The management of patients with acute gastrointestinal (GI) bleeding is discussed in Chapter 14. Such patients typically have unequivocal evidence of bleeding, such as hematemesis, hematochezia, or melena. However, other patients bleed slowly or intermittently from lesions of the GI tract in a less dramatic manner or in amounts that are insufficient to be clinically evident but may be detected by testing of the stool for occult blood. If bleeding is intermittent, detection and subsequent diagnosis are sometimes difficult. Occult GI bleeding is usually more problematic in patients with occult bleeding disorders (i.e., von Willebrand’s disease). Although the major worry of patients and physicians is that occult bleeding is due to a cancer of the GI tract, the range of causes for the bleeding is virtually the same as that for acute bleeding (see Table 14-1). Occult GI bleeding is often attributed to therapy with anticoagulants or aspirin. However, neither warfarin nor aspirin alone appears to cause positive fecal guaiac-based occult blood tests. A positive fecal blood test of patients on warfarin, heparin, or aspirin should lead to formal evaluation of the GI tract.