Occult gastrointestinal bleeding.

Occult gastrointestinal bleeding commonly manifests as iron deficiency anemia or fecal occult blood. Iron deficiency anemia results from chronic occult gastrointestinal bleeding. Evaluation of asymptomatic patients who have iron deficiency anemia or fecal occult blood usually should begin with investigation of the colon. Colonoscopy is preferred, but flexible sigmoidoscopy plus air contrast barium enema, or computed tomographic colonography may be acceptable in certain circumstances. If evaluation of the colon does not reveal a bleeding site, evaluation of the upper gastrointestinal tract is mandatory in patients who have iron deficiency anemia, and this should be considered in those who have fecal occult blood. In patients who have gastrointestinal symptoms, evaluation of the portion of the gastrointestinal tract from which the symptoms is derived should be pursued initially. The role of small intestinal investigation is controversial, and this probably should be reserved for patients who have iron deficiency anemia and persistent gastrointestinal symptoms or those who fail to respond to appropriate therapy. Celiac sprue should be considered as a potential cause of iron deficiency anemia in all patients. The treatment and prognosis of patients who have iron deficiency anemia or fecal occult blood depends on the gastrointestinal tract abnormality(ies) identified. Those without identifiable bleeding sites generally respond to conservative management and have a favorable prognosis. On the other hand, the outlook is poorer for patients with refractory occult blood loss or those who have vascular ectasias. Both groups of patients are clinically challenging and require a focused and experienced team approach to diagnosis and therapy.