1. Faculty of medicine, Hama University, Hama
2. Faculty of Medicine, Alandalus university, Tartus
3. Faculty of Medicine, Damascus University, Damascus
4. Faculty of Medicine, Cancer Research Center, Tishreen University, Latakia, Syria
5. Faculty of Medicine, Al-Azhar University, Cairo, Egypt
6. Division of Colon and Rectal Surgery, Department of Surgery, Mayo clinic, Rochester, MN