Filarial Hydrocele

Updated: Feb 17, 2017
  • Author: Bradley Fields Schwartz, DO, FACS; Chief Editor: Edward David Kim, MD, FACS  more...
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Practice Essentials

Lymphatic filariasis, which is colloquially known as elephantiasis, is a parasitic disease caused by the nematodes Wuchereria bancrofti (see the image below), Brugia malayi, and Brugia timori. The adult worms of the species W bancrofti have a predilection for the intrascrotal lymphatic vessels in hosts; thus, hydrocele is the most common manifestation of bancroftian filariasis. In endemic areas, filarial hydrocele is a major cause of disability and disfigurement, as well as a source of direct and indirect economic loss, social stigma, family discord, and sexual burden.

Microfilaria of Wuchereria bancrofti in a peripher Microfilaria of Wuchereria bancrofti in a peripheral blood smear.

Effective treatment for lymphatic filariasis is available, and since 2000 an international program to eliminate the disease has been in progress. Various surgical procedures have been developed to remove the edematous tissue in patients with genital elephantiasis. See Treatment and Medication.


History of the Procedure

Filariasis has been a known disease for thousands of years. The first documentation of this disease was found in Egyptian papyrus prior to 5000 BC. In 1900, Sir Ronald Ross, a scientist from the Liverpool School of Tropical Medicine, reported that lymphatic filariasis is transmitted through mosquito bites. In 1902, Sir Ross was awarded the Nobel Prize in medicine for his discovery that malaria is transmitted to humans through mosquito bites.



The adult worms of Wuchereria bancrofti have a predilection for the intrascrotal lymphatic vessels, and lymphatic obstruction can result in a fluid collection within the tunica vaginalis of the scrotum. Hydrocele is the most common manifestation of chronic W bancrofti infection in males in endemic areas. In females, similar fluid collections can develop along the canal of Nuck. Filarial hydroceles are more difficult to excise surgically than idiopathic hydroceles, because of scarring and fibrosis.




United States

Bancroftian filariasis is endemic in tropical regions throughout the world. In the United States, the disease may be seen in immigrants from these regions and has been reported in military personnel returning from extended deployment to these areas.


The WHO estimates that more than 1.3 billion people in 83 countries and territories are at risk for microfilarial infection. More than 90% of the estimated 120 million infections are due to W bancrofti, of which 26.79 million cases are hydrocele. India bears the greatest burden of this disease, with more than 550 million people at risk. Other endemic areas include the countries of sub-Saharan Africa and Southeast Asia, areas of Latin America, and the Pacific Islands. Prevalence rates of lymphatic filariasis and filarial hydrocele vary. A sample of nearly 5,000 people from 37 districts in Nepal reported a lymphatic filariasis prevalence of up to 40%. [1] A similar study of migrant workers in Myanmar found a prevalence of 2.4%. In endemic countries of Asia and Africa, the prevalence of filarial hydrocele in men older than 45 years commonly exceeds 50%.


No racial predilection for filarial infection has been shown.


The sexual prevalence of filarial infection varies by region, possibly because of variable exposure in cultural or employment patterns that result in contact with vector species of mosquito.


All ages are susceptible to microfilarial infection. Clinical manifestation and acute presentations of lymphatic filariasis increase in prevalence with age. The prevalence of filarial hydrocele also increases with age.



Eight main species of nematodes (roundworms) can cause filariasis; however, the most common is W bancrofti (100 X 0.3 mm), followed by Brugia organisms. The nematodes can live for several years in the lymphatic vessels and lymph nodes. The female worms produce microfilariae (200-300 µm), which circulate in the blood. The microfilariae infect biting Culex pipiens mosquitoes (less commonly Anopheles, Aedes, and Mansonella species). It then develops into the infective filariform larvae within 1-2 weeks. During subsequent bites by the mosquito, the larvae infect human hosts and migrate to the lymphatic tissues, where they develop into adult worms within a year.



