RT Book, Section A1 Sheu, Eric G. A1 Tavakkoli, Ali A2 Zinner, Michael J. A2 Ashley, Stanley W. A2 Hines, O. Joe SR Print(0) ID 1160038832 T1 Gastrointestinal Bleeding T2 Maingot's Abdominal Operations, 13e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9780071843072 LK accesssurgery.mhmedical.com/content.aspx?aid=1160038832 RD 2024/03/29 AB Acute gastrointestinal (GI) bleeding is a common problem causing significant morbidity and mortality. The source of GI bleeding can be anywhere in the GI tract, from the esophagus to the rectum. GI bleeding is classified into upper or lower bleeding based on the site of bleeding relative to the ligament of Treitz. Upper GI hemorrhage occurs from sites proximal to the ligament of Treitz and accounts for more than 80% of acute bleeding.1 Lower GI bleeding originates distal to the ligament of Treitz, most commonly from the colon. The small intestine is the site of bleeding in less than 5% of patients.1 Hemorrhage persisting or recurring after negative endoscopy is termed obscure bleeding. Occasionally patients present with occult bleeding, where there are no signs of overt bleeding but only symptoms of chronic blood loss anemia. In all cases, thorough investigation to localize the source of bleeding allows rapid and often definitive management.