Final answer:
A hydrocele is a fluid-filled sac in the scrotum, with communicating hydroceles having a connection to the abdominal cavity, allowing fluid flow, while noncommunicating hydroceles are isolated and have no such connection.
Step-by-step explanation:
A hydrocele is a fluid-filled sac surrounding a testicle that results in swelling of the scrotum. There are two main types: communicating and noncommunicating hydroceles.
Communicating hydroceles are caused by a patent (open) processus vaginalis, which is an outpouching of the peritoneum (the lining of the abdominal cavity). Normally, the processus vaginalis closes off shortly after birth, but if it remains open, fluid from the abdominal cavity can flow into the scrotum and cause a hydrocele.
Noncommunicating hydroceles occur when the fluid is trapped between layers of the processus vaginalis that is no longer connected to the abdominal cavity. The fluid is often from a remnant of the processus vaginalis that has sealed off, which can happen before or shortly after birth.
In summary, the main difference lies in the communication of the hydrocele with the abdominal cavity. Communicating hydroceles have a direct connection, allowing fluid to flow between the scrotum and the abdomen, whereas noncommunicating hydroceles do not have this connection and the fluid is confined to the scrotum.