What tests are used to determine the source of blood loss in a case of Iron Deficiency Anemia (IDA)?

Diagnostic Workup for Iron Deficiency Anemia in a 48-Year-Old Male

In a 48-year-old male with iron deficiency anemia, you should perform bidirectional endoscopy (gastroscopy and colonoscopy) as first-line investigation, along with urinalysis and coeliac disease screening. 1

Initial Assessment

History and Basic Testing

• Take a detailed history focusing on:

  • NSAID or aspirin use (stop if possible) 1
  • Dietary iron intake (though dietary deficiency alone should not preclude full GI investigation) 1
  • Family history of bleeding disorders or telangiectasia 1
  • Symptoms of GI bleeding (though symptoms rarely correlate with findings) 1

• Perform urinalysis or urine microscopy to exclude urinary tract bleeding as a rare cause 1

Coeliac Disease Screening

• Screen for coeliac disease serologically (tissue transglutaminase antibody with IgA level) 1, 2
• Coeliac disease is found in 3-5% of IDA cases and represents a non-bleeding cause of iron deficiency 1
• This is critical because it affects absorption rather than causing blood loss 3

First-Line GI Investigation

Bidirectional Endoscopy

Perform both gastroscopy and colonoscopy as the standard first-line investigation in men with newly diagnosed IDA 1

Upper Endoscopy (Gastroscopy)

• Expected to reveal a cause in 30-50% of patients 1
• Obtain small bowel biopsies during gastroscopy even if mucosa appears normal, as 2-3% of IDA patients have coeliac disease 1
• Look for gastric cancer, peptic ulcer, angiodysplasia, and atrophic gastritis 1, 3

Lower Endoscopy (Colonoscopy)

• Perform colonoscopy even if upper endoscopy reveals a lesion (unless carcinoma or coeliac disease is found), as dual pathology occurs in 10-15% of patients 1
• Do not accept minor findings like oesophagitis, erosions, or peptic ulcer as the sole cause until the colon is examined 1
• If colonoscopy is not feasible, CT colonography is a reasonable alternative 1
• Colonoscopy is superior to barium enema as it demonstrates angiodysplasia and allows biopsy 1

Important Caveat

Do not perform faecal occult blood testing - it is insensitive and non-specific and adds no diagnostic value 1

If Initial Workup is Negative

When to Investigate Further

Further investigation of the small bowel and renal tract is indicated if: 1

• Inadequate response to iron replacement therapy (hemoglobin rise <10 g/L within 2 weeks) 1
• Recurrent IDA after initial correction 1
• Transfusion-dependent anemia 1

Small Bowel Investigation

• Capsule endoscopy is the preferred test for examining the small bowel, as it is highly sensitive for mucosal lesions 1
• CT or MRI enterography may be considered if capsule endoscopy is not suitable, and these are complementary for inflammatory and neoplastic disease 1
• Small bowel radiology is rarely useful unless Crohn's disease is suspected 1
• After negative capsule endoscopy of acceptable quality, further GI investigation is only needed if IDA persists despite iron replacement 1

Additional Considerations

• Enteroscopy may detect and treat small bowel angiodysplasia in transfusion-dependent cases 1
• Mesenteric angiography has limited use but may demonstrate vascular malformations in transfusion-dependent IDA 1

Non-Bleeding Causes to Consider

In 51% of cases, the cause may not be bleeding-related: 3

• Atrophic gastritis (most common non-bleeding cause) 3
• Helicobacter pylori gastritis 3
• Coeliac disease (already screened) 3
• Impaired absorption from previous gastric surgery 1, 4

Key Clinical Pitfalls

1. Do not defer iron replacement therapy while awaiting investigations (unless colonoscopy is imminent) 1
2. Do not stop investigating after finding minor upper GI lesions - always complete lower GI evaluation 1
3. Do not assume dietary deficiency is the sole cause - full investigation is still required 1
4. Do not rely on symptoms to guide investigation - they rarely correlate with findings 1