Hydrocele

1. Overview

A hydrocele is an abnormal collection of serous fluid within the potential space created by the tunica vaginalis — the double-layered peritoneal remnant that envelops the testis and epididymis. It is the most common cause of painless scrotal swelling in men and boys, ranging from benign congenital fluid collections in newborns that resolve on their own to secondary presentations in adults that may signal an underlying condition requiring urgent investigation.

In newborns, hydroceles are present in roughly 1–2% of full-term male infants at birth and represent the residual of incomplete obliteration of the processus vaginalis after testicular descent. The vast majority — around 80% — close spontaneously within the first 12 to 18 months of life as the peritoneal connection seals off naturally. Those that persist beyond 18 months, or that fluctuate noticeably in size from day to day (a hallmark of communication with the peritoneal cavity), generally require surgical repair.

In adult men, a new or enlarging hydrocele can be more than a nuisance. Secondary hydroceles can develop in response to testicular torsion, epididymo-orchitis, trauma, or — critically — a testicular tumor. Ultrasound is the test that separates a simple hydrocele from a testicular tumor, and it is the standard test for any adult with a newly discovered scrotal fluid collection.

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2. Anatomy and Pathophysiology

To understand hydrocele formation, a brief excursion into embryology is essential. As the testis descends from the retroperitoneum into the scrotum during fetal development (typically between the seventh and ninth month of gestation), it carries a fingerlike protrusion of peritoneum with it — the processus vaginalis. This peritoneal sleeve forms a conduit connecting the abdominal cavity to the scrotum.

Under normal circumstances, the proximal portion of the processus vaginalis obliterates after testicular descent is complete, leaving only the distal portion intact as the tunica vaginalis — a closed serous cavity with a visceral layer tightly adherent to the testis and epididymis, and a parietal layer lining the inner scrotal wall. The normal tunica vaginalis contains 1–3 mL of serous fluid that lubricates the testis and allows it to move freely within the scrotum.

Hydrocele develops when this fluid balance is disrupted:

• Failure of obliteration — the processus vaginalis remains patent, allowing peritoneal fluid to communicate freely with the tunica vaginalis (communicating hydrocele).
• Imbalance of secretion and absorption — the mesothelial lining of the tunica vaginalis secretes more fluid than the lymphatics can drain, accumulating within a closed sac (noncommunicating hydrocele).
• Reactive exudation — inflammation, trauma, or tumor disrupts the normal secretion–absorption balance, triggering a secondary hydrocele.

The fluid itself is typically clear, straw-colored, and protein-rich. In pyocele (infected hydrocele) it becomes purulent; in hematocele (blood-filled after trauma) it is sanguineous.

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3. Types and Classification

Hydroceles are classified by the anatomical relationship between the fluid sac and the peritoneal cavity, and by whether a primary or secondary cause is identified.

Communicating Hydrocele

Caused by a patent processus vaginalis — the peritoneal connection to the scrotum has not closed. Peritoneal fluid flows freely into and out of the tunica vaginalis depending on intra-abdominal pressure and body position. Key features include:

• Size varies throughout the day — typically larger in the evening (upright posture, increased intra-abdominal pressure) and smaller after a night of lying flat.
• May be compressible — gentle pressure can reduce the fluid back into the abdomen.
• Functionally equivalent to an indirect inguinal hernia: the same patent pathway through the internal inguinal ring is present. If bowel or omentum descends through that same patent processus, the diagnosis becomes a hernia. Distinguishing the two preoperatively can be challenging [ Search PubMed].
• Represents the predominant type in infants.

Noncommunicating (Simple) Hydrocele

The processus vaginalis has closed, but fluid has accumulated — or failed to reabsorb — within the isolated tunica vaginalis sac. Key features include:

• Size is stable throughout the day; does not fluctuate with activity or position.
• Cannot be reduced manually.
• May be congenital (processus closed but residual fluid did not resorb) or acquired (reactive to minor trauma or inflammation that resolved).

