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# Hydrocele

A hydrocele is a build-up of fluid in the sac around a testis, causing a painless swelling of the [scrotum](https://durgical.com/en/anatomy/scrotum/); it is common in newborns and also occurs in men.

Updated 2026-10-29

## Structures involved

Tap one to see what it is and open it in 3D.

- [Testes](https://durgical.com/en/anatomy/testis/)
- [Scrotum](https://durgical.com/en/anatomy/scrotum/)
- [Spermatic cord](https://durgical.com/en/anatomy/spermatic-cord/)
- [Epididymis](https://durgical.com/en/anatomy/epididymis/)
- [Ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/)

## Microorganisms that cause it

- [Wuchereria bancrofti / Brugia malayi](https://durgical.com/en/microbiology/wuchereria-bancrofti-brugia-malayi/)

## In embryology

- [Gonads and the descent of the testis](https://durgical.com/en/embryology/gonads-and-the-descent-of-the-testis/)
- [Processus vaginalis: hydrocele and indirect inguinal hernia](https://durgical.com/en/embryology/processus-vaginalis-hydrocele-and-indirect-inguinal-hernia/)

## In the clinical exam

- [Male genital exam: transillumination, cremasteric reflex, Prehn sign](https://durgical.com/en/clinical-exam/male-genital-exam-transillumination-cremasteric-reflex-prehn-sign/)

## Why it happens

- [Edema and effusions: the four mechanisms](https://durgical.com/en/general-pathology/edema-and-effusions-the-four-mechanisms/)
- [Serous membranes: pleura and peritoneum](https://durgical.com/en/histology/serous-membranes-pleura-and-peritoneum/)

## What it is

A collection of fluid between the layers of the tunica vaginalis around the testis, causing a painless scrotal swelling. It is common in newborns and also appears in adult men.

## Who gets it

It is frequent in newborn boys, especially preterm infants, and most congenital hydroceles resolve during the first one to two years. In adults it is usually acquired. Filariasis causes hydroceles in endemic tropical areas.

## Causes

- Congenital: a patent processus vaginalis lets peritoneal fluid reach the scrotum
- Idiopathic adult hydrocele: imbalance between fluid secretion and absorption by the tunica vaginalis
- Secondary to epididymitis or orchitis
- Secondary to testicular torsion, trauma or testicular tumour
- After inguinal surgery, such as varicocele or hernia repair
- Lymphatic filariasis in endemic regions

## Risk factors

- Prematurity
- Patent processus vaginalis (also linked to inguinal hernia)
- Scrotal trauma or infection
- Previous inguinal or scrotal surgery
- Residence in areas endemic for filariasis

## Pathophysiology

The tunica vaginalis normally holds a thin film of fluid. In communicating hydroceles, peritoneal fluid flows through an open processus vaginalis, so the size changes during the day; in non-communicating ones, the fluid is trapped because production exceeds absorption or lymphatic drainage is impaired.

## Classification

- Communicating (open processus vaginalis) or non-communicating
- Congenital or acquired (primary or secondary)
- Hydrocele of the [spermatic cord](https://durgical.com/en/anatomy/spermatic-cord/) (encysted fluid along the cord)

## Symptoms and signs

- Painless, smooth swelling of one or both sides of the scrotum
- Feeling of heaviness or discomfort when large
- Swelling that grows during the day and shrinks overnight in communicating hydroceles
- The testis may be hard to feel within the fluid

## Red flags

- Sudden scrotal pain (torsion, epididymitis)
- A hard or irregular testis, or a testis that cannot be felt (rule out tumour by ultrasound)
- Swelling that cannot be reduced, with pain or vomiting (incarcerated hernia)
- New hydrocele in a young adult without a clear cause

## Diagnosis

**Clinical**
Smooth, fluctuant swelling that transilluminates, with the examiner able to get above it (unlike an inguinoscrotal hernia). Changes in size suggest a communicating hydrocele.

**Tests**
Usually none. Tumour markers are measured if ultrasound shows a testicular mass.

**Imaging**
Scrotal ultrasound confirms fluid around the [testis](https://durgical.com/en/anatomy/testis/) and checks the testis itself, especially when it cannot be palpated or the cause is unclear.

## Differential diagnosis

- Inguinal hernia
- Spermatocele or epididymal cyst
- Testicular tumour
- Varicocele
- Epididymitis or orchitis
- Haematocele after trauma

## Goal of treatment

Confirm the testis is normal, relieve symptoms and, in communicating hydroceles, close the patent processus vaginalis to prevent a hernia.

## Treatment

**Follow-up**
Observation for most congenital hydroceles, which often resolve within the first one to two years; small, painless adult hydroceles may also be observed.

**Surgical**
Children: ligation of the patent processus vaginalis through an inguinal incision. Adults: scrotal hydrocelectomy (excision or plication of the tunica vaginalis).

**Procedure**
Aspiration with sclerotherapy for selected adults who are poor surgical candidates; recurrence is more common than after surgery.

**Medical**
Treatment of the cause in secondary hydroceles, such as antibiotics for epididymitis or antiparasitic therapy for filariasis.

## Complications

- Discomfort and difficulty walking or with clothing when very large
- Inguinal hernia in communicating hydroceles
- After surgery: haematoma, infection, recurrence and, rarely, injury to the [epididymis](https://durgical.com/en/anatomy/epididymis/) or [ductus deferens](https://durgical.com/en/anatomy/ductus-deferens/)

## Prognosis

Excellent. Most infant hydroceles resolve on their own, and surgery in adults has a low recurrence rate. The outlook of secondary hydroceles depends on the cause.

## Test yourself

Think of the answer, then tap the question to see it.

## What embryological structure stays open in a communicating hydrocele?

The processus vaginalis, which lets peritoneal fluid reach the scrotum.

## Which bedside sign helps distinguish a hydrocele from a solid testicular mass?

Transillumination: a hydrocele lets light through, a solid mass does not.

## How is a hydrocele distinguished from an inguinoscrotal hernia on examination?

The examiner can get above a hydrocele, but not above a hernia that extends from the inguinal canal.

## Why is ultrasound important in a new hydrocele in a young adult?

It confirms the testis is normal, since a testicular tumour can present with a secondary hydrocele.

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## Related conditions

- [Inguinal hernia](https://durgical.com/en/conditions/inguinal-hernia/)
- [Testicular torsion](https://durgical.com/en/conditions/testicular-torsion/)
- [Epididymitis](https://durgical.com/en/conditions/epididymitis/)
- [Varicocele](https://durgical.com/en/conditions/varicocele/)
- [Testicular cancer](https://durgical.com/en/conditions/testicular-cancer/)
- [Cryptorchidism (undescended testis)](https://durgical.com/en/conditions/cryptorchidism/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Hydrocele](https://www.ncbi.nlm.nih.gov/books/NBK559125/) (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/hydrocele/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/hydrocele/