J.A. Villanueva-Herrero, Professor, Hospital General de Mexico Dr Eduardo Liceaga, Ciudad de Mexico, Ciudad de Mexico, MEXICO|W.S. Pineda-Hernandez, General surgeon, Hospital Medico Quirurgico, San Salvador, San Salvador, EL SALVADOR|N. Somoza, General Surgeon, Hospital Medico Quirurgico, San Salvador, EL SALVADOR|