1. Unit of General and Emergency Surgery, Papa Giovanni XXIII Hospital, Bergamo, Italy.
2. Unit of General Surgery, Infermi Hospital, Rimini, Italy.
3. Unit of General and Emergency Surgery, Macerata Hospital, Macerata, Italy.
4. Unit of General and Emergency Surgery, Parma University Hospital, Parma, Italy.
5. Department of Medical Sciences, University of California, Berkeley, California.