Secondary Hydrocele

Develops as a consequence of another scrotal pathology. Common underlying causes include:

• Infection — epididymo-orchitis (bacterial or viral) is the leading cause of secondary hydrocele in adults.
• Testicular torsion — reactive fluid accumulates rapidly alongside venous congestion and ischemia.
• Trauma — blunt scrotal injury triggers an exudative response; a concurrent hematocele may be present.
• Testicular tumor — 10–15% of testicular germ cell tumors present with an associated hydrocele. This is the most important diagnosis to exclude in adults.
• Filariasis (tropical regions) — Wuchereria bancrofti obstructs lymphatic drainage, producing large bilateral hydroceles alongside lymphedema.

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4. Epidemiology

Hydrocele is the most common cause of scrotal swelling in newborns, with a reported prevalence of 1–2% among full-term male infants. Premature infants have a substantially higher rate, reflecting less complete obliteration of the processus vaginalis at the time of birth.

Key epidemiological points:

• Spontaneous resolution occurs in approximately 80% of congenital hydroceles by 12–18 months of age as the processus vaginalis naturally seals.
• Hydroceles persisting beyond 18–24 months are very unlikely to resolve without intervention and warrant surgical consultation.
• In adults, hydrocele has a bimodal distribution: a smaller peak in young adult men (often secondary to epididymo-orchitis) and a larger peak in men over 40 (often idiopathic or related to minor repeated microtrauma) [ Search PubMed].
• Worldwide, Wuchereria bancrofti filariasis is the leading cause of hydrocele in tropical regions, responsible for millions of cases across sub-Saharan Africa and Southeast Asia.
• Hydrocele represents 1–5% of all hernia and scrotal operations performed in general surgical and urological practice in developed countries.

Because the processus vaginalis follows the same anatomical course as an indirect inguinal hernia, a communicating hydrocele is considered a hernia-spectrum condition. Surgeons repair both through the inguinal approach in children, and the inguinal exploration often reveals a patent internal ring even when hernia contents were not clinically apparent preoperatively.

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5. Clinical Presentation and Diagnosis

The classic presentation of a primary hydrocele is a smooth, soft, nontender, translucent scrotal swelling that the examiner can get above (i.e., the upper border is palpable separately from the inguinal canal contents). This distinguishes it from an inguinoscrotal hernia, where the swelling extends through the external inguinal ring and one cannot palpate a distinct upper border.

Transillumination

The most important bedside test is transillumination: in a darkened room, a bright penlight or flashlight placed firmly against the posterior scrotum will transmit light through the fluid-filled sac, causing the scrotum to glow red. A solid mass — tumor, organized hematocele, or pyocele — blocks light transmission. While transillumination is highly suggestive of hydrocele, it is not definitive; some cystic testicular tumors can also transilluminate, and thick-walled or infected hydroceles may not. Ultrasound is always required to confirm [ Search PubMed].

Scrotal Ultrasound

High-resolution scrotal ultrasound (7.5–15 MHz linear probe) is the definitive imaging modality. It reliably:

• Confirms the fluid collection and distinguishes it from a solid mass.
• Characterizes the fluid as simple (anechoic, no internal echoes — consistent with uncomplicated hydrocele) or complex (echogenic debris or septations — suggests pyocele, hematocele, or tumor).
• Evaluates the underlying testis for parenchymal lesions, masses, or microlithiasis.
• Assesses testicular blood flow with color Doppler (reduced flow in torsion; increased flow in epididymo-orchitis).

In an adult man with a newly discovered hydrocele, scrotal ultrasound is the test that rules out a hidden (occult) testicular tumor. Up to 10–15% of testicular germ cell tumors are discovered incidentally when the clinician orders ultrasound for a hydrocele. Tumor markers (AFP, beta-hCG, lactate dehydrogenase, LDH) are also checked when ultrasound findings are ambiguous.

History Clues

• Variation with posture or time of day — suggests communicating hydrocele (patent processus vaginalis).
• Rapid onset with pain and fever — suggests secondary hydrocele from epididymo-orchitis or torsion (emergency).
• Recent trauma — raises concern for hematocele.
• Travel to tropics — consider filariasis; check for lower-limb lymphedema.

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6. Treatment

Treatment decisions are guided by the patient's age, hydrocele type, symptoms, and any identified underlying cause.

