must have had his appendix removed.
remember a few years ago, i think it was a tournament in miami, wherein guille had to quit due to back pains but further tests found that he had gall stones? i can't quite remember the exact story though..
Kidney stones (which is better than having gall stones!!). But the stones were broken up with ultra sonic waves so they could be passed during urination.
Anyway, we need to look at more shirtless pics to see if it really is a scar. how about these
? meh, they're too far away, but still nice to look at