Hydrocele is a condition where fluid builds up in the sac surrounding one or both testicles, causing the scrotum to swell. Although this painless swelling can be alarming to notice, hydroceles are usually harmless and often disappear without any treatment, especially in babies and young children.

Understanding Hydrocele

A hydrocele happens when watery fluid collects between the layers of tissue that directly surround the testicle inside the scrotum. The scrotum is the pouch of skin behind the penis that holds the testicles. When this fluid accumulates, it creates swelling that may make the scrotum appear larger than normal or feel like a water balloon.^[1]

The thin tissue layers surrounding each testicle are known as the tunica vaginalis. Normally, these layers produce small amounts of fluid to allow the testicle to move smoothly. However, when there is an imbalance between how much fluid is produced and how much is absorbed by the body, a hydrocele forms.^[2]

Hydroceles can affect one side of the scrotum or both sides at the same time. When fluid builds up around both testicles, this is called a bilateral hydrocele. The condition is notably more common in newborn babies, but it can develop at any stage of life, including in older children, teenagers, and adult men.^[8]

How Common Are Hydroceles?

Hydroceles are quite common among newborns. Research shows that about one in every ten baby boys is born with a hydrocele. The good news is that in most infants, the condition resolves on its own without requiring any treatment, usually within the first year or two of life.^[5]

In contrast, hydroceles are much less frequent in adults. Studies indicate that only about one percent of adult men develop this condition. When a hydrocele appears in an older child or adult, it typically happens due to different reasons than in newborns, such as injury or infection in the scrotal area.^[8]

Types of Hydrocele

Medical professionals classify hydroceles into two main categories based on whether the fluid sac has a connection to the abdominal cavity or not. Understanding the type helps doctors predict how the condition might progress and whether it will need treatment.

Communicating Hydrocele

A communicating hydrocele means there is an open pathway between the abdomen and the scrotum. This happens during fetal development when the testicles descend from the abdomen into the scrotum. Normally, a thin membrane called the processus vaginalis forms a tunnel for this descent, and this tunnel should close before or shortly after birth.^[2]

When the processus vaginalis fails to seal properly, abdominal fluid can flow back and forth into the scrotum, creating a hydrocele. In this type, you might notice that the swelling changes in size during the day, becoming larger when the person has been standing or moving around, and smaller in the morning or when lying down.^[8]

Noncommunicating Hydrocele

A noncommunicating hydrocele occurs when the processus vaginalis does close as it should, but some abdominal fluid remains trapped around the testicle in the scrotum. Since there is no ongoing connection to the abdomen, this type of hydrocele typically stays the same size or grows very slowly over time. Noncommunicating hydroceles can be present at birth or may develop many years later without an obvious cause.^[8]

In newborns with this type, the body usually absorbs the trapped fluid naturally within the first couple of years. However, when this type develops in adults, it is more likely to persist and may eventually require medical intervention if it causes discomfort.^[5]

What Causes Hydrocele?

The causes of hydrocele differ depending on whether it develops in an infant or appears later in life. In newborns, the condition is almost always related to normal developmental processes before birth. In older children and adults, hydroceles typically result from injury or other medical conditions affecting the scrotum.^[7]

Hydroceles in Newborns

When a male baby develops in the mother’s womb, the testicles form inside the abdomen. During the seventh month of pregnancy, the testicles travel downward through a canal and into the scrotum. As they make this journey, they bring with them a pouch of the abdominal lining. This pouch normally seals itself before birth, preventing fluid from the abdomen from entering the scrotum.^[5]

If the pouch does not close completely, abdominal fluid can drain down into the scrotum and cause a hydrocele. Even if the pouch does close, sometimes fluid that was already present around the testicle remains trapped. In most cases, a baby’s body naturally reabsorbs this excess fluid during the first year or two of life.^[1]

Hydroceles in Older Children and Adults

When hydroceles develop later in life, they are usually linked to some form of injury or medical condition affecting the scrotum or groin area. An injury to the scrotum or a surgical procedure in that region can disrupt the normal balance of fluid production and absorption, leading to fluid buildup.^[7]

Inflammation or infection of the epididymis (the tube that carries sperm from the testicle) or the testicle itself can also trigger a hydrocele. Infections such as certain parasitic diseases, tuberculosis affecting the reproductive organs, or other bacterial or viral infections may be responsible.^[2]

In rare situations, a hydrocele in an adult man, especially one over the age of 40, may be an early sign of testicular cancer or, very rarely, cancer of the left kidney. This is why it is important for any new swelling in the scrotum to be evaluated by a healthcare provider, even if it causes no pain.^[7]

Risk Factors

Certain circumstances make the development of a hydrocele more likely. Being aware of these risk factors can help individuals and parents recognize when to seek medical evaluation.

