Accumulation of fluid around the testis
Most common cause of painless scrotal swelling in children
Secondary to persistent processus vaginalis
Most are right sided
Most resorb by 18-24 months of age
Acute symptomatic<unk>  are not benign, require workup
Secondary to persistent processus vaginalis
Hydrocele 
Scrotal cellulitis
Hematocele
Epididymitis
Spermatocele
Fournier gangrene
Varicocele
Inguinal hernia 