How should a patient with iron deficiency anemia and impaired renal function be managed?

CBC Interpretation and Management of Iron Deficiency Anemia with Impaired Renal Function

Key Laboratory Findings

This patient has iron deficiency anemia with functional iron deficiency in the setting of chronic kidney disease (CKD) Stage 3, requiring immediate oral iron supplementation and investigation for underlying causes. 1

Anemia Profile

• Hemoglobin 10.5 g/dL (low) with Hematocrit 35.9% (low) confirms anemia 1
• MCV 97.3 fL (normal-high range) with MCH 28.5 pg (normal) and MCHC 29.2 g/dL (low) indicates hypochromic anemia despite normal MCV 2
• RDW 17.0% (elevated) reflects anisocytosis, consistent with iron deficiency 3

Iron Studies Pattern

• Ferritin 421.7 ng/mL (elevated) with Iron 30 ug/dL (low), TIBC 188 ug/dL (low), and Transferrin 129 mg/dL (low) indicates functional iron deficiency 1, 4
• This pattern shows adequate iron stores but insufficient iron availability for erythropoiesis, likely due to elevated hepcidin from CKD 4
• The elevated ferritin is an acute phase reactant and does not reflect true iron stores in CKD 1

Renal Function

• eGFR 59.15 mL/min/1.73 m² confirms CKD Stage 3 1
• BUN/Creatinine ratio 22.83 (elevated) suggests prerenal component or chronic kidney disease 1

Other Findings

• Monocytes 13.8% (elevated) may reflect chronic inflammation 4
• Lymphocytes (Absolute) 0.89 x10E3/uL (low) suggests mild lymphopenia 4
• Calcium 8.6 mg/dL (low) is consistent with CKD-related mineral bone disorder 1

Immediate Management Strategy

Iron Replacement Therapy

Start with oral iron supplementation as first-line therapy: ferrous sulfate 200 mg once daily, despite the presence of CKD. 1, 2

• In CKD Stage 3 (non-dialysis), oral iron remains appropriate initial therapy when TSAT would be calculated as approximately 16% (Iron 30/TIBC 188 × 100) 1, 4
• Do not defer iron therapy while awaiting investigations 1
• Add vitamin C 500 mg with iron to enhance absorption, particularly important given the functional iron deficiency 2

Alternative Oral Iron Strategies if Intolerance Develops

• Reduce to one tablet every other day if gastrointestinal side effects occur 1
• Consider alternative formulations (ferrous fumarate or ferrous gluconate) if intolerant to at least two preparations 1

When to Consider Intravenous Iron

Intravenous iron should be considered if: 1

• Intolerance to at least two different oral iron preparations develops 1
• No hemoglobin response after 4 weeks of adequate oral therapy 1
• Hemoglobin fails to rise by 2 g/dL after 3-4 weeks 1

For CKD patients specifically, IV iron is preferred when: 1, 4

• TSAT remains <20% despite oral iron therapy 1
• Functional iron deficiency persists (which this patient has) 4
• Rapid correction is needed 5

Monitoring Protocol

Check hemoglobin response at 4 weeks: 1

• Expected rise of 2 g/dL after 3-4 weeks indicates adequate response 1
• If no response, consider IV iron or investigate for continued blood loss, malabsorption, or non-compliance 1

Continue oral iron for 3 months after hemoglobin normalization to replenish iron stores 1, 2

Monitor iron parameters every 3 months once stable 1

Investigation for Underlying Cause

This patient requires gastrointestinal investigation given the iron deficiency anemia: 1

Age-Based Investigation Strategy

• If patient >45 years: Perform both upper endoscopy with small bowel biopsy AND colonoscopy (or barium enema) 1
• If patient <45 years: Perform upper endoscopy only if upper GI symptoms present; check antiendomysial antibodies (with IgA level) to exclude celiac disease 1

Additional Considerations

• Assess for menstrual blood loss if premenopausal woman 2
• Evaluate for chronic blood loss from GI tract, which is common with CKD 1
• Consider malabsorption if poor response to oral iron 1

Special Considerations for CKD

Functional iron deficiency is common in CKD and requires different management than absolute iron deficiency: 1, 4

• The elevated ferritin (421.7 ng/mL) does not exclude iron deficiency in CKD patients 4
• In CKD, absolute iron deficiency is defined as TSAT ≤20% and ferritin ≤100 ng/mL (predialysis patients) 4
• This patient has functional iron deficiency: low TSAT with elevated ferritin 4
• Reference to nephrology guidelines is recommended for ongoing management of CKD-associated anemia 1

CKD-Specific Iron Targets

• Target TSAT >20% and ferritin 100-500 ng/mL for non-dialysis CKD patients 1, 4
• More aggressive iron repletion may benefit cardiovascular outcomes in CKD 5

Common Pitfalls to Avoid

• Do not assume elevated ferritin excludes iron deficiency in CKD - it is an acute phase reactant 4
• Do not defer iron therapy while awaiting endoscopy unless colonoscopy is imminent 1
• Do not use oral iron alone in dialysis patients - they require IV iron 1
• Do not overlook the low calcium - address CKD-mineral bone disorder 1
• Do not stop iron after hemoglobin normalizes - continue for 3 months to replenish stores 1

Risk Stratification

This patient has multiple risk factors for poor outcomes: 1

• CKD Stage 3 with declining renal function 1
• Functional iron deficiency limiting erythropoiesis 4
• Anemia (Hgb 10.5 g/dL) associated with increased morbidity and mortality in CKD 4
• Low calcium suggesting CKD-mineral bone disorder 1

Careful monitoring and aggressive iron repletion are essential to prevent progression and improve quality of life. 1, 5