外科學案例56例：第4版（簡體書）

The passage of maroon-colored stool and blood clots generally indicates acute bleeding from a lower GI tract source (distal to the ligament of Treitz).Maroon-colored stool represents a mixture of fecal material and blood, indicating that the bleeding source is located proximal to the lower rectal segment and anus.The passage of blood clots can occur with brisk bleeding from an upper GI tract source.Placement of an NG tube is useful during the initial evaluation for possible upper GI tract bleeding, although up to 16% of patients may have nonbloody NG aspirate with upper GI tract bleeding originating from the duodenum.In patients older than 40 years, the most likely causes of acute lower GI tract bleeding are diverticulosis, angiodysplasia, and neoplasm, and these lesionsare generally painless.When lower GI tract bleeding occurs in the presence of abdominal pain, the possibility of an ischemic bowel, inflammatory bowel disease, intussusception, and a ruptured abdominal aneurysm should be entertained.Following resuscitation, the primary goal in the treatment of a patient with acute and continued lower GI tract bleeding is localization of the bleeding site (colonoscopy, mesenteric angiography, and/or an isotope-labeled red blood cell (RBC) scan).