1. Department for General, Visceral, Thoracic and Vascular Surgery, University Hospital of Bonn, Bonn, Germany
2. Institute of Experimental Haematology and Transfusions Medicine, University Hospital of Bonn, Bonn, Germany
3. Institute for Medical Biometrics, Informatics and Epidemiology, University Hospital of Bonn, Bonn, Germany
4. Department for General and Visceral Surgery, St. Elisabeth-Hospital Leipzig, Leipzig, Germany