1. Department of General, Visceral, and Transplantation Surgery University Hospital of Heidelberg Heidelberg Germany
2. Department of Gynecology and Obstetrics University Medical Centre Mainz Mainz Germany
3. Institute of Medical Biometry University of Heidelberg Heidelberg Germany
4. Department of Biostatistics GCP‐Service International Ltd. & Co. KG Bremen Germany
5. Division of Abdominal Surgery Clarunis‐Academic Centre of Gastrointestinal Diseases St Clara and University Hospital of Basle Basle Switzerland
6. Department of General, Visceral and Thoracic Surgery University Medical Center Hamburg‐Eppendorf Hamburg Germany
7. Department of Urology and Urological Surgery University Medical Center Mannheim University of Heidelberg Mannheim Germany