Excerpt from Gastrointestinal Bleeding, Lower

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Background

Lower gastrointestinal (GI) hemorrhage is defined as bleeding from the bowel distal to the ligament of Treitz. Acute lower GI bleeding is of recent onset and results in hemodynamic instability and decreasing hemoglobin levels, which need to be treated with transfusions.

During recent years, colonoscopy has emerged as the procedure of choice, but angiography still remains the best option in a patient in unstable condition. In cases in which colonoscopy is unsuccessful, scanning during episodes of bleeding and arteriography are considered to be next imaging tests to determine the cause of the bleeding. Arteriography also provides therapeutic options. This article reviews the current recommendations for work-up and management of acute lower GI bleeds.

For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles, Gastrointestinal Bleeding and Rectal Bleeding.

Pathophysiology

The causes of acute lower GI bleeding include diverticulosis, angiodysplasia, colon cancer, colitis (including infectious, ischemic, or radiation-induced forms), inflammatory bowel disease, polyps, Meckel diverticulum, and aortoenteric fistula. Hemorrhoids are probably the most common cause of lower GI bleeding, but they usually do not pose difficulties in the diagnosis and they rarely cause massive bleeding. Similarly, anorectal fissures can bleed, but again, these are easily diagnosed on the basis of the history and the clinical findings.

Lower GI bleeding appears as the passage of bright red blood per rectum. In about 10-15% of cases, the cause may be proximal to the ligament of Treitz. In these cases, nasogastric tube placement is frequently needed to confirm that the upper GI tract is the source of the bleeding.

The most common cause of lower GI bleeding involves the colonic diverticula. In 1976, Myeres et al reported on the pathogenesis of bleeding diverticula. They showed asymmetric rupture of the vasa recta at the dome of the diverticulum, with intimal eccentric thickening and medial thinning at or near the bleeding point. Comparing this with control diverticula, they suggested that traumatic injury may play a role in predisposing the diverticula to bleeding and rupture. Diverticulosis has been implicated as the source of bleeding in as many as 60% of cases of lower GI bleeding. The diverticula are more prevalent in the left or sigmoid colon, but positive arteriographic findings for bleeding localizes the bleeding to the right colon in 60% of cases.

Angiodysplasia has an incidence of 1-2%; this involves ectatic vessels in the mucosa and submucosa of the GI tract. At endoscopy, they appear as red, flat lesions, and a feeding vessel is sometimes shown. These vessels are reported to be responsible for 3-12% of cases of acute lower GI bleeding. The majority are present in the right colon. An association with various systemic diseases has been described; these diseases include aortic stenosis, von Willebrand disease, chronic obstructive pulmonary disease (COPD), cirrhosis, chronic renal disease, and collagen vascular disease.

Other causes of lower GI bleeding include neoplasia, such as a polyp or carcinoma. Significant bleeding can also occur in about 2-4% of cases after endoscopic removal of polyps from the colon, though other studies have shown lower rates. Inflammatory bowel disease and other types of colitis account for as many as 30% of cases of acute lower intestinal bleeding. Less frequent causes of acute colorectal bleeding include solitary rectal ulcer, portal colopathy, Dieulafoy lesions of the colon, endometriosis, and colonic varices.

Please click here to view the full topic text: Gastrointestinal Bleeding, Lower