Congenital Hydrocele in Infants and Young Children

Watchful waiting is the first-line approach for infants under 12–18 months. With 80% spontaneous resolution expected, immediate surgery is not usually done. Parents are usually reassured; the signs that bring a child back are a hydrocele that enlarges, signs of incarcerated hernia (acute onset pain, irreducibility, vomiting), or swelling that has not resolved by 18 months [ PubMed PMID: 9728185].

When surgery is indicated (no resolution by 18–24 months, communicating hydrocele, symptomatic enlargement), the standard operation is hydrocelectomy via an inguinal approach:

• The inguinal incision allows identification and high ligation of the patent processus vaginalis at the level of the internal inguinal ring.
• Any associated hernia can be repaired simultaneously through the same incision.
• The distal sac is opened and left open (rather than excised), which avoids injury to the vas deferens and testicular vessels.
• Day-case (ambulatory) procedure under general anaesthesia; recovery is typically 1–2 weeks.

A keyhole (laparoscopic) option also exists for children. In a 2024 review of 198 children operated on for communicating hydrocele between 2019 and 2024, 87 had laparoscopic percutaneous internal ring suturing (PIRS), in which the open channel is stitched closed at the internal ring under camera guidance, and 111 had open ligation. Neither group had a single recurrence. Complications after surgery occurred in 2.3% after PIRS and 6.3% after open surgery, a difference that was not statistically significant. The median operation took 15 minutes with PIRS against 21 minutes open, and the median hospital stay was 9 hours against 24 hours [ PubMed PMID: 38671654].

Adult Hydrocele — Surgical Repair

In adults, the preferred operation is hydrocelectomy via a scrotal approach:

• Jaboulay procedure (eversion): the hydrocele sac is opened, everted, and sutured behind the testis, creating a raw surface that prevents re-accumulation. Most widely performed.
• Lord's procedure: the sac is plicated (gathered into radial folds with absorbable sutures) rather than excised — preferred for smaller, thinner-walled hydroceles. Lord described it in 1964 as a bloodless operation [ Search PubMed]; in a 2001 comparison of techniques (below), postoperative scrotal swelling (oedema) was most common after plication, at 74%.
• Excision of the entire sac: reserved for very large, thick-walled hydroceles where eversion is impractical; higher risk of hematoma.

The 2001 comparison followed 132 men (mean age 54) whose idiopathic hydrocele was repaired between 1990 and 1998 by excision, eversion/plication or internal drainage. Excision had the most complications (81%) and internal drainage the fewest (7%), while internal drainage had the most recurrences (85%) and excision the fewest (1.3%). Wound infection and haematoma rates did not differ significantly between the three. The authors suggested giving up internal drainage and judged plication better than excision because it caused fewer complications [ PubMed PMID: 11121997].

Aspiration and Sclerotherapy

Simple needle aspiration drains the hydrocele fluid but has a recurrence rate exceeding 70% within 12 months, because the secreting tunica vaginalis lining remains intact. For this reason it is not used as a definitive treatment except when surgery carries prohibitive risk.

Sclerotherapy (aspiration followed by instillation of a sclerosing agent such as tetracycline, polidocanol, or phenol) destroys the mesothelial lining and reduces recurrence to 30–50% — still higher than surgery but acceptable for elderly men or those unfit for general anaesthesia. Complications include pain, infection, and inadvertent injury to adjacent structures. Ultrasound to exclude an underlying tumor comes before sclerotherapy.

Secondary Hydrocele

The underlying cause is treated first:

• Epididymo-orchitis: antibiotics (empirical fluoroquinolone or doxycycline/ceftriaxone depending on likely pathogen); most reactive hydroceles resolve as the infection clears.
• Testicular torsion: emergency surgical detorsion within 6 hours (orchiopexy bilaterally); any resulting reactive hydrocele is addressed once the acute situation is resolved.
• Testicular tumor: radical inguinal orchidectomy (the hydrocele is part of the orchiectomy specimen); scrotal incision is absolutely contraindicated as it disrupts lymphatic drainage planes and upstages the tumor.
• Filariasis: diethylcarbamazine (DEC) or ivermectin-based antiparasitic therapy; large hydroceles may still require surgical correction once the parasitic load is controlled. In a double-blind, placebo-controlled trial in Ghana (2009), 42 men with filarial hydrocele took either doxycycline 200 mg a day for six weeks or a placebo. Doxycycline is a widely available generic antibiotic; here it targets Wolbachia, bacteria that live inside the Wuchereria bancrofti worm. Compared with placebo it lowered Wolbachia levels, the worm larvae in the blood (microfilariae) and worm antigen, and in men with active infection it lowered the blood growth factor VEGF-A, a fall that came before a reduction in hydrocele stage. Four months after doxycycline, all the men received ivermectin and albendazole, the drugs used in that area's mass treatment campaigns [ PubMed PMID: 19478258].

