Health condition · Clinically reviewed
Hydrocele, fluid around the testis - when to watch and when to fix.
A soft, painless scrotal swelling that transilluminates. Usually benign, almost always treatable, and worth confirming with a scrotal ultrasound before deciding what to do.
Why trust this guide
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Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
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Sourced from guidance
Checked against BAUS, NICE CKS and peer-reviewed urology sources you can see at the end.
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Current for 2026
Reflects modern UK practice, including scrotal ultrasound as the default work-up and day-case hydrocelectomy.
Key facts
Hydrocele at a glance.
The essentials, in plain English - what it is, the patterns you might have, and how it is worked up and treated in the UK today.
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What it is
A collection of fluid in the tunica vaginalis, the sac that surrounds the testis, producing a soft, painless scrotal swelling.
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Communicating
A paediatric pattern caused by a patent processus vaginalis. The swelling fluctuates through the day and often resolves by one to two years of age.
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Non-communicating
The adult pattern. Primary or idiopathic hydroceles are chronic and gradual. Secondary hydroceles follow trauma, infection or, rarely, a testicular tumour.
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Hydrocele of the cord
Encysted fluid along the spermatic cord above the testis, felt as a separate lump distinct from the testis itself.
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Diagnosis
Clinical - a soft, transilluminable scrotal swelling where the examiner can get above the lump. A scrotal ultrasound confirms and rules out a tumour.
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Treatment
Observation for most children and asymptomatic adults. Aspiration, sclerotherapy or day-case hydrocelectomy (Jaboulay or Lord) when symptoms warrant it.
Why this guide matters
Confirm the diagnosis, then choose the right path.
A scrotal swelling has several possible causes. Getting the diagnosis right, and separating a simple hydrocele from a hernia, an infection or a tumour, is what shapes the next step.
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Ultrasound is the safety net
A scrotal ultrasound confirms the fluid, checks the testis and rules out a tumour before anyone plans treatment.
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Not every hydrocele needs surgery
Most infant communicating hydroceles resolve on their own, and asymptomatic adult hydroceles can be safely watched once causes have been excluded.
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When surgery is chosen, it works
Adult hydrocelectomy is a well-established day-case operation with durable results and low recurrence.
How the diagnosis is made
From first swelling to a clear plan.
The steps a UK GP, urologist or paediatric surgeon will normally follow, in order - so you know what to expect and why.
Phase 1 · Assessing
History, exam and pattern
Phase 2 · Confirming
Scrotal ultrasound and cause
Phase 3 · Planning
Specialist review
- 01
Assessing
Focused history
Onset, size fluctuation, discomfort, any trauma, infection, urinary symptoms or travel to filariasis-endemic areas.
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Assessing
Scrotal examination
A soft, non-tender swelling that transilluminates and where the examiner can get above the mass - a key sign it is not an inguinal hernia.
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Assessing
Distinguish the pattern
Reducibility and daytime fluctuation suggest a communicating hydrocele. A separate lump on the cord points to a hydrocele of the cord.
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Confirming
Scrotal ultrasound
The default UK investigation - confirms fluid around the testis and, crucially, excludes an underlying testicular tumour or other pathology.
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Confirming
Look for a cause
In secondary hydroceles, identify and treat the driver - trauma, epididymitis, orchitis or, rarely, filariasis in travellers.
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Planning
Specialist urology review
Symptomatic, tense or diagnostically uncertain hydroceles are referred to urology for definitive management planning.
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Planning
Paediatric surgical opinion
Persistent communicating hydroceles beyond age one to two, or any hydrocele with hernia features, warrant paediatric urology or surgery input.
Typical timeline: history and scan to a settled plan in a few weeks in most UK pathways.
Symptoms
What a hydrocele actually feels like.
Most hydroceles are painless and soft, with a handful of features that reassure the examiner - and a small set of changes that mean it is time to get seen quickly.
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Painless scrotal swelling
The dominant symptom - a soft, gradually enlarging bulge on one or both sides of the scrotum.
