what is your provisional diagnosis ? add your medical diagnosis as a comment below and i will add the right answer after few days
hydrocele. if you look at the right leg you will notice it is also very swolen yet no other body parts are swolen or have any other deformations ruling out spermatocele which would only affect the testes and show up in the scrotum. elephantitus affects bones as well as tissue and i can see no other deformations around the immediate scrotal area. i would guess the hydrocele started in the right leg and moved into the scrotum.