What Is Hydrocele

A hydrocele is a urological condition characterised by the abnormal collection of serous (clear watery) fluid around the testis in the scrotum.^1,2 They are common in newborns and infants assigned male at birth (AMAB).³ The prevalence of hydrocoele in newborns  is 6%, compared to 1% in adults.⁴

Hydrocoeles are typically caused by persistent open processus vaginalis or an imbalance between fluid secretion and absorption within the tunica vaginalis.^5,6  While the scrotum is the most common site for hydroceles, they can also develop in the external genitalia and pelvic regions.⁵ 

Hydrocoeles are mostly asymptomatic but they can manifest as a painless swelling in one or both testicles. Typically, the swelling resolves on its own by the age of 1-2 years, and further complications are rare.^2,7 They are harmless but may cause discomfort or become painful if increased in size. Hydroceles are usually left untreated, especially if they are small and are not causing significant symptoms. This approach is adopted as the risk of recurrence and post-surgical complications are higher compared to the potential benefits of surgery.^3,8,9 

Overview

The gubernaculum is a fibromuscular structure that is connected to the lower part of the gonads (the primary reproductive organs) and grows down towards the groyne area during foetal development.¹⁰ 

In people AMAB, this growth is influenced by the androgen hormones and continues into the scrotum, carrying with it the gonads (testis).^11,12 In people Assigned Female at birth(AFAB), the absence of androgen hormones stops the growth of the gubernaculum, thereby leaving the gonads (ovaries) in the pelvis and eventually, developing into the ovarian suspensory ligament and the round ligament.¹³ 

The processus vaginalis is an out-pouch part of the internal abdominal wall covering. It creates a passageway for the gubernaculum to grow downwards and carry the gonads, after which it degenerates, usually after birth.^10,14 Of the 80-90% of babies born AMAB with the processus vaginalis still open, only about 25-40% still have it unsealed by two years of age.¹ 

Following the descent of the testis, the processus vaginalis forms the tunica vaginalis, a two-layered protective covering of the testis with a miniscule amount of fluid in between both layers.^15,16 The inner layer of the tunica vaginalis covers the testis and spermatic cord; while the outer part lines the internal surface of the scrotum; and a lubricant secreted by the tunica vaginalis in between the inner and outer layers enables the testis to move freely within the scrotum.

Types of hydroceles

There are two types of hydroceles.^1,3,14,17

Primary or communicating hydrocele

Here, the processus vaginalis remains open thus providing a connection between the peritoneum (abdomen) and tunica vaginalis. Depending on which part of the processus vaginalis remained open, a primary hydrocele can be further subdivided into:

1. Congenital hydrocele: 

The processus vaginalis is patent and communicates with the peritoneal cavity allowing fluid to enter the tunica vaginalis, however, the opening is too small for abdominal contents to enter (in which case it becomes an inguinal hernia).

2. Infantile hydrocele: 

The processus vaginalis closes at the level of the deep inguinal ring but remains open below it and allows fluid accumulation.

3. Encysted hydrocoele:

Both the inner and outer parts of the processus vaginalis are closed while the central portion remains open, and fluid accumulates within it.

4. Vaginal hydrocele: 

The processus vaginalis remains open only around the testes.

Secondary or non communicating hydrocele:

Here, the processus vaginalis has closed but an underlying condition causes excess fluid production or interferes with the fluid drainage in the tunica vaginalis. Causes include infection (filariasis, tuberculosis of the epididymis, syphilis), injury (trauma, post-herniorrhaphy complication), or cancer.

Causes of hydrocele

There are four ways hydroceles can occur.^1,5

• Connection with the peritoneal (abdominal) cavity through the persistent open processus vaginalis. This is the commonest cause in newborns.
• Excessive production of fluid.
• Defective absorption of fluid. 
• Obstruction of the lymphatic drainage of scrotal structures. This is the commonest cause in adult men. 