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Fluctuant and soft
Feels like a water-filled balloon rather than a solid lump - fluid gives way under gentle pressure.
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Transilluminates
A light held against the scrotum passes through the fluid - a classic bedside sign of a simple hydrocele.
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Bigger by evening
Communicating hydroceles in children often fill during the day and settle overnight when lying flat.
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Dragging or heaviness
Large or long-standing hydroceles cause a dull, dragging sensation rather than sharp pain.
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You can get above it
On examination, the swelling has a clear upper border in the scrotum - it does not extend into the groin, which helps exclude an inguinal hernia.
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Separate cord lump
A hydrocele of the cord sits above the testis and moves with the cord - distinct from the testis on palpation.
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Red flag - pain, fever or hard lump
Sudden pain, redness, fever or a hard, non-transilluminable mass needs urgent review to exclude torsion, infection or tumour.
Treatment
How a hydrocele is treated in the UK.
Observation for most children and many adults. Aspiration and sclerotherapy in selected patients. Day-case hydrocelectomy when the swelling is symptomatic or bothersome.
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Observation - infants
Most paediatric communicating hydroceles resolve by one to two years as the processus vaginalis closes. Watchful waiting is the default.
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Observation - asymptomatic adults
Small, painless, stable hydroceles in adults can safely be monitored once a tumour has been excluded on ultrasound.
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Needle aspiration
Drainage of fluid gives quick relief but almost always recurs. Useful for frail patients or as a temporising step before surgery.
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Aspiration and sclerotherapy
Aspiration followed by an agent such as tetracycline, doxycycline or polidocanol. A specialist alternative to surgery in selected adults.
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Paediatric surgery
Laparoscopic or open ligation of the patent processus vaginalis by a paediatric urologist or surgeon - the definitive fix for persistent communicating hydroceles.
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Jaboulay procedure
Adult hydrocelectomy by eversion of the sac - a well-established day-case operation performed by urology.
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Lord procedure
Adult hydrocelectomy by plication of the sac - suited to thin-walled hydroceles, with less dissection and low recurrence.
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Treat the underlying cause
For secondary hydroceles, treat the driver - antibiotics for epididymo-orchitis, urgent review for suspected tumour, or filaricide in confirmed filariasis.
What this guide is based on
The sources behind every claim on this page.
UK national guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your GP or urologist knows your history and examination and can tell you which parts apply to you. If in doubt, get seen.
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British Association of Urological Surgeons (BAUS). Patient information on hydrocele and hydrocelectomy.
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NICE Clinical Knowledge Summaries. Scrotal pain and swelling.
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European Association of Urology (EAU). Guidelines on paediatric urology - communicating hydrocele.
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Royal College of Surgeons of England. Commissioning guide for scrotal conditions.
Red flags
When a scrotal swelling needs urgent attention.
Most hydroceles are benign and unhurried. These are the features that change that - and where a same-day or urgent opinion is needed.
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Sudden severe scrotal pain
Not typical of a simple hydrocele - urgent review to exclude testicular torsion, which is a surgical emergency.
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Fever and tender scrotum
Suggests epididymo-orchitis rather than an uncomplicated hydrocele - needs prompt antibiotics and reassessment.
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Hard, non-transilluminable mass
A solid component or failure to transilluminate raises concern for a testicular tumour - urgent ultrasound and urology referral.
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Rapidly enlarging swelling
A hydrocele that expands quickly, especially after minor trauma, may be a haematocele and needs urgent assessment.
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Tense, painful hydrocele
A hydrocele under high pressure can be very uncomfortable and, rarely, compromise the testis - warrants earlier surgical review.
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Signs of skin infection
Redness, warmth or discharge over the scrotum suggests cellulitis or an infected hydrocele - needs assessment for antibiotics or drainage.
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Groin extension of the swelling
If the swelling extends into the inguinal canal or the examiner cannot get above it, an inguinal hernia must be considered.
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New hydrocele in a young adult
Unexplained hydrocele in a man aged 15 to 45 warrants scrotal ultrasound to exclude an underlying testicular tumour.
