What is the composition in hydrocele fluid ?

Serous fluid.: Hydrocele fluid is similar to other tissue fluids in the body, such as peritoneal fluid. It is a solution of mostly water, electrolytes, and protein. A 1994 study revealed that hydrocele fluid had higher levels of calcium, albumin, total protein and creatine-kinase, and lower levels of potassium, aspartate transaminase, and alkaline phosphatase than blood serum.

See below: Hydrocele fluid is similar to peritoneal fluid. It contains water and a plasma exudate such as albumin, electrolytes, calcium etc at very low levels. It may also contain cells such as white blood cells or blood.

Increased protein: Composition of hydrocele fluid is similar in electrolyte & cemical content to serum (non cellular, fluid component of blood) except that it contains more protein. This may explain why non communicating hydroceles develop in the first place, or at least fail to resolve spontaneously. Also contains more phosphate which is probabably coincidental.