Overview of Gastrointestinal Bleeding
Bleeding is a common symptom of both benign and malignant disorders of the digestive system. Bleeding, even in the absence of other digestive tract symptoms such as pain, obstruction, or signs of perforation, always warrants a definitive evaluation because it may lead to a life-threatening loss of blood and is often associated with significant and/or potentially lethal disorders. The more evidence there is of bleeding (anemia, iron deficiency, or overt bleeding) the greater the likelihood that a serious disorder is present. Advanced malignancies are common causes of bleeding, but most causes are benign and treatable with medication and/or endoscopic techniques.
Evaluation of the cause of bleeding includes consideration of the location of gastrointestinal bleeding; one must also assess the severity and rapidity of blood loss. Blood loss from the digestive tract is described as overt when there is obvious bleeding and occult when bleeding can only be detected by stool testing, a drop in hemoglobin, or iron deficiency.
Overt bleeding from the upper digestive system presenting as the vomiting of bright-red blood is hematemesis. Partially digested blood that has turned black appears in vomitus as black strands of mucoid material or small specks of black described as coffee ground emesis. Bright-red blood expelled from the rectum is hematochezia. Passage of black stool from overt bleeding is melena, which has a distinctive odor well known to gastroenterologists and emergency physicians as an urgent call for prompt intervention. Hematochezia may be seen as droplets or staining of the toilet paper when it originates from rectal cancer or hemorrhoids, or it may fill the toilet bowel. In either situation, endoscopic diagnosis of the cause is necessary.
Bleeding is often not recognized until a patient is found to be anemic by physical examination or laboratory tests. Iron deficiency in males of any age and all non menstruating females is commonly due to bleeding. Although iron deficiency in premenopausal women is more commonly due to menstruation, gastrointestinal bleeding should always be considered. Malabsorption is also a common cause of iron deficiency. This is particularly common in patients with celiac disease and chronic gastric hypochlorhydria whether due to severe atrophic gastritis or to chronic use of high-dose proton pump inhibitors. Differentiating occult bleeding from malabsorption is facilitated by point-of-service stool testing for blood with paper tests that react to the presence of any oxidating substance (stool guaiac test) or immune reactions (fecal immune test for hemoglobin); the latter test is much more specific but less sensitive for upper gastrointestinal sources and more expensive. When blood is found, a diagnosis should always be sought. Distinguishing between occult bleeding and malabsorption is difficult because bleeding from most lesions is intermittent. For example, in patients with known colon cancer extensive enough to require surgical resection, only one in four stool tests for occult blood will be positive. The limited sensitivity of these tests necessitates repeating stool examinations in four to six specimens 2 or 3 days before one can be confident there is no active bleeding. Repeat testing of stools, hemoglobin levels, and iron levels; keen judgment; and close follow-up are necessary when evaluating patients with suspected occult bleeding.
The most challenging patients are those who have documented bleeding but for whom a definitive cause is elusive. The term occult gastrointestinal bleeding is used to describe such patients, including patients who have had a high-quality evaluation with both endoscopy and a well-prepped colonoscopy by an expert. When obscure bleeding is finally diagnosed, it is usually found by endoscopy or colonoscopy, because lesions may be intermittent or even lead to bleeding in the absence of an obvious break in the mucosa, as occurs with Dieulafoy lesions. If endoscopy and colonoscopy results are negative, techniques must be used that extend beyond the reach of these standard procedures, including capsule endoscopy, push enteroscopy, or single or double balloon enteroscopy. Radiographic tests that may be of value in the evaluation of such patients include nuclear medicine bleeding scans, angiography, and crosssectional i aging with computerized tomography (CT) scanning.