The presence of fluid is demonstrated by transillumination. These hydroceles can reach a huge size, containing large amount of fluid, as these are painless and are often ignored. They are otherwise asymptomatic, other than size and weight, causing inconvenience. However the long continued presence of large hydroceles causes atrophy of testis due to compression or by obstructing blood supply. In most cases, the hydrocele, when diagnosed early during complete physical examination, are small and the testis can easily be palpated within a lax hydrocele. However Ultrasound imaging is necessary to visualize the testis if the hydrocele sac is dense to reveal the primary abnormality. But these can become large in cases when left unattended. Hydroceles are usually painless, as are testicular tumors. A common method of diagnosing a hydrocele is by attempting to shine a strong light (transillumination) through the enlarged scrotum. A hydrocele will usually pass light, while a tumor will not (except in the case of a malignancy with reactive hydrocele). Secondary hydroceles
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. A hydrocele is not a cancer but it should be excluded clinically if a presence of a testicular tumor is suspected, however, there are no publications in the world literature that report a hydrocele in association with testicular cancer. Secondary hydrocele is most frequently associated with acute or chronic epididymo-orchitis.
Local infiltration anesthesia is not satisfactory because it cannot abolish abdominal pain due to traction on the spermatic cord. In long standing cases, hydrocele fluid may be opalescent with cholesterol and may contain crystals of tyrosine.After aspiration of a primary hydrocele, fluid reaccumulates over the following months and periodic aspiration or operation is needed. For younger patients, operation is usually preferred. 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 treatment because of the high incidence of recurrences and the frequent necessity for repetition of the procedure. References
External links

Hydrocele at eMedicine