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For further information, see CMDT Part 15-07 Gastrointestinal Bleeding

Key Features

  • Positive fecal occult blood test (FOBT), fecal immunochemical test (FIT), or iron deficiency anemia in an adult with no visible fecal blood loss

  • 2–6% of patients in screening programs have a positive FOBT or FIT

  • 2% of men and 5% of women have iron deficiency anemia

  • In premenopausal women

    • Most common causes: menstrual and pregnancy-associated iron loss

    • GI blood loss in 10%

    • No cause determined in 30–50%

  • In men and postmenopausal women

    • Colonic blood loss in 15–30%

    • Upper GI blood loss in 35–55%

    • Malignancy in the lower gastrointestinal tract in 8.9% and upper tract in 2.0%

  • Most common causes of occult blood loss

    • Neoplasms

    • Vascular abnormalities (angioectasias)

    • Acid-peptic lesions

    • Infections (nematodes [especially hookworm], tuberculosis)

    • Medications (especially NSAIDs or aspirin)

    • Inflammatory bowel disorder or malabsorption (celiac disease)

Clinical Findings

  • Positive FOBT or FIT test

  • Iron deficiency anemia


  • Colonoscopy with or without upper endoscopy is indicated

    • For all adults with positive FOBT or FIT test or iron deficiency anemia

    • For premenopausal women and younger men with GI symptoms

    • For those with family history of GI cancer

    • For women with anemia disproportionate to the estimated menstrual blood loss

  • Colonoscopy should be done first unless upper GI tract symptoms are present

  • Further investigation of the small intestine is recommended in patients who have

    • Anemia that responds poorly to empiric iron supplementation

    • Signs of ongoing bleeding (fecal occult blood)

    • Worrisome symptoms (abdominal pain, weight loss)

  • Capsule endoscopy is recommended as the initial study in most patients to look for vascular ectasias and to exclude a small intestinal neoplasia or inflammatory bowel disease

  • If a small intestine source is identified, push enteroscopy, balloon-assisted enteroscopy, abdominal CT, angiography, or laparotomy are pursued, as indicated


  • Colonoscopy, upper endoscopy, and small bowel enteroscopy allow

    • Biopsy specimens to be obtained

    • Benign and malignant neoplasms to be excluded

    • Vascular ectasias to be cauterized endoscopically

  • For patients with iron deficiency anemia who have no significant findings on upper endoscopy or colonoscopy and who are without symptoms of small intestinal disease,

    • An initial trial of empiric iron therapy is recommended by the 2020 American Gastroenterological Association guidelines

    • A sustained rise in ferritin and hemoglobin with 1–2 months of iron therapy may obviate the need for further studies

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