1. Division of Gastroenterology, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Uijeongbu St. Mary's Hospital, 65-1 Geumo-dong, Kyunggi-do, Uijeongbu City 480-717, Republic of Korea
2. Division of Gastroenterology, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul St. Mary's Hospital, 505 Banpo-dong, Seocho-gu, Seoul 137-701, Republic of Korea
3. Division of Gastroenterology, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Bucheon St. Mary's Hospital, 327 Sosaro, Wonmi-gu, Bucheon 420-717, Republic of Korea