What are the primary causes of iron deficiency in a 60-year-old man with normal urinalysis, serum protein electrophoresis (SPE), and chest x-ray?

Primary Causes of Iron Deficiency in a 60-Year-Old Man with Normal Urinalysis, SPE, and Chest X-Ray

In a 60-year-old man with iron deficiency anemia, gastrointestinal blood loss is the most likely cause and requires urgent bidirectional endoscopy (upper and lower GI tract examination) to rule out gastrointestinal malignancy. 1

Diagnostic Approach to Iron Deficiency in Older Men

Iron deficiency anemia (IDA) in men over 50 years of age should always prompt a thorough gastrointestinal evaluation, as approximately one-third of men with IDA have an underlying pathological abnormality, most commonly in the GI tract 1. The normal urinalysis, serum protein electrophoresis, and chest x-ray have already ruled out some potential causes but do not eliminate the need for GI investigation.

Common Gastrointestinal Causes in Older Men:

1. Bleeding-associated causes (37% of cases) 2:

   • Colorectal cancer (most common serious cause)
   • Gastric cancer
   • Peptic ulcer disease
   • Hiatal hernia with linear erosions
   • Colonic vascular ectasia (angiodysplasia)
   • Colonic polyps
   • Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
   • NSAID-induced gastrointestinal bleeding

2. Non-bleeding causes (51% of cases) 2:

   • Atrophic gastritis (most common non-bleeding cause)
   • Helicobacter pylori gastritis
   • Celiac disease
   • Gastrectomy or gastric atrophy
   • Bacterial overgrowth

Recommended Investigation Algorithm

1. Confirm iron deficiency:

   • Serum ferritin (most useful marker; <30 μg/L indicates iron deficiency) 1
   • Transferrin saturation (<20% suggests iron deficiency) 3
   • Consider therapeutic trial of iron (Hb rise ≥10 g/L within 2 weeks strongly suggests iron deficiency) 1

2. Initial workup:

   • Detailed history focusing on:
     • Medication use (especially NSAIDs, anticoagulants)
     • Dietary habits
     • Family history of hematological disorders or GI cancers
     • Previous gastric surgery

3. GI evaluation (highest yield in men over 60):

   • Upper GI endoscopy with gastric and duodenal biopsies 1
     • Include screening for celiac disease (found in 3-5% of IDA cases) 1
     • Assess for H. pylori infection
   • Colonoscopy (should be performed even if upper GI endoscopy reveals findings unless colorectal cancer is found) 1
   • Consider bidirectional endoscopy in same session for efficiency 1

Important Clinical Considerations

• In studies of asymptomatic patients with iron deficiency, 44-85% had identifiable GI lesions 2, 4
• Colorectal cancer was found in up to 21% of asymptomatic patients with iron deficiency 4
• Dual pathology (lesions in both upper and lower GI tract) occurs in 10-15% of patients 1
• Findings like esophagitis, erosions, and peptic ulcer should not be immediately accepted as the sole cause of iron deficiency without completing the evaluation 1

Special Considerations

• If initial endoscopic evaluation is negative, consider:
  • Small bowel evaluation (capsule endoscopy) for persistent or transfusion-dependent IDA 1
  • Repeat testing if symptoms persist or anemia recurs after treatment
  • Evaluation for rare causes like Meckel's diverticulum or vascular malformations

Pitfalls to Avoid

1. Accepting minor GI findings as the cause without complete evaluation - Findings like mild gastritis should not prevent completion of the full GI workup 1

2. Assuming dietary deficiency is the cause - While poor dietary intake can contribute, it should not be presumed as the sole cause in men over 60 without a thorough GI investigation 1

3. Misinterpreting laboratory tests - Ferritin can be falsely normal in inflammatory conditions; consider transferrin saturation or therapeutic trial of iron when in doubt 1

4. Stopping at negative initial tests - Up to 15% of patients may have no cause identified on initial evaluation but require follow-up 2