Occult gastrointestinal (GI) bleeding is bleeding from the GI tract that is not noticeable to patients or physicians. Patients with unexplained anemia (ie, not attributable to another cause such as menstrual bleeding), particularly iron deficiency anemia, should be evaluated for occult GI bleeding. Similarly, if fecal blood is detected during routine colorectal cancer screening, an evaluation for occult bleeding is indicated. Direct visualization with colonoscopy or esophagogastroduodenoscopy are the initial tests of choice; which one is conducted first depends on a patient’s risk factors for upper versus lower GI bleeding. If initial endoscopy is negative, repeat endoscopy may identify the bleeding source. If still negative, other tests, typically capsule endoscopy, can be used to evaluate for small bowel bleeding. Management of identified lesions varies, but they often are amenable to endoscopic intervention or medical management. The need for transfusion is uncommon in occult GI bleeding. Rarely, a surgical approach to visualization and resection may be undertaken. If no bleeding source is identified, or even if it is identified and successfully treated, patients should be evaluated for conditions or treatments that might increase the risk of rebleeding (eg, nonsteroidal anti-inflammatory drug use, antiplatelet/anticoagulant therapy). Need for these treatments should be reevaluated.

Case 1. EW is a 75-year-old man who comes to your office, saying he has been “feeling more run down than usual over the past few months.” History includes stroke, diabetes, chronic obstructive pulmonary disease, and atrial fibrillation. Drugs include aspirin and apixaban. Laboratory test results show that the hemoglobin level has decreased from 11.5 g/dL 1 year ago to 7.2 g/dL today. Mean corpuscular volume is low at 70 mcm³ .