1. Clinic for Internal Medicine and Gastroenterology, St. Clemens-Hospital Geldern, Germany
2. Department of Gastroenterology and Hepatology, University Clinic of Essen, Germany
3. Department of Internal Medicine, Knappschaftskrankenhaus, Ruhr-University Bochum, Germany
4. Department of Internal Medicine, St. Josef Hospital, Ruhr-University Bochum, Germany
5. Gastroenterology and Hepatology, Max Grundig Clinic, Bühl/Baden, Bühl, Germany