1. Division of Gastroenterology and Hepatology, Dessau Municipal Hospital, Auenweg 38, Dessau-Rosslau, Germany
2. Digestive Center for Diagnosis and Treatment, Damascus, Syrian Arab Republic
3. Division of Gastroenterology, John T. Milliken Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
4. Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
5. Department of Colorectal Surgery, Cleveland Clinic, Cleveland, OH, USA
6. Division of Colon and Rectal Surgery, Mayo Clinic, Rochester, MN, USA
7. Robert D and Patricia E Kern Center for the Science of Health Care Delivery, Mayo Clinic, Rochester, MN, USA
8. Division of Gastroenterology, Massachusetts General Hospital, Boston, MA, USA