Occult Gastrointestinal Bleeding

Occult gastrointestinal bleeding is bleeding that is not visible to the patient or clinician and is detected by a positive faecal occult blood test or by iron deficiency anaemia.

• Daily blood loss of 2 to 10 mL is typical; losses above 2 mL/day turn the faecal test positive.
• Causes: colorectal cancer and polyps, peptic ulcer, erosive gastritis and oesophagitis, gastric cancer, angiodysplasia, hookworm infestation, coeliac disease, NSAID enteropathy, and occasionally Cameron lesions in large hiatus hernias.
• Risk factors: age above 50 years, NSAIDs, aspirin, family history of colorectal cancer, endemic intestinal helminths.

Patients are asymptomatic or have features of anaemia.

• Fatigue, pallor, exertional dyspnoea, palpitations, angina, koilonychia, angular stomatitis, pica.
• Possible dyspepsia, weight loss, change in bowel habit, abdominal mass, or lymphadenopathy.
• Differential diagnosis: other causes of anaemia (chronic disease, haemolysis, malabsorption, dietary deficiency, menorrhagia), false-positive faecal test (red meat, iron, certain vegetables, vitamin C false negatives), nasopharyngeal or respiratory bleeding.
• Complications: symptomatic anaemia, delayed diagnosis of malignancy, heart failure decompensation.

Full blood count and film (microcytic hypochromic), ferritin, transferrin saturation, reticulocyte count.

• Faecal immunochemical test for lower tract screening; the guaiac test can be positive from upper tract blood.
• Bidirectional endoscopy: upper endoscopy with duodenal biopsies (coeliac disease) and colonoscopy, which find a source in about 50 to 60 percent.
• Stool microscopy for hookworm ova in endemic areas.
• If both are normal, proceed to small bowel evaluation with capsule endoscopy; CT enterography for suspected tumour or Crohn disease.

Supportive

• Treat the source identified and replace iron.
• Oral ferrous sulfate 200 mg (65 mg elemental iron) once daily or on alternate days for 3 months after haemoglobin normalises.
• Intravenous iron if intolerance, malabsorption or ongoing losses: ferric carboxymaltose 1000 mg single dose (maximum 20 mg/kg) or iron sucrose 200 mg on 5 occasions.

Pharmacological

• Hookworm: albendazole 400 mg single dose (repeat after 2 weeks if heavy burden).
• Peptic disease: omeprazole 40 mg daily for 8 weeks and eradicate H. pylori if present.
• Stop or substitute NSAIDs; add omeprazole 20 mg daily if aspirin is essential.

Procedures: polypectomy, argon plasma coagulation of angioectasia, resection of tumours.

Special groups: young women with iron deficiency still need upper endoscopy if no clear gynaecological cause; vegetarians and pregnant women need dietary and supplemental iron.

Red flags: age above 50 years, weight loss, family history of colorectal cancer, haemoglobin below 8 g/dL.

Follow-up: haemoglobin at 4 weeks (rise of 2 g/dL expected), ferritin at 3 months; repeat investigation if recurrent anaemia.