1. Uniklinik Aachen, General-, Visceral- and Transplant Surgery, Pauwelsstr. 30, 52074 Aachen, Germany
2. Uniklinik Aachen, Gastroenterology, Metabolic Diseases and Internal Intensive Care Medicine, Pauwelsstr. 30, 52074 Aachen, Germany
3. Uniklinik Essen, General-, Visceral- and Transplant Surgery, Hufelandstr. 55, 45147 Essen, Germany
4. Gemeinschaftskrankenhaus Bonn, General- and Visceral Surgery, Prinz-Albert-Str. 40, 53113 Bonn, Germany