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7. Complications

Primary hydroceles are benign and their main complications are related to either the natural history of the disease or to treatment:

Complications of Untreated Hydrocele

• Pyocele — bacterial infection of the hydrocele fluid, presenting with acute scrotal pain, fever, and erythema. Requires urgent surgical drainage and antibiotics. Can progress to Fournier's gangrene in immunocompromised patients.
• Hematocele — bleeding into the hydrocele sac, most commonly after trauma or anticoagulation. The scrotum becomes acutely tender and firm; ultrasound shows echogenic fluid. Large hematoceles require surgical evacuation.
• Pressure effects — a very large chronic hydrocele may cause discomfort, difficulty with ambulation, or scrotal skin excoriation from gravitational drag, although this is uncommon.
• Missed underlying pathology — the most serious "complication" of a missed secondary hydrocele is a delayed diagnosis of testicular cancer [ Search PubMed].

Surgical Complications

• Hematoma — the most common postoperative complication, occurring in 1–5% of cases; most resolve spontaneously, but large hematomas may require evacuation.
• Wound infection — uncommon (~1%); treated with antibiotics and wound care.
• Recurrence — approximately 1–5% after formal hydrocelectomy; higher after aspiration (up to 70%) or sclerotherapy (30–50%).
• Injury to the vas deferens or testicular vessels — rare but potentially serious; may cause testicular atrophy or subfertility if both the testicular artery and the deferential artery are compromised.
• Chronic scrotal pain — a small proportion of patients report persistent discomfort after hydrocelectomy, likely from nerve entrapment or scar tissue formation.

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8. Differential Diagnosis

Several conditions can mimic a hydrocele. Accurate differentiation relies on history, physical examination, and ultrasound.

• Inguinoscrotal hernia — extends into the inguinal canal; examiner cannot get above the mass; bowel sounds may be heard on auscultation; does not transilluminate (unless contains fluid-filled loop); may be reducible.
• Varicocele — "bag of worms" texture on palpation; predominantly left-sided (90%); increases with Valsalva maneuver; pain is typically described as a dull ache worsening during the day; confirmed with Doppler ultrasound showing venous reflux.
• Epididymal cyst / Spermatocele — cystic swelling arising from the epididymis (posterior-superior testis); distinct from and palpable separately from the testis; transilluminates; spermatocele contains milky fluid with spermatozoa; ultrasound differentiates from hydrocele by location.
• Testicular tumor — hard, non-tender, does not transilluminate; cannot be separated from the testis on palpation; associated hydrocele may be present; AFP/beta-hCG may be elevated; urgent ultrasound + tumor markers are the standard work-up.
• Epididymo-orchitis — tender swelling with fever, scrotal erythema, and warmth; secondary reactive hydrocele may coexist; Doppler shows increased testicular blood flow.
• Testicular torsion — acute onset severe pain; high-riding testis with horizontal lie; absent cremasteric reflex; emergency Doppler shows absent or markedly reduced testicular flow; surgical exploration is not delayed for imaging.
• Hematocele — firm, heavy, non-transilluminating scrotal mass after trauma or in a patient on anticoagulants; history and ultrasound (echogenic fluid with dependent debris) are diagnostic.

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Key Research Papers

The following landmark studies have shaped current understanding and management of hydrocele:

Watchful Waiting and Timing of Surgery in Infants

Kapur et al. (1998) reviewed hernias and hydroceles in infants and children — their embryology, incidence, clinical presentation and treatment, with special emphasis on when a child is referred to a pediatric surgeon [ PubMed PMID: 9728185]. Communicating hydroceles are repaired by inguinal exploration and high ligation of the processus vaginalis, which closes the hernia pathway.

