1. Department of General, Visceral, and Transplantation Surgery, Muenster University Hospital, 48149 Muenster, Germany
2. Department of Surgery, Klinikum rechts der Isar, Technical University of Munich School of Medicine, 81675 Munich, Germany
3. Department of Statistics, Chair of Statistical Methods in Social Sciences, Technical University of Dortmund, 44227 Dortmund, Germany
4. Psychological Assessment and Methods Group, Institute of Psychology, Faculty of Educational Sciences, University of Duisburg-Essen, 45141 Essen, Germany
5. Medizinisches Versorgungszentrum Portal 10, 48155 Muenster, Germany