Anemia and Renal Disease: The Overlooked Connection

Anemia and kidney disease are two medical conditions that frequently coexist, yet their connection is often under-recognized. Anemia, broadly defined as a reduction in the oxygen-carrying capacity of the blood due to decreased hemoglobin or red blood cell levels, is a common complication of chronic kidney disease (CKD). To fully appreciate this relationship, it is essential to understand both conditions independently and how they intersect in clinical practice.

Anemia can stem from a variety of causes, including iron deficiency, chronic inflammation, blood loss, and bone marrow suppression. In the general population, it is most often associated with nutritional deficiencies or chronic diseases. In the context of kidney disease, however, anemia takes on a more complex pathophysiology. The kidneys are vital