Management and treatment 

The management of hydrocele depends on various factors.¹⁸

• If the hydrocele is due to an underlying cause (such as testicular torsion, testicular cancer, epididymo-orchitis, trauma, or varicocele surgery), an emergency referral is requested for specialist care
• If there is no underlying cause, the patient is reassured and advised on scrotal support (such as the use of supportive underwear)
• If the hydrocele is large or symptomatic, the patient is referred to a urologist or paediatric surgeon, depending on clinical judgement
• If treatment is decided, approaches to repair include surgical plication; excision and eversion; and needle aspiration¹

Diagnosis of hydrocele

The diagnosis of hydrocele is mainly clinical (medical history and physical examination) but may also involve further investigations.^1,18

Your doctor will likely take an in-depth medical history about the swelling in the scrotum and groyne or a sense of the scrotum feeling heavy. There will usually be no pain though it can occur especially if the swelling increases in size. There may be fluctuations in the size of the testicle as it may be smaller in the morning and larger later in the day. The doctor will ask for current and previous sexual history, history of trauma, previous abdominal or pelvic surgery, and presence of associated symptoms (such as nausea, vomiting, abdominal pain, urethral discharge, and weight loss) which may point to a different diagnosis.

During physical examination, a transillumination test is done. This entails shining a light through the scrotum to determine if fluid is present in the scrotum. The test is positive if the scrotum allows light transmission, implying the presence of fluid. A haematocele  may transilluminate faintly. 

The test is negative if the light will not shine through the scrotum and implies the scrotal swelling is due to a solid mass (such as cancer). Next, the doctor will examine the scrotum and inguinal region to assess the position of the swelling in relation to the testis, the consistency and texture of the swelling, testis size, the presence of lymph node swelling, the severity of testicular pain, and whether the swelling is actually a hernia. 

If there is significant scrotal swelling, diagnosis is confirmed with a scrotal ultrasound, which will also help determine the cause. If there is any co-existing medical condition, other investigations will be done such as urine and blood samples and abdominal ultrasound.

Risk factors

Risk factors in newborns and infants include sex, premature delivery, breech presentation of babies, low birth weight, and cryptorchidism (late descent of the testis). For adults, risk factors include scrotal or testicular injury, ischaemia, inflammation, surgery, and sexually transmitted infection.^1,3,17

Complications

Complications include:

• Recurrence of the hydrocele
• Infection
• Pyocele (purulent fluid in the scrotum)
• Haematocele (blood-filled scrotal swelling)
• Testicular atrophy (shrinkage due to obstruction of blood flow)
• Infertility
• Rupture of the hydrocele
• Hernia of hydrocele 
• Psychological effects (depression)¹ 

FAQs

How can I prevent hydrocele?

Hydroceles in newborns cannot be prevented since they occur during foetal development.¹⁹ In adults, hydroceles can be prevented by practices such as

1. Avoiding minimising the exposure of the scrotum to traumatic events
2. Safe sexual practices to reduce the risk of contracting sexually transmitted infections

How common is a hydrocele?

The prevalence in newborns is 6% while in adults, it is about 1%. About 80-90% of newborns AMAB have a patent processus vaginalis, however only about 25-40% still have it open by two years of age 

When should I see a doctor?

You should see your doctor if you or your child:

1. Has swelling of the scrotum, especially if it has not resolved spontaneously after the first year of life
2. Has sudden pain or swelling in the scrotum

Summary

A hydrocele is a urological condition characterised by the abnormal collection of serous (clear watery) fluid around the testis in the scrotum. They are common in male newborns and infants. Hydroceles are caused by persistent open processus vaginalis or an imbalance of fluid secretion and absorption within the tunica vaginalis. Hydroceles are mostly asymptomatic but may present as painless swelling of one or both testicles which usually disappear by 1-2 years of age with no complications. The diagnosis of hydrocele is mainly clinical (medical history and physical examination) but may also involve investigations such as ultrasound of the scrotum and urinalysis. 

Hydroceles cannot be prevented in children because they occur during the foetal development. In adults, they can be prevented by safe sexual practices and avoiding events that cause trauma to the scrotum. You should see a doctor if you or your child has swelling of the scrotum, especially if it has not resolved spontaneously after the first year of life or if you or your child has sudden pain or swelling in the scrotum.