This is a new one to me. I would just guess that a saline injection is not going to do much or last that long. Saline is simply water with salt and maybe some other minerals in it. Your body would rapidly absorb the water. (The Saline breast implants are in a bag, and then implaced in the breast) I would consult your doctor, there is a possibility of adding a fake testes, and this would give you the bulk you are wanting. They use the fake testes to replace those removed, to make the scrotum appear normal.