Ali Kabir1, Mehrdad Moghimi2, Afshin Amini3. 1. Gastrointestinal and Liver Disease Research Center, Iran University of Medical Sciences Tehran, Iran ; Department of Epidemiology,Faculty of Public Health, Shahid Beheshti University of Medical Sciences Tehran, Iran. 2. Department of Surgery, Shahid Beheshti University of Medical Sciences Tehran, Iran. 3. Department of Toxicology and Emergency Medicine, Imam Hossein Hospital, Faculty of Medicine, Shahid Beheshti University of Medical Sciences Tehran, Iran.