Should the patient be referred to hematology or gastroenterology for iron infusion?

Referral for Iron Infusion: Gastroenterology vs Hematology

For most adults with iron deficiency anemia requiring intravenous iron infusion, refer to gastroenterology, as approximately one-third of men and postmenopausal women have underlying GI pathology that requires investigation and management. 1

Primary Recommendation

The British Society of Gastroenterology 2021 guidelines make clear that IDA in adults without obvious explanation warrants urgent GI investigation because GI malignancies and other significant GI pathologies commonly present this way 1. Since gastroenterologists will need to investigate the underlying cause through bidirectional endoscopy, they are best positioned to also manage the iron replacement therapy.

When to Refer to Gastroenterology

Refer to gastroenterology for:

• Men and postmenopausal women with new IDA without obvious non-GI cause
• Patients with suspected or confirmed GI blood loss (portal hypertensive gastropathy, angiodysplasia, inflammatory bowel disease)
• Any patient requiring investigation of the GI tract to identify the source of iron deficiency
• Inflammatory bowel disease patients with iron deficiency 1

The evidence shows gastroenterology day hospitals frequently administer IV iron, with portal hypertensive gastropathy, IBD, and intestinal angiodysplasia being the most common indications 2.

When to Refer to Hematology (or Nephrology/Cardiology)

Refer to hematology or specialty-specific services for:

• Chronic kidney disease (GFR <60 mL/min/1.73m²): Nephrology should manage iron replacement, as interpretation of iron studies differs in CKD (ferritin ≤100-200 μg/L depending on dialysis status) 1

• Chronic heart failure: Cardiology should manage, as IV iron (not oral) shows prognostic benefit even with functional iron deficiency (ferritin <100 μg/L or transferrin saturation <20%) 1

• Hematologic disorders: When there's suspicion of bone marrow pathology, hemolysis, or other non-GI hematologic causes

Critical Pitfalls to Avoid

Do not refer for small bowel evaluation without completing basic workup first 3. A 2017 study found 77.9% of patients referred for small bowel investigation had incomplete pre-referral studies. Before any referral, ensure:

• Upper endoscopy with H. pylori testing (completed in only 58.3% of referred patients)
• Quality colonoscopy (recent, complete, adequate preparation)
• Celiac disease screening (done in only 24.7% of referred patients)

Practical Algorithm

1. Confirm iron deficiency: Ferritin is the single best marker; TSAT <20% indicates deficiency 1

2. Identify the clinical context:

   • GI symptoms/suspected GI pathology → Gastroenterology
   • CKD (GFR <30) → Nephrology
   • Heart failure with reduced EF → Cardiology
   • No clear cause after basic workup → Gastroenterology (for investigation)

3. Complete pre-referral workup to avoid delays and inappropriate referrals

4. Consider co-management: Patients with CKD or heart failure may still need GI investigation if they have confirmed absolute iron deficiency, ideally coordinated between specialties 1

The key principle is that gastroenterology should be the default referral for most adult IDA cases requiring IV iron, as they can simultaneously investigate the underlying cause and provide treatment, improving both diagnostic yield and patient outcomes.