1 Department of General Surgery and Digestive System. Royo Villanova Hospital. Zaragoza. Spain. 2 Department of Human Anatomy and Histology. University of Zaragoza. Zaragoza. Spain. 3 Department of Surgery. Jesus Uson Minimally Invasive Surgery Centre. Caceres. Spain. 4 Department of Anatomy, Cell Biology and Zoology. University of Extremadura. Badajoz. Spain. 5 Department of Morphological Sciences and Sociosanitary. University of Cordoba. Cordoba. Spain.