A hydrocele is a painless buildup of watery fluid around one or both testicles that causes the scrotum or groin area to swell. This swelling may be unsightly and uncomfortable, but it usually is not painful and generally is not dangerous.
Hydroceles that appear later in life may be caused by an injury or surgery to the scrotum or groin area. Or they can be caused by inflammation or infection of the epididymis or testicles. In rare cases, hydroceles may occur with cancer of the testicle or the left kidney. This type of hydrocele can occur at any age but is most common in men older than 40.
You may notice enlargement of your scrotum. Symptoms, when present, can include pain, swelling, or redness of the scrotum or a feeling of pressure at the base of the penis.
A hydrocele is usually diagnosed by an exam of the scrotum, which may appear enlarged. As part of the exam, your doctor will shine a light behind each testicle (transillumination). This is to check for solid masses that may be caused by other problems, such as cancer of the testicle. Hydroceles are filled with fluid, so light will shine through them (transillumination).