Hydrocoele - the swelling of the scrotum/testis. what can cause it?

Connection: The testis are formed near the kidneys & migrate down into the scrotum over time. During descent they leave the abdomen in a tubular projection of a lining of the abdominal wall called the peritoneum, which adheres to the testis & blood vessels like shrink wrap. If the shrink wrap doesn't shrink enough, clear abdominal fluid can end up in the scrotum next to the testis.

Fluid: Hydrocele is fluid trapped within the scrotum. In a newborn most will resolve by age 12-18 months. If hydrocele appears latter in life then it is a sign of communication between scrotum and abdomen, as in hernia.

Adult or child?: Most scrotal hydroceles in infants or children are due to a patent processus vaginalis (peritoneal communication) which usually close sponteously by age-1-year. Many do not close on their own & require inguinal repair like a hernia. Adult type hyrdoceles r caused by tunica vaginalis (normal scrotal envelope) secreting > hydrocele fluid than is absorbed, usually benign but can be caused by tumor.