Study of Ischemic Colitis Compared to Other Diagnoses in Patients With Lower Gastrointestinal Bleeding

Inclusion Criteria: * bright red blood clots or burgundy colored stool documented by a health care worker * clinical or laboratory evidence of significant blood loss, manifested by any one of the following: (a) more than three bloody bowel movements in eight hours (b) a decrease of two grams of hemoglobin (Hgb) from baseline, or (c) transfusion of more than three units of red blood cell (URBC). Exclusion Criteria: * age less than 18 year * history of inflammatory bowel disease * hypotension or shock refractory to resuscitation * severe coagulopathy refractory to resuscitation (platelet count \< 30,000; prothrombin time \[PT\]- more than 2 times normal; partial thromboplastin time \[PTT\]- more than 2 times normal) * acquired immune deficiency syndrome or neutropenia * the inability to provide informed consent * documentation of anal disorders as a cause of bleeding such as internal hemorrhoids, anal fissures, polyps or cancer of the anal canal, and fistulae