Hey,
um not to be too pedantic or anything, but abdominal hernia isn't really the correct term. What it sounds like is an indirect inguinal hernia. It's a funny thing how since your balls and a woman's ovaries are equivalents, the structures originated in the same place. Before birth, your balls take on a sort of epic journey to reach the scrotum. If you're at all interested, they move from a position 'inside your belly' to nearer the surface (to about halfway between your dick and your hip bone 'point', or ASIS, more techincally.) Here, they enter the inguinal canal (a tube of connective tissue, bascially) and move down that groove between your hip and your pubic area. (That cord you can feel there is called the inguinal ligament; this canal runs with it.) The canal ends as it approaches your dick, then your balls continue into the scrotum.
What ought to happen is that pathway should close up behind your balls. If it remains open - or patent, as we call it - then your viscera (guts) can enter you balls and vice versa. This is a congenital condition and called a indirect inguinal herna.
A direct inguinal hernia happens basically when you become quite fat and your gut contents put pressure on your (weak and untoned) ab muscles. There is an area of weakness in the covering sheath, and if the pressure if sufficient, your viscera will protrude through, following the path your balls took long ago, from the point after leaving the inguinal canal. That is, your guts independently squeeze down into your balls.
I'm sorry if that's not a great description; I learnt about all this months ago, but this stuff (anatomy) was always a strong suit, so I think it's all right.