1. Department of General Surgery, Cantonal Hospital of Lucerne, Spitalstrasse, 6000 Lucerne 16, Switzerland
2. Clarunis, Department of Visceral Surgery, University Centre for Gastrointestinal and Liver Diseases, St. Clara Hospital and University Hospital, Basel Kleinriehenstrasse 30 4058, Switzerland
3. Department of General Surgery, Cantonal Hospital of Nidwalden, Ennetmooserstrasse, 6370 Stans, Switzerland