For a new parent, noticing that your baby boy’s scrotum appears swollen can be a source of immediate concern. For an adult man, a gradual, painless enlargement on one side of the scrotum can be equally alarming. In both of these common scenarios, the cause is often a hydrocele. A hydrocele is a benign (non-cancerous) buildup of fluid in the sac that surrounds a testicle. It is crucial to understand that this is a very common condition. In infants, it is a harmless developmental issue that almost always resolves on its own without any treatment. In adults, it is a benign condition that is easily treated with minor surgery if it becomes bothersome. While any scrotal swelling always requires a medical evaluation to ensure a proper diagnosis, a diagnosis of a simple hydrocele should be a cause for reassurance.

A hydrocele is a collection of fluid in the tunica vaginalis, which is a thin pouch or sac that surrounds each testicle. The name comes from the Greek words hydro, meaning “water,” and kele, meaning “tumor” or “swelling” literally, a “watery swelling.”

To understand how a hydrocele forms, it is helpful to use an analogy.

• Think of the testicle as a smooth stone.
• This stone sits inside a perfectly fitted, self-lubricating velvet pouch (the tunica vaginalis).
• This pouch normally contains just a few drops of lubricating “oil” to allow the stone to move freely.
• A hydrocele is what happens when this pouch begins to fill up with an excessive amount of watery fluid.
• This can happen for two main reasons: either the pouch’s own fluid production and drainage system is out of balance, or a separate “pipe” from the abdomen is leaking fluid down into the pouch.
• The result is a painless, water-balloon-like swelling around the testicle.

There are two main types of hydroceles, which have different causes.

1. Communicating Hydrocele: This is the most common type seen in infants. It occurs when a small, tube-like connection between the abdomen and the scrotum fails to close after birth. This allows fluid from the abdominal cavity to drain down into the scrotal sac.
2. Non-communicating Hydrocele: In this type, the connection to the abdomen is closed off properly, but there is an imbalance between the fluid produced and the fluid absorbed by the lining of the scrotal sac. This is the most common type of hydrocele seen in adult men.

In my experience, patients, especially parents of newborn boys are often alarmed by painless scrotal swelling, not realizing it’s a common and usually harmless condition.

The cause of a hydrocele depends on whether it is congenital (in an infant) or acquired (in an adult).

Causes in Infants (Congenital Hydrocele)

During fetal development, the testicles form inside the abdomen and then gradually descend down into the scrotum. They travel through a channel called the processus vaginalis. After the testicles are in place, this channel is supposed to close off completely.

• A communicating hydrocele is caused by the simple failure of this processus vaginalis to seal shut. This leaves a small, open pathway for normal abdominal fluid to travel down into the scrotum.

Causes in Adults (Acquired Hydrocele)

In adult men, a hydrocele can develop for several reasons.

• Idiopathic: In most cases, the cause is unknown. It is believed to develop due to an imbalance in the normal production and absorption of the fluid within the tunica vaginalis.
• Inflammation or Infection: An infection or inflammation of the testicle (orchitis) or the epididymis, the coiled tube behind the testicle (epididymitis), can cause an inflammatory fluid collection.
• Trauma: An injury to the scrotum can cause a reactive hydrocele to form.
• Lymphatic Blockage: In some tropical regions of the world, a parasitic infection called lymphatic filariasis can block the lymphatic drainage of the scrotum, leading to a massive hydrocele.

Clinically, in infants, hydroceles are usually congenital due to an unclosed processus vaginalis allowing fluid to enter the scrotum. In adults, I’ve seen them result from injury, inflammation, or infection.

A hydrocele is a very common condition in newborns. It is a congenital issue, meaning the baby is born with it as a result of a minor developmental variation. It is not contagious and is not inherited. The primary risk factor for a congenital hydrocele is being born prematurely.

In adults, a hydrocele can develop spontaneously for no clear reason, or it can be a reaction to an injury or infection. It is not something you can “catch” from another person.

In my experience, many adult cases are idiopathic, but some are secondary to conditions like epididymitis, orchitis, or even testicular tumors, so I always rule those out during evaluation.

The hallmark sign of a hydrocele is a painless, soft swelling or enlargement of the scrotum, affecting one or both sides.

Key features include:

• The scrotum often feels like a small, smooth, water-filled balloon.
• The swelling is generally not painful, though a very large hydrocele can cause a feeling of heaviness, a dull ache, or general discomfort.
• In a communicating hydrocele (in an infant), the size of the scrotum may fluctuate. It might be smaller in the morning after the baby has been lying down and the fluid has drained back into the abdomen, and larger in the evening after the baby has been active and upright.
• A non-communicating hydrocele typically remains a constant size.