Humans are the definitive host of W bancrofti. Numerous species of mosquitoes from the genera Anopheles, Culex, Aedes, and Mansonia serve as the intermediate host. In infected humans, the adult W bancrofti worms are most commonly found in periaortic, inguinal, and intrascrotal lymphatic tissue.

The microfilariae produced by the female worms enter the bloodstream and are ingested by feeding mosquitoes. Once in the mosquito, the juvenile worms pass through 2 larval stages before development halts. Subsequent blood meals taken by the mosquitoes transmit the third-stage larvae into the human dermis. The juvenile worms then migrate to lymphatic tissue in the infected human, where maturation is completed.

While the adult female worms can continue to produce microfilariae in the human host, the adult worm burden cannot increase in the absence of the intermediate host. In endemic areas, filarial infection begins in childhood and the adult worm burden increases upon repeated exposures. Acute presentations most commonly occur in the fourth or fifth decade of life.

Death of the adult worm causes an inflammatory reaction that manifests as acute filarial lymphangitis (AFL). Granulomatous nodule formation and recurrent episodes of AFL impair lymphatic flow, predisposing the host to secondary bacterial infections, which result in fibrosis, lymphatic obstruction, and lymphedema. High-protein lymphedema causes further inflammation and tissue destruction. Once damage is sufficient to overwhelm the lymphatic system, chronic hydrocele ensues.

Laparoscopic view of enlarged lymphatics secondary Laparoscopic view of enlarged lymphatics secondary to filarial infection.

Recent research has implicated the endosymbiotic bacteria Wolbachia as a possible trigger in the immune reaction following the death of adult worms. [2, 3] Release of these obligate intracellular bacteria by the dead adult W bancrofti worm increases the host’s plasma levels of interleukin (IL)–6, IL-10, lipopolysaccharide-binding protein (LBP), and soluble tumor necrosis factor (TNF)–alpha receptors. The exact role of Wolbachia in lymphatic filariasis and the possibility of novel targets for prevention and treatment, including tetracycline antibiotics, have not been fully studied.



Although filarial infection in endemic areas is generally acquired in childhood, the disease may take years to manifest before being diagnosed clinically in early adulthood. Therefore, in endemic areas, up to 50% of the population (more commonly men) may have subclinical infection and may develop pathologic sequelae (although rare). This is characterized by the presence of thousands or millions of parasites in the blood. However, this small number of infections in endemic areas with pathologic changes accounts for the bulk of clinical disease.

Many individuals with filarial infection develop fever due to immune reactions. Patients present with episodic fever associated with lymphangitis, lymphadenitis, funiculoepididymitis (ie, inflammation of the spermatic cord and epididymis), transient edema, and small hydroceles. Patients with secondary infections may also present with fever and a purulent reaction.

The hallmark of clinical disease is lymphedema. Patients in the prepatent period (50-150 d) may develop acute lymphedema of the scrotum that remits spontaneously or after medical treatment. In these patients, lymphatic tissues show typical changes of filarial infection, but adult worms are rarely found.

In contrast, patients with established infections develop permanent lymphatic scarring, resulting in progressive lymphedema. The genitals and lower extremities are the areas most commonly affected.

Elephantiasis of the penis and scrotum in patients with filariasis is the most common clinical problem encountered by urologists. Secondary bacterial infections of the skin and local lymph nodes are common in these patients. Although bacteria play no role in chyluria or filarial hydrocele, elephantiasis and lymph scrotum are often superinfected. Bacterial or fungal infections (most commonly streptococci) lead to recurrent lymphangitis, erysipelas, chronic ulcers, or persistent fungal crusting, aggravating the clinical conditions.

Chyluria develops before elephantiasis in young adult patients. Chyluria results from obstruction of the retroperitoneal lymphatic channels, leading to dilatation and rupture in the urinary collecting system. Initially, chyluria may alarm patients; however, subsequently, it may be disregarded. Occasionally, urinary protein loss may be significant and may lead to hypoalbuminemia and anasarca. Most cases of chyluria are intermittent and respond to bed rest and abdominal binders to increase intra-abdominal pressure. Retrograde lymphangiography and lymphosclerosis can be used in an attempt to treat persistent cases.

