1. Department of Surgery, Technische Universität München, Munich, Germany
2. Department of General, Thoracic and Vascular Surgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
3. Department of Surgery, Krankenhaus Bad Cannstatt, Klinikum Stuttgart, Stuttgart, Germany
4. Institute of Medical Statistics and Epidemiology, Technische Universität München, Munich, Germany