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Condition

Hydrocele

Hydrocele explained: real causes, how it is diagnosed, and evidence-based treatment options — with sources, not guesswork.

Also known as: hydrocoele, scrotal hydrocele

Symptoms6 listed
ICD-10N43.3
TreatableYes
DE
Medically reviewed by Dr. Elif Yılmaz, MD, FECSM
Last reviewed 22 July 2026
✓ Clinician reviewed
Hydrocele✓ Clinician-reviewed information
Key takeaways
  • A hydrocele is a collection of fluid between the layers of tissue surrounding the testicle, most often causing painless swelling on one side of the scrotum.
  • In adults in most developed healthcare settings, no specific cause is found in many cases (idiopathic), with infection, injury, or prior surgery accounting for a further meaningful proportion.
  • Globally, lymphatic filariasis — a parasitic infection endemic in 72 countries — remains the leading cause of hydrocele worldwide, affecting tens of millions of men, a fact worth knowing for anyone with relevant travel or residence history.
  • A hydrocele itself is benign, but because it can sit alongside or obscure a more serious problem — including, rarely, a testicular tumour — a scrotal ultrasound is a standard, important part of proper assessment.
  • Not every hydrocele needs treatment; small, symptom-free hydroceles are often simply monitored, and treatment — whether aspiration or surgery — is generally reserved for cases causing discomfort, cosmetic concern, or an underlying cause that needs addressing.

Overview

A hydrocele is a build-up of fluid around the testicle. A thin sac normally holds a small amount of fluid there, made and reabsorbed in balance. A hydrocele forms when that balance is upset — too much fluid is made, too little is reabsorbed, or both. The result is the classic sign: painless swelling of the scrotum. It is one of the more common reasons men are sent for a scrotal scan. It is also almost always harmless, though a proper check still matters.

There are two basic kinds. A communicating hydrocele has an open channel between the belly and the scrotum that did not close as it should. Fluid can move back and forth, so the swelling often changes size with activity or position. This is the classic pattern in babies, and most infant hydroceles clear on their own in the first year. A non-communicating hydrocele has no such channel. The fluid is simply trapped around the testicle. This is the type that more often appears later, in adults.

In adult men, especially with good access to care, many hydroceles have no clear cause and are called idiopathic. That is a normal result, not a sign something was missed. When a cause is found, it is often inflammation or injury in the scrotum: an infection, an injury, or a complication after certain groin or scrotal surgery. Less often, a hydrocele forms in reaction to an underlying testicular tumour. The tumour does not need to be large for this to happen, which is one key reason a scan matters more than an exam alone.

It is worth knowing, for an international reader, that this picture reflects wealthier healthcare settings. Worldwide, the leading cause is different and much bigger: lymphatic filariasis, a parasite spread by mosquitoes. It is still found in 72 countries, and tens of millions of men live with it. Hydrocele is one of its recognised long-term effects. This matters for anyone who has spent significant time in an affected region, and it is worth mentioning to a doctor, since it is managed a little differently.

One useful sign is that a hydrocele lets light through. A torch held against the scrotum in a dark room makes it glow, which helps tell fluid from solid tissue. But this test alone cannot rule out a problem hiding behind the fluid. That is why a scrotal ultrasound is a standard part of a proper check — it looks at the testicle directly. Treatment is guided by size and symptoms, not by presence alone. Small, painless hydroceles are often just watched. When treatment is chosen, options include draining the fluid (sometimes with a sealing agent) and surgical repair.

A hydrocele can sit around and effectively obscure a testicle that also has its own separate issue, including, rarely, a tumour — which is why scrotal ultrasound is considered a standard, important part of proper assessment rather than an excessive step.

Types of hydrocele

Communicating
Caused by a persistently open processus vaginalis, allowing fluid to pass between the abdomen and scrotum; classically seen in infants, and typically changes size with position or activity in adulthood.
Non-communicating (simple/acquired)
Fluid is locally trapped around the testicle with no connection to the abdominal cavity; the typical pattern in adult-onset hydrocele.
Idiopathic
No specific cause identified despite assessment; common in adults, particularly in higher-income healthcare settings.
Secondary (reactive)
Develops in response to an identifiable cause, including infection, trauma, prior surgery, or, less commonly, an underlying testicular tumour.
Filarial
Caused by chronic lymphatic filariasis infection; the leading global cause of hydrocele where the infection is endemic.
How common is it?
In Sweden, a large national registry study found the annual incidence of men seeking specialist care for hydrocele or spermatocele to be approximately 100 per 100,000 men, with treatment incidence around 17 per 100,000 per year and peak incidence between ages 65 and 84. Globally, the picture is shaped by lymphatic filariasis, endemic in 72 countries, with an estimated 850 million people living at risk as of 2021 and tens of millions currently affected.
Source: pubmed.ncbi.nlm.nih.gov