Lord's Plication Procedure

Lord's original description of the plication procedure (bloodless operation for idiopathic hydrocele) remains a milestone in hydrocele surgery, offering reduced hematoma risk and quicker recovery compared to sac excision — particularly relevant for smaller hydroceles in older patients [ Search PubMed].

Three Adult Surgical Techniques Compared

Ku et al. (2001) compared excision, eversion/plication and internal drainage in 132 men with idiopathic hydrocele. Excision had the highest complication rate (81%) and the lowest recurrence (1.3%); plication had the most postoperative scrotal swelling (74%); internal drainage had the highest recurrence (85%), and the authors suggested abandoning it [ PubMed PMID: 11121997].

Adult Hydrocele Management Review

Rioja et al. provided a comprehensive review of adult hydrocele management, comparing surgical repair (hydrocelectomy) with aspiration-sclerotherapy and concluding that surgical repair offers the lowest recurrence rates and should be the default approach for symptomatic adults who are operative candidates [ Search PubMed].

Scrotal Emergencies in Children

Baldisserotto reviewed the imaging characteristics of pediatric scrotal emergencies including hydrocele variants, emphasizing the ultrasound features that distinguish simple hydrocele from urgent pathology such as torsion, incarcerated hernia, and pyocele [ Search PubMed].

Ultrasound Before Groin Surgery in Children

Erez et al. (2002) compared ultrasound measurements of the groin taken before surgery with what surgeons found at operation in 642 children (1,284 groins). The average groin width was 3.6 mm when the canal was normal, 4.9 mm with an open processus vaginalis, 4.8 mm with a hydrocele, 7.2 mm with a full hernia and 12.8 mm with a large hernia. The study gives ultrasound criteria for planning groin surgery; it does not report long-term outcomes [ PubMed PMID: 12037751].

Further reading: PubMed: hydrocele management pediatric PubMed: hydrocele surgery outcomes PubMed: hydrocele sclerotherapy aspiration

1. Kapur P, Caty MG, Glick PL. "Pediatric hernias and hydroceles." Pediatr Clin North Am. 1998;45(4):773–789. — PubMed PMID: 9728185
2. Erez I, Rathause V, Vacian I, et al. "Preoperative ultrasound and intraoperative findings of inguinal hernias in children: a prospective study of 642 children." J Pediatr Surg. 2002;37(6):865–868. — PubMed PMID: 12037751
3. Rioja J, Sánchez-Margallo FM, Usón J, Rioja LA. "Adult hydrocele and spermatocele." BJU Int. 2011;107(11):1852–1864. — Search PubMed
4. Baldisserotto M. "Scrotal emergencies." Pediatr Radiol. 2009;39(5):516–521. — PubMed PMID: 19189096
5. Lord PH. "A bloodless operation for the radical cure of idiopathic hydrocele." Br J Surg. 1964;51:914–916. — PubMed PMID: 14226052
6. Ku JH, Kim ME, Lee NK, Park YH. "The excisional, plication and internal drainage techniques: a comparison of the results for idiopathic hydrocele." BJU Int. 2001;87(1):82–84. — PubMed PMID: 11121997
7. Debrah AY, Mand S, Marfo-Debrekyei Y, et al. "Reduction in levels of plasma vascular endothelial growth factor-A and improvement in hydrocele patients by targeting endosymbiotic Wolbachia sp. in Wuchereria bancrofti with doxycycline." Am J Trop Med Hyg. 2009;80(6):956–963. — PubMed PMID: 19478258
8. Pogorelić Z, Stanić P, Bašković M. "Comparison of Percutaneous Internal Ring Suturing (PIRS) versus Open Ligation of the Patent Processus Vaginalis for the Treatment of Communicating Pediatric Hydrocele." Children (Basel). 2024;11(4):437. — PubMed PMID: 38671654

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9. Connections

• Testicular Cancer
• Testicular Torsion
• Varicocele
• Bladder Cancer
• Kidney Stones
• Enlarged Prostate
• Urinary Tract Infection
• Erectile Dysfunction
• Prostate Cancer
• All Urology Conditions
• Lab Tests
• All Conditions

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