A hydrocele is a small sac of fluid that forms inside a person's body, often near the male testis. The fluid in a hydrocele typically builds up over time. Hydroceles are common in infants and small children, and the fluid comes from the abdominal cavity.
Because of their location and the swelling involved, hydroceles are often confused with hernias. Doctors sometimes even refer to them as hydrocele hernias. When a hydrocele is small and doesn't grow, it tends to resolve on its own. For larger or growing hydroceles, a surgical procedure is often necessary. The procedure involves removal of the fluid and reinforcement of the muscle wall to prevent further problems.