Filarial hydroceles (see the images below) vary significantly in size. They can grow very large and may become socially unacceptable and cause significant morbidity and discomfort. Differentiating filarial hydrocele from idiopathic hydrocele is difficult in many cases. A history of exposure to infection from traveling to or residency in endemic areas is suggestive. The World Health Organization (WHO) estimates 69% of all hydroceles are filarial in origin. Since the prevalence of hydroceles in non-endemic areas is considerably low, all patients with hydroceles in W. bancroftiendemic areas should be should be examined for other manifestations of filariasis. [4]

Unilateral left hydrocele and testicular enlargeme Unilateral left hydrocele and testicular enlargement secondary to Wuchereria bancrofti infection in a man who also was positive for microfilariae.
Bilateral hydrocele, testicular enlargement, and i Bilateral hydrocele, testicular enlargement, and inguinal lymphadenopathy secondary to Wuchereria bancrofti infection in a man who also was microfilaremic.

Patients with filarial hydroceles often have a thickened spermatic cord and epididymis with firm nodules. During surgery, the tunica is thickened with calcifications in the wall, and the hydrocele fluid is milky. These findings are uncommon in patients with uncomplicated idiopathic hydroceles. Microfilariae and adult worms are rarely detected in hydrocele fluid.

Lymphocele of the right spermatic cord. Lymphocele of the right spermatic cord.

To guide surgical management, Capuano and Capuano have proposed a standardized clinical classification of filarial hydroceles, based on four criteria [5] :

  • Type – Unilateral versus bilateral

  • Side (left/right)

  • Scrotal enlargement - Rated from I to VI

  • Grade of burial of the penis – Rated from 0 to 4

For size of the scrotum, the rating scale is as follows:

  • Stage I: Smaller than a tennis ball

  • Stage II: Larger than of a tennis ball up and down; the lower pole of the scrotum does not reach halfway down the thigh (between the lower edge of the great trochanter and the upper edge of the patella)

  • Stage III: The lower pole of the scrotum reaches the area between mid-thigh and the knee (upper edge of the patella

  • Stage IV: The lower pole of the scrotum reaches the area between the upper edge of the patella and the lower edge of the knee (tibial tuberosity)

  • Stage V: The lower pole of the scrotum reaches the area between the lower edge of the knee (tibial tuberosity) and the middle of the lower leg

  • Stage VI: The lower pole of the scrotum reaches the area between mid-leg and the ankle (bi-malleolar line)

For burial of the penis, which can be assessed with the patient standing or lying down, the rating scale is as follows:

  • Grade 0: No apparent burial; penis length is within normal limits

  • Grade 1: Partial burial; the length of the visible part of the penis is > 2 cm

  • Grade 2: More important partial burial; the length of the visible part of the penis is < 2 cm

  • Grade 3: Total burial; the prepuce, or the tip of the glans penis if the patient is circumcised, is visible and flush with the surface of the scrotum

  • Grade 4: Total burial; the glans penis is invisible, and the burial cannot be reduced and causes micturition problems



Contrary to the conclusions in previous literature, a 2001 double-blind study in Tanzania found that medical treatment with diethylcarbamazine (DEC) does not affect hydrocele size. [6]

Surgery is the treatment of choice for filarial hydrocele. Indications for hydrocele surgery include the following:

  • Medical ineligibility due to untreated hydroceles

  • Interference with work

  • Interference with sexual function

  • Interference with micturition

  • Negative impact on the patient’s family

  • Dragging pain

  • Susceptibility to trauma because of the patient’s work or mode of transport

  • Possible effect on the testis of long-standing hydroceles



Because of the scarcity of information regarding surgical treatment of filarial hydrocele, clear contraindications have not been elucidated. Standard contraindications to surgical procedures probably apply.