An Important Distinction: Hydrocele vs. Inguinal Hernia

It is very important for a doctor to differentiate a simple hydrocele from an inguinal hernia. In a hernia, the opening of the processus vaginalis is much larger, allowing not just fluid but also a loop of intestine to slide down into the scrotum. An incarcerated hernia (where the intestine gets trapped) is a surgical emergency.

Clinically, I often find that hydroceles are soft, non-tender, and transilluminate well, which helps differentiate them from other scrotal masses.

A hydrocele is usually diagnosed with a simple physical examination by a pediatrician or a urologist.

1. Physical Examination: The doctor will examine the scrotum to assess the size and nature of the swelling. They will check to see if it is soft, if the testicle can be felt normally within the swelling, and if there is any tenderness.
2. Transillumination: This is a classic and very helpful diagnostic maneuver. The doctor will dim the room lights and shine a bright penlight through the back of the swollen scrotum.
   • In a simple hydrocele, the light will pass easily through the clear fluid, causing the entire scrotum to glow a bright red. This confirms that the swelling is a fluid-filled sac.
   • If the swelling is caused by a solid mass, like a hernia or a tumor, the light will not pass through.
3. Scrotal Ultrasound: An ultrasound is the gold standard imaging test to confirm the diagnosis and, most importantly, to evaluate the underlying testicle.
   • An ultrasound is a non-invasive test that uses sound waves to create clear pictures of the scrotum’s contents. It can:
     • Definitively confirm the presence of fluid around the testicle.
     • Provide a clear view of the testicle to ensure that it is healthy and to rule out any other abnormalities, such as a testicular tumor.
     • Help to differentiate a simple hydrocele from a more complex issue like an inguinal hernia.

The treatment for a hydrocele depends entirely on the age of the patient and whether the hydrocele is causing any problems.

Treatment in Infants

For newborn boys with a congenital hydrocele, the recommended treatment is almost always watchful waiting and reassurance.

• Natural Course: In the vast majority of cases (over 90%), the channel connecting the abdomen to the scrotum (the processus vaginalis) will close on its own, and the trapped fluid will be slowly absorbed by the body.
• Timeline: This process typically occurs within the first year of life. No medical or surgical intervention is needed during this time.
• When is Surgery Considered? Surgery is only recommended if the hydrocele:
  • Persists beyond 12 to 18 months of age.
  • Continues to grow very large.
  • Is associated with a definite inguinal hernia.

Treatment in Adults

• Observation: If an adult hydrocele is small and is not causing any pain or discomfort, no treatment is necessary. It is a benign condition that poses no health risk.
• Surgical Repair (Hydrocelectomy): Surgery is the definitive and recommended treatment for adult hydroceles that are large enough to be cosmetically bothersome or to cause a feeling of heaviness and discomfort.
  • The Procedure: A hydrocelectomy is a straightforward outpatient surgical procedure performed by a urologist. The surgeon makes a small incision in the scrotum or the groin, drains the fluid, and then either removes the hydrocele sac or stitches it in such a way that it cannot collect fluid again.
  • Recovery: Recovery is typically quick, with most men returning to normal, non-strenuous activities within a week or two.
• Needle Aspiration: This involves using a needle to drain the fluid from the sac. This procedure is not recommended as a standard treatment because the fluid almost always comes back within a few weeks, and the procedure carries a risk of introducing an infection.

Discovering a swollen scrotum on your baby boy or on yourself can be an unsettling experience. However, a diagnosis of a hydrocele should bring a sense of relief. This common condition is simply a harmless collection of fluid around the testicle. It is not cancer, it is not dangerous, and it does not affect fertility. For parents of newborns, the key is patience, as the vast majority of these congenital hydroceles will disappear on their own within the first year. For adult men, the condition is equally benign. If it becomes large enough to be bothersome, it can be permanently cured with a simple and safe outpatient surgical procedure. Clinically, I emphasize that while hydroceles are not dangerous, persistent or symptomatic ones may require simple surgical intervention for relief and peace of mind.

1. The Urology Care Foundation. (n.d.). What is a Hydrocele? Retrieved from https://www.urologyhealth.org/urology-a-z/h/hydrocele
2. The Mayo Clinic. (2024). Hydrocele. Retrieved from https://www.mayoclinic.org/diseases-conditions/hydrocele/symptoms-causes/syc-20363969
3. The Cleveland Clinic. (2022). Hydrocele. Retrieved from https://my.clevelandclinic.org/health/diseases/16294-hydrocele