Hello,
A hydrocele testis is due to fluid secreted from a remnant piece of peritoneum wrapped around the testis, called the tunica vaginalis.
A common way of diagnosing them is by attempting to shine a strong light through the enlarged testicle or ultrasound testis. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Are you referring to a hydrocele? If so, a hydrocele is a fluid-filled sac surrounding a testicle that results in swelling of the scrotum, the loose bag of skin underneath the penis. Up to 10 percent of male infants have a hydrocele at birth, but most hydroceles disappear without treatment within the first year of life. Additionally, adult men can develop a hydrocele due to inflammation or injury within the scrotum.
More information about hydroceles can be found here:
http://www.medhelp.org/tags/show/3583/hydrocele