Symptoms

Painless swelling of the scrotum, typically on one side, though bilateral hydroceles occur
A feeling of heaviness or a dragging sensation, particularly with larger hydroceles
Swelling that may change size depending on time of day or activity, particularly in communicating hydroceles
A smooth, generally non-tender swelling that transilluminates (glows) when a light is shone against it in a dark room
Discomfort or cosmetic concern with larger hydroceles, rather than sharp pain
Occasionally, mild aching, though significant pain is atypical and warrants prompt evaluation for another cause

Causes

Idiopathic (no specific cause found), particularly common in adult-onset cases
A persistently open processus vaginalis (communicating hydrocele)
Infection or inflammation, including epididymitis
Trauma or injury to the scrotum
Prior scrotal or inguinal surgery, including some varicocele or hernia repairs
Lymphatic filariasis, the leading global cause where endemic
Reactive response to an underlying testicular tumour (uncommon, but a recognised association)
Radiotherapy affecting the pelvic or groin region, in some cases

Risk factors

Older age (incidence rises with age, peaking around 65–84 in available population data)
Residence in, or significant time spent in, a region where lymphatic filariasis is endemic
Prior scrotal or groin surgery or trauma
Recent or recurrent genital or urinary tract infection
A known testicular mass or tumour (as a cause of secondary hydrocele)

How it is diagnosed

Diagnosis starts with a physical examination and history, including how the swelling developed, whether it is painful, and any relevant history of infection, trauma, surgery, or travel to or residence in a filariasis-endemic region. Transillumination — shining a light against the scrotum in a darkened room — is a simple bedside test that helps distinguish a fluid-filled hydrocele from solid tissue, since fluid characteristically glows while solid tissue does not.

Scrotal ultrasound is considered a standard, important part of proper assessment, since it allows direct visualisation of the testicle itself, separate from the surrounding fluid, and helps rule out an underlying mass that a hydrocele can obscure on examination alone. Where relevant history suggests filariasis, specific blood testing may be used to confirm it. If a testicular mass is suspected on ultrasound, tumour marker blood tests (AFP, beta-hCG, LDH) are typically added.

When to see a doctor
  • You notice new scrotal swelling, even if it is painless
  • The swelling is growing rapidly, or has become painful, red, or warm to the touch
  • You notice a hard area or lump distinct from the general swelling
  • You have fever or other signs of infection alongside the swelling
  • You have a relevant travel or residence history in a filariasis-endemic region and notice scrotal or limb swelling
Reducing your risk
  • Prompt treatment of genital or urinary tract infections may reduce the risk of infection-related hydrocele
  • Being aware of hydrocele as a recognised, generally manageable complication of certain scrotal surgeries, and discussing this risk with your surgeon beforehand where relevant
  • In regions where lymphatic filariasis is endemic, mosquito bite prevention and participation in mass drug administration programmes are the primary tools for reducing filarial hydrocele risk
  • Prompt evaluation of any new scrotal swelling, which ensures any underlying or coexisting cause is identified early

