DiGregorio Alexander M., Alvey Heidi
Wright State University Boonshoft School of Medicine
Baylor Scott & White/Texas A&M SOM
Gastrointestinal bleeding can fall into two broad categories: upper and lower sources of bleeding. The anatomic landmark that separates upper and lower bleeds is the ligament of Treitz, also known as the suspensory ligament of the duodenum. This peritoneal structure suspends the duodenojejunal flexure from the retroperitoneum. Bleeding that originates above the ligament of Treitz usually presents either as hematemesis or melena whereas bleeding that originates below most commonly presents as hematochezia. Hematemesis is the regurgitation of blood or blood mixed with stomach contents. Melena is dark, black, and tarry feces that typically has a strong characteristic odor caused by the digestive enzyme activity and intestinal bacteria on hemoglobin. Hematochezia is the passing of bright red blood via the rectum.
上消化道出血和下消化道出血。区分上消化道出血和下消化道出血的解剖标志是Treitz韧带，也称为十二指肠悬韧带。这个腹膜结构将十二指肠空肠曲从后腹膜悬吊起来。Treitz韧带以上部位的出血通常表现为呕血或黑便，而其以下部位的出血最常见的表现为便血。呕血是指血液或与胃内容物混合的血液反流。黑便是黑色、焦油样粪便，通常因血红蛋白上的消化酶活性和肠道细菌而具有强烈的特征性气味。便血是指鲜红色血液经直肠排出。
