Hydrocele

Definition

A hydrocele is a fluid collection that resides within the tunica vaginalis in the scrotum, or within the processus vaginalis in the inguinal canal. It is the most common cause of painless scrotal swelling in children.

Anatomy & Embryology

As the testis descends into the scrotum, the peritoneal extension alongside it (the processus vaginalis) forms a serous covering called the tunica vaginalis. Normally, the processus vaginalis obliterates after descent. Failure of obliteration leads to various anatomic conditions:

Anatomic variations with different degrees of processus vaginalis obliteration

A: Normal (obliterated); B: Proximal hernia sac, distal obliterated; C: Complete hernia into scrotum; D: Hydrocele of the cord (proximal + distal obliteration, mid-segment open); E: Non-communicating scrotal hydrocele; F: Patent processus with communicating hydrocele (Mulholland & Greenfield's Surgery, 7e)

The incidence of patent processus vaginalis is 80–94% in newborns, declining to 20–30% in adulthood.

Classification

Type	Key Feature	Natural History
Non-communicating	Processus vaginalis closed; isolated residual fluid	Usually resolves by 12–18 months
Communicating	Patent processus vaginalis — fluid fluctuates with activity/posture	Does not resolve; synonymous with patent processus vaginalis
Hydrocele of the cord	Fluid in the processus vaginalis separate from tunica vaginalis	Does not resolve spontaneously
Hydrocele of canal of Nuck	Female equivalent; fluid trapped in processus vaginalis	—
Abdominoscrotal hydrocele	Rare (~1.25% of all hydroceles); tense, extends into abdomen; bilateral in ~30%	May manifest in infancy; can enlarge, improve, or rarely resolve spontaneously

Etiology

Congenital/Primary:

Patent processus vaginalis (children)

Secondary (acquired) causes:

Trauma
Epididymo-orchitis / infection
Testicular/paratesticular tumors
Lymphatic obstruction (e.g., post-varicocelectomy — incidence 3–33%, avg ~7%)
Torsion of appendix testis
Incarcerated inguinal hernia (acute hydrocele)

Clinical Features

Painless scrotal swelling (hallmark)
May be intermittent — resolves when supine, enlarges when upright or with Valsalva (communicating type)
Soft, fluctuant mass; testis not separately palpable
Transillumination positive — the fluid-filled sac illuminates brightly with a light source; contrast with solid masses or testicular enlargement which do not transilluminate

Diagnosis

Clinical: History + transillumination is usually sufficient.

Scrotal ultrasound (when needed):

Confirms fluid collection (anechoic area surrounding testis)
Identifies unpalpable testis surrounded by hydrocele fluid
Differentiates simple from complex hydrocele (debris, septations = secondary cause)
Rules out testicular malignancy

Scrotal ultrasound showing large simple hydrocele — anechoic fluid surrounding the ovoid testis

B-mode ultrasound: large anechoic fluid collection surrounding the testis — classic simple hydrocele.

Management

Infants & Children

Non-communicating hydrocele: Observe until age 12 months — most resolve spontaneously
Indications for surgery:
- Persists beyond age 1 year
- Enlargement or size fluctuation (implies communication developing)
- Communicating hydrocele (treat as patent processus vaginalis)
- Hydrocele of the spermatic cord (rarely resolves spontaneously)
Acute hydrocele from incarcerated hernia → urgent surgical exploration

Surgical Techniques

Children (communicating hydrocele): Inguinal approach — high ligation of the hernia sac at the internal inguinal ring; hydrocele sac excised
Peripubertal/adults (non-communicating): Trans-scrotal hydrocele repair; inguinal approach only if communicating
Laparoscopic approach: Increasingly used, particularly for bilateral cases; some centers report single-port techniques

Adults (primary/secondary hydrocele)

Option	Notes
Observation	Asymptomatic small hydroceles
Aspiration ± sclerotherapy (AS)	Resolution rate 85–96%; repeat procedures may be needed
Hydrocelectomy	Definitive; recurrence rate 0–2% regardless of technique

Recurrence & Complications

Surgical recurrence: 0–2% (any operative technique)
Sclerotherapy resolution: 85–96%
Post-varicocelectomy hydrocele: 3–33% (avg 7%) — due to lymphatic obstruction; use of microsurgical technique almost eliminates this risk
Large hydrocele creates an insulating layer around the testis → may impair counter-current heat exchange → potentially affects fertility after varicocelectomy

Special Considerations

Abdominoscrotal hydrocele: Tense, non-communicating scrotal mass extending retroperitoneally/preperitoneally. Ultrasound defines proximal extent. Associated with cryptorchidism, contralateral hernia/hydrocele, and vanishing testis.

Emergency differentiation: Acute non-communicating hydrocele must be differentiated from incarcerated inguinal hernia and inguinal lymphadenitis — transillumination and palpation of normal cord structures above the mass help distinguish.

Sources: Campbell-Walsh-Wein Urology; Mulholland & Greenfield's Surgery, 7e; Tintinalli's Emergency Medicine

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