Diagnosis and treatment of unexplained anemia with iron deficiency without overt bleeding

A general overview is given of the causes of anemia with iron deficiency as well as the pathogenesis of anemia and the para-clinical diagnosis of anemia. Anemia with iron deficiency but without overt GI bleeding is associated with a risk of malignant disease of the gastrointestinal tract; upper gastrointestinal cancer is 1/7 as common as colon cancer. Benign gastrointestinal causes of anemia are iron malabsorption (atrophic gastritis, celiac disease, chronic inflammation, and bariatric surgery) and chronic blood loss due to gastrointestinal ulcerations. The following diagnostic strategy is recommended for unexplained anemia with iron deficiency: conduct serological celiac disease screening with transglutaminase antibody (IgA type) and IgA testing and perform bidirectional endoscopy (gastroscopy and colonoscopy). Bidirectional endoscopy is not required in premenopausal women < 40 years of age. Small intestine investigation (capsule endoscopy, CT, or MRI enterography) is not recommended routinely after negative bidirectional endoscopy but should be conducted if there are red flags indicating malignant or inflammatory small bowel disease (e.g., involuntary weight loss, abdominal pain or increased CRP). Targeted treatment of any cause of anemia with iron deficiency found on diagnostic assessment should be initiated. In addition, iron supplementation should be administered, with the goal of normalizing hemoglobin levels and replenishing iron stores. Oral treatment with a 100-200 mg daily dose of elemental iron is recommended (lower dose if side effects), but 3-6 months of oral iron therapy is often required to achieve therapeutic goals. Intravenous iron therapy is used if oral treatment lacks efficacy or causes side effects or in the presence of intestinal malabsorption or prolonged inflammation. Three algorithms are given for the following conditions: a) the paraclinical diagnosis of anemia with iron deficiency; b) the diagnostic work-up for unexplained anemia with iron deficiency without overt bleeding; and c) how to proceed after negative bidirectional endoscopy of the gastrointestinal tract.