Premature birth is a significant risk factor for hydroceles in newborns. Babies born before their full term are more likely to have a hydrocele because their processus vaginalis may not have had enough time to close properly before birth.^[5]

In adults, any trauma or injury to the scrotum increases the risk of developing a hydrocele. This could include sports injuries, accidents, or surgical procedures performed in the groin or scrotal area. Inflammation and infection of the testicles or epididymis also raise the likelihood of fluid accumulation.^[7]

Men who have undergone surgery in the groin region, such as hernia repair, may be at increased risk for developing a hydrocele afterward. The surgical trauma can sometimes interfere with normal fluid drainage in the scrotum, allowing fluid to collect.^[1]

Recognizing the Symptoms

The most noticeable sign of a hydrocele is swelling in the scrotum. This swelling is usually painless, which distinguishes it from other scrotal conditions that may cause pain or tenderness. Many people with a hydrocele do not experience any other symptoms beyond the visible enlargement.^[1]

The swelling may appear on one side of the scrotum or on both sides. When you or your child has a communicating hydrocele, you might observe that the size of the swelling changes throughout the day. It tends to be smaller in the morning after lying down overnight and becomes larger during the day after being upright for several hours.^[5]

Although hydroceles are typically painless, some people do report mild discomfort or a feeling of heaviness in the scrotum, particularly if the hydrocele becomes quite large. This sensation of weight or pressure may be more noticeable when sitting for long periods or during physical activity.^[8]

Other symptoms that may accompany a hydrocele include redness of the scrotal skin, a feeling of pressure at the base of the penis, or general discomfort in the groin area. If swelling increases rapidly or is accompanied by severe pain, this requires immediate medical attention as it may indicate a more serious problem.^[7]

Can Hydroceles Be Prevented?

There is no known way to prevent hydroceles that develop in newborns, as these are part of the natural developmental process that sometimes goes slightly differently for some babies. The formation of congenital hydroceles is not related to anything the mother did or did not do during pregnancy.^[5]

For hydroceles that develop later in life, there are limited prevention strategies because many result from unpredictable factors such as infections or injuries. However, protecting the groin area during sports and physical activities by wearing appropriate protective equipment may help reduce the risk of trauma that could lead to a hydrocele.^[7]

Promptly treating infections of the testicles or epididymis when they occur may help prevent the development of secondary hydroceles. Seeking medical attention for any testicular pain, swelling, or discomfort allows for early diagnosis and treatment of infections before complications develop.

How the Body Normally Functions and What Changes With Hydrocele

To understand what goes wrong in a hydrocele, it helps to know how the testicles and surrounding structures normally work. Each testicle sits inside the scrotum surrounded by several layers of protective tissue. The innermost layers, collectively called the tunica vaginalis, are smooth membranes that allow the testicle to move slightly without friction.^[2]

Under normal circumstances, cells in the tunica vaginalis produce a small amount of lubricating fluid. This fluid serves a purpose similar to oil in a machine, allowing smooth movement. The body maintains a careful balance, continuously producing small amounts of new fluid while absorbing older fluid back into the bloodstream at the same rate. This keeps the amount of fluid constant and minimal.^[2]

In a hydrocele, this balance becomes disrupted. Either the body produces too much fluid, or it fails to absorb the normal amount, or both problems occur together. The result is that fluid accumulates in the space between the tissue layers surrounding the testicle, creating a fluid-filled sac.^[2]

In congenital or communicating hydroceles, there is an additional factor at play. The pathway between the abdomen and scrotum that should have closed remains open. Because the abdominal cavity normally contains fluid, this open connection allows abdominal fluid to flow into the scrotum, adding to the accumulation. When pressure in the abdomen increases during the day from standing and activity, more fluid flows down into the scrotum, explaining why these hydroceles often appear larger in the evening.^[8]

The fluid inside a hydrocele is typically clear and watery, similar to the fluid found elsewhere in the abdominal cavity. It is not pus, and a hydrocele is not an infection, although infections can sometimes trigger the condition. The accumulated fluid puts gentle pressure on the testicle but does not usually harm it. The testicle continues to function normally in most cases, and hydroceles rarely affect fertility or testosterone production.^[8]

However, when a hydrocele becomes very large, it can cause discomfort simply due to its size and weight. A large hydrocele may interfere with daily activities such as walking or sitting comfortably. The stretched skin of the scrotum may feel tight, and the extra weight can create a pulling or heavy sensation.^[7]

In some cases, particularly with communicating hydroceles in infants, the same opening that allows fluid to enter the scrotum can also allow a loop of intestine to slip through, creating an inguinal hernia. This is a more serious condition that requires prompt surgical repair. Signs that a hernia may be developing include a sudden increase in swelling, a firm or hard feeling to the swollen area, and crying or signs of pain in an infant.^[5]