It is often caused by fluid collecting within a layer wrapped around the testicle, called the tunica vaginalis, which is derived from peritoneum.

[1] Primary hydroceles may develop in adulthood, particularly in the elderly and in hot countries, by slow accumulation of serous fluid.

[citation needed] A hydrocele can also be the result of a plugged inguinal lymphatic system caused by repeated, chronic infection of Wuchereria bancrofti or Brugia malayi, two mosquito-borne parasites of Africa and Southeast Asia, respectively.

[citation needed] A hydrocele can be produced in four ways: The swelling is soft and non-tender, large in size on examination, and the testis cannot usually be felt.

However the long continued presence of large hydroceles causes atrophy of testis due to compression or by obstructing blood supply.

A common method of diagnosing a hydrocele is by attempting to shine a strong light (transillumination) through the enlarged scrotum.

[citation needed] Secondary hydroceles due to testicular diseases can be the result of cancer, trauma (such as a hernia), or orchitis (inflammation of testis), and can also occur in infants undergoing peritoneal dialysis.

[4] Hydroceles that persist after the first year or occur later in life require treatment only in selected cases, such as patients who are symptomatic with pain or a pressure sensation, or when the scrotal skin integrity is compromised from chronic irritation; the treatment of choice is surgery and the operation is conducted via an open access technique aiming to excise the hydrocele sac.

Local infiltration anesthesia is not satisfactory because it cannot abolish abdominal pain due to traction on the spermatic cord.

[citation needed] Sclerotherapy is an alternative; after aspiration, 6% aqueous phenol (10–20 ml) together with 1% lidocaine for analgesia can be injected, and this often inhibits reaccumulation.

These alternative treatments are generally regarded as unsatisfactory because of the high incidence of recurrences and the frequent necessity for repetition of the procedure.