surgery is called a hydrocelectomy, performed under general anesthesia as an outpatient procedure. The surgeon makes a small incision in the scrotum or groin, drains the fluid, and removes the sac that held it. In some cases, the tissue is turned inside out to reduce the chance of fluid re-accumulating. If there’s a communicating hydrocele, the surgeon also closes the open channel between the abdomen and the scrotum. A small drain may be placed temporarily to prevent fluid or blood from building up at the surgical site.
If a hernia is present alongside the hydrocele (which happens frequently with communicating hydroceles), the surgeon can repair both at the same time.
Aspiration and Sclerotherapy
For adults who aren’t good candidates for surgery, needle aspiration is an alternative. A needle is inserted into the hydrocele to drain the fluid. The procedure is quick and doesn’t require general anesthesia, but there’s a significant catch: the fluid usually comes back. In one long-term study, 78% of hydroceles recurred after aspiration alone.
Adding sclerotherapy, where a chemical agent is injected after draining the fluid to irritate and seal the sac lining, improves outcomes considerably. In the same study, recurrence after the first treatment with sclerotherapy dropped to 44%, and patients who underwent a second treatment achieved an overall success rate of 89%. While that’s a meaningful improvement over aspiration alone, surgery still has lower recurrence rates overall and remains the first-line option for most patients.
Recovery After Surgery
Hydrocelectomy is typically a same-day procedure, meaning you go home within hours. Expect swelling and bruising around the scrotum for the first one to two weeks. Wearing supportive underwear and applying ice packs helps manage discomfort during this period. Most people can return to light daily activities within a few days, though strenuous exercise and heavy lifting are generally restricted for two to four weeks to allow proper healing.
A small drain, if placed during surgery, is usually removed at a follow-up visit within the first week. Some temporary swelling at the surgical site is normal and can take several weeks to fully resolve, so the final cosmetic result isn’t immediate. Recurrence after surgical repair is uncommon.