From the Guidelines
Renal causes of microcytic anemia primarily include chronic kidney disease (CKD) with iron deficiency, which is a major contributor to the development of microcytic anemia in these patients. In CKD patients, several mechanisms contribute to microcytic anemia, including reduced erythropoietin production by damaged kidneys, impaired iron absorption due to elevated hepcidin levels, increased blood loss from uremic platelet dysfunction, and nutritional deficiencies 1. Iron deficiency is particularly common in these patients, especially those on hemodialysis who lose blood during treatments. According to the British Society of Gastroenterology guidelines, assessment of iron deficiency in CKD can be difficult, and measurement of ferritin and transferrin saturation may be helpful, but the interpretation of results is not the same as in patients who do not have CKD 1.
Key Mechanisms
- Reduced erythropoietin production by damaged kidneys
- Impaired iron absorption due to elevated hepcidin levels
- Increased blood loss from uremic platelet dysfunction
- Nutritional deficiencies
Management
- Iron supplementation (oral ferrous sulfate 325mg daily or IV iron such as ferric gluconate 125mg per dialysis session)
- Erythropoiesis-stimulating agents like epoetin alfa (50-100 units/kg three times weekly) when hemoglobin falls below 10 g/dL
- Regular monitoring of iron studies, including ferritin and transferrin saturation, is essential for proper management of anemia in renal patients 1.
Important Considerations
- Patients with CKD may also have GI pathology underlying their confirmed iron deficiency, and the decision about the need for endoscopic evaluation of the upper and lower GI tract in CKD should be made in conjunction with a nephrologist 1.
- Treatment of iron deficiency in CKD is usually initiated and monitored by the nephrology team, and may involve oral iron replacement, intravenous iron replacement therapy (IV IRT), or other treatments for anemia such as erythropoietin 1.
From the Research
Renal Causes of Microcytic Anemia
The renal causes of microcytic anemia can be attributed to several factors, including:
- Inadequate renal production of erythropoietin, which leads to decreased stimulation of the bone marrow to produce red blood cells (RBCs) 2
- Iron deficiency, which can be absolute or functional, and is often seen in patients with chronic kidney disease (CKD) 3, 4, 5, 6
- Iron dysregulation, which can affect erythropoiesis and lead to anemia, as well as cardiovascular disease and mortality 4
- Reduced iron absorption, occult blood loss, and impaired iron mobilization, which can contribute to iron deficiency and anemia 6
Pathophysiology of Anemia in CKD
The pathophysiology of anemia in CKD is complex and involves multiple mechanisms, including:
- Decrease in endogenous erythropoietin production 2, 5
- Absolute and/or functional iron deficiency 3, 4, 5, 6
- Inflammation with increased hepcidin levels, which can lead to iron sequestration and reduced iron availability 5
Diagnosis and Treatment of Anemia in CKD
The diagnosis of anemia in CKD involves estimating glomerular filtration rate (GFR) and checking hemoglobin levels 2. Treatment typically involves erythropoiesis-stimulating agents (ESAs) and iron supplements, either oral or intravenous 3, 2, 5, 6. However, iron administration should be approached with caution in patients with iron dysregulation, and treatment targets may need to be adjusted based on individual patient needs 4, 5.