Gastrointestinal causes of refractory iron deficiency anemia in patients without gastrointestinal symptoms

The standard evaluation of a patient with iron deficiency anemia includes a complete evaluation of the gastrointestinal tract to identify a source of bleeding. However, even after a careful examination, many patients remain without a diagnosis. Because iron deficiency anemia results from iron loss or defective absorption, we sought to determine the prevalence of potential gastrointestinal sources for iron deficiency anemia in patients without gastrointestinal symptoms.

Over a 10-month period, 668 outpatients were referred to the University Hematology Department with iron deficiency anemia, defined by a hemoglobin concentration less than 14 g/dL (less than 12 g/dL in women), mean corpuscular volume less than 80 fL, and ferritin level less than 30 microg/L. After excluding patients with obvious causes of blood loss, inadequate diet, chronic diseases, or malignancies, there were 81 eligible patients, 10 of whom refused investigation. The remaining 71 patients (51 women, median age 59 years) underwent colonoscopy, as well as gastroscopy with gastric (antrum and body) and duodenal biopsies.

A likely cause of iron deficiency anemia was detected in 60 patients (85%). Diseases associated with bleeding were found in 26 patients (37%), including colon cancer (10 patients), gastric cancer (2), peptic ulcer (7), hiatal hernia with linear erosions (5), colonic vascular ectasia (3), colonic polyps (2), and Crohn's disease (1). Causes not associated with bleeding were found in 36 patients (51%), including 19 with atrophic gastritis, 4 with celiac disease, and 13 with Helicobacter pylori gastritis. Six (8%) patients had coincident gastrointestinal findings, and 11 (15%) had no cause identified. Patients with an identified nonbleeding-associated cause were younger than those with a bleeding-associated cause (median, 56 vs 70 years; P = 0.001) and included 59% of women (n = 30) versus 30% of men (n = 6) (P = 0.04). Hemoglobin level was not related to the site and severity of disease.

Gastrointestinal diseases that do not usually cause bleeding are frequently associated with iron deficiency anemia in patients without gastrointestinal symptom or other potential causes of gastrointestinal bleeding.