Common questions

Is a hydrocele dangerous, or could it be cancer?
A hydrocele itself is a benign, non-cancerous condition. The reason proper evaluation, including ultrasound, matters is that a hydrocele can occasionally sit alongside or partly obscure a separate issue — including, in rare cases, a testicular tumour — which is why direct imaging of the testicle, not just examination of the swelling, is a standard part of thorough assessment.
Does a hydrocele need surgery, or can it be left alone?
Not automatically — small, painless hydroceles causing no significant discomfort or cosmetic concern are often simply monitored. Treatment is generally considered when a hydrocele causes meaningful discomfort, has grown significantly, is cosmetically distressing, or when an identified underlying cause needs addressing.
What is the difference between a hydrocele and a varicocele?
They are different conditions affecting different structures. A hydrocele is a fluid collection around the testicle; a varicocele is an enlargement of the veins draining the testicle, feeling more like a "bag of worms" than a smooth fluid-filled swelling. Both can cause scrotal swelling, which is why a proper examination is the reliable way to tell them apart.
What is the difference between a hydrocele and a spermatocele?
A hydrocele involves fluid surrounding the testicle broadly; a spermatocele is a distinct, usually smaller, fluid-filled cyst arising specifically from the epididymis, typically felt as a separate lump above and behind the testicle. Both are generally benign and are often studied together, since they share some overlapping causes and management.
Can a hydrocele affect my fertility?
A simple, uncomplicated hydrocele generally does not directly affect fertility, since it does not typically interfere with normal testicular function or sperm transport. That said, if a hydrocele develops secondary to another condition that does affect fertility — such as significant infection or prior surgery — that underlying cause, rather than the hydrocele itself, is the more relevant consideration.
Why does my hydrocele change size throughout the day?
This pattern is typical of a communicating hydrocele, where an open channel between the abdomen and scrotum allows fluid to shift back and forth depending on position and activity — often larger by the end of the day or after standing, and smaller after lying down. This is a useful clue for your doctor about which type you likely have.
Is it true that hydrocele is a "tropical disease" issue, not relevant to me?
Not entirely — while lymphatic filariasis is the leading global cause and is specifically relevant to men with significant history in endemic regions, hydrocele is also common in non-endemic, higher-income settings, generally from idiopathic, infection-related, injury-related, or post-surgical causes. It is worth mentioning any relevant travel history, but hydrocele is not exclusively a tropical-disease issue.
Can a hydrocele come back after treatment?
Yes, recurrence is a recognised possibility with any approach, though rates vary by method — surgical repair (hydrocelectomy) is generally associated with lower recurrence than aspiration alone, which is part of why sclerotherapy is sometimes used to improve on aspiration-alone results. This is a reasonable question to raise with your specialist regarding your chosen approach.
Is hydrocele aspiration a permanent fix, or does it typically need repeating?
Aspiration alone often provides only temporary relief, with fluid sometimes re-accumulating over time, which is why it is frequently combined with sclerotherapy or reserved for men who are not good surgical candidates, rather than treated as a guaranteed one-time solution. Surgical repair is generally the more definitive option where recurrence after aspiration becomes an issue.
Will hydrocele surgery affect my sex life or how my testicle looks and feels afterward?
Most men recover full normal function and typical appearance after hydrocele surgery, though as with any scrotal surgery, some temporary swelling, bruising, or discomfort during recovery is expected, and specific outcomes are best discussed with your operating surgeon. Complication rates are generally low, though not zero, and it is a reasonable thing to have explained clearly before proceeding.
Can a hydrocele cause pain?
Typically not sharp pain — hydroceles are classically painless or associated with only mild heaviness or dragging discomfort, particularly as they grow larger. Significant or sudden pain associated with scrotal swelling is atypical for a straightforward hydrocele and warrants prompt evaluation to rule out another cause, such as infection or testicular torsion, which is a medical emergency.
Is it normal to have a hydrocele on both sides?
Bilateral hydroceles do occur and are not inherently more concerning than a one-sided hydrocele, though the underlying cause — particularly filariasis in relevant geographic contexts — is sometimes more strongly suggested by bilateral involvement. As with unilateral hydroceles, proper evaluation including ultrasound of both sides remains the standard.
If I had a hydrocele as a baby that was treated, could it come back as an adult?
This is uncommon but possible, and would generally represent a new, separate (acquired, non-communicating) hydrocele rather than a true recurrence of the original congenital type, which is typically definitively resolved by childhood treatment. Any new scrotal swelling in adulthood, regardless of childhood history, deserves its own fresh evaluation.
Does having a large hydrocele mean something more serious is going on?
Not necessarily — hydroceles can grow quite large purely from ongoing fluid accumulation without any more serious underlying cause, particularly idiopathic cases left unaddressed over time. That said, larger hydroceles are more likely to prompt active treatment discussion simply due to the physical discomfort they cause, rather than because size alone signals a more dangerous condition.
Is it worth getting a hydrocele checked even if it does not bother me at all?
Yes, at least once — mainly to confirm what it actually is through proper examination and ultrasound, and to rule out anything else present alongside it, even with no current symptoms. After that initial confirmation, an asymptomatic, uncomplicated hydrocele generally does not need ongoing active treatment, though it is reasonable to keep an eye on changes in size or new symptoms.

Sources

  1. Lundström KJ, et al. Epidemiology of hydrocele and spermatocele; incidence, treatment and complications. Scand J Urol. 2019;53(2-3):134-138. https://pubmed.ncbi.nlm.nih.gov/30990342/
  2. Dagur G, et al. Classifying Hydroceles of the Pelvis and Groin. Curr Urol. 2017;10(1):1-14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5436380/
  3. Current perspectives in the epidemiology and control of lymphatic filariasis. PMC. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12160566/
  4. Shakiba B, et al. Aspiration and sclerotherapy versus hydrocoelectomy. Cochrane Database Syst Rev. 2014;11:CD009735. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD009735.pub2/full
  5. NHS. Hydrocele. https://www.nhs.uk/conditions/hydrocele/