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Travel to filariasis-endemic areas
A hydrocele in someone returning from tropical regions may reflect lymphatic filariasis - needs specialist infection and urology input.
Living with it
A benign problem, with a clear ladder.
Four things that make the biggest difference day to day - honest reassurance, comfortable support, knowing which changes matter, and choosing surgery when it is the right time.
A quiet reminder
A confirmed diagnosis is worth more than a quick fix.
A short work-up with a scrotal ultrasound is quick, painless and gives you and your clinician the confidence to choose the right path.
- 01 Reassurance
Most hydroceles are benign
Once a tumour and hernia are excluded, a simple hydrocele is not dangerous. It is a comfort and cosmetic decision, not a cancer risk.
- 02 Comfort
Supportive underwear helps
Well-fitting supportive briefs reduce the dragging sensation of larger hydroceles, especially during activity or long days on your feet.
- 03 Watch
Know what to look out for
Sudden pain, rapid growth, redness or a hard lump changes the picture - see a clinician promptly if any of these appear.
- 04 Escalate
Surgery is a good option when ready
If the hydrocele is bothering you, day-case hydrocelectomy is well established, low risk and produces durable results.
Frequently asked
Everything we get asked about hydrocele.
Quick answers on diagnosis, how it differs from a hernia, when surgery is needed and what to expect afterwards.
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What is a hydrocele?
A hydrocele is a collection of fluid within the tunica vaginalis, the thin sac that surrounds the testis. It produces a soft, usually painless scrotal swelling. In children it is often communicating - linked to a patent processus vaginalis - and in adults it is usually non-communicating, either primary or secondary to trauma, infection or, rarely, a testicular tumour.
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How is a hydrocele diagnosed?
The diagnosis is clinical - a soft, fluctuant scrotal swelling that transilluminates and where the examiner can get above the mass, which helps distinguish it from an inguinal hernia. A scrotal ultrasound is the standard investigation in the UK to confirm the fluid, assess the testis and exclude an underlying testicular tumour.
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Does a hydrocele always need surgery?
No. Most infant communicating hydroceles resolve on their own by one to two years of age. Small, painless, stable hydroceles in adults can be monitored once serious causes have been excluded. Surgery is offered when the hydrocele is symptomatic, enlarging, cosmetically troublesome or diagnostically uncertain.
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What is the difference between a hydrocele and a hernia?
A hydrocele is fluid confined to the scrotum, so the examiner can get above the swelling and it usually transilluminates. An inguinal hernia contains bowel or fat that has passed through the inguinal canal, so it extends up into the groin, does not transilluminate and may be tender, with impulse on coughing.
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What does hydrocele surgery involve?
In adults, hydrocelectomy is typically a day-case operation under general or spinal anaesthesia. The Jaboulay procedure everts the sac around the testis, and the Lord procedure plicates a thin-walled sac. In children, the patent processus vaginalis is ligated, usually laparoscopically or through a small groin incision by a paediatric urologist.
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What happens if a hydrocele is left untreated?
Many hydroceles cause no harm and can safely be left alone. Large or long-standing hydroceles may become uncomfortable or unsightly, and rare complications include infection, haematocele after minor trauma and, very occasionally, effects on testicular comfort. Any change in the character of a hydrocele - sudden pain, rapid growth or a hard lump - should be reviewed promptly.
Related content
Keep reading.
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Inguinal hernia
A key differential for scrotal swelling.
Learn more -
Testicular torsion
Sudden severe pain - a surgical emergency.
Learn more -
Epididymitis
Inflammation of the epididymis and scrotum.
Learn more -
Orchitis
Testicular inflammation, often infective.
Learn more -
Erectile dysfunction
A related men’s health topic.
Learn more -
Hydrocelectomy
Day-case surgery to remove a hydrocele.
Learn more -
Testicular ultrasound
The default scan for scrotal swellings.
Learn more -
Private ultrasound scan
Rapid diagnostic imaging in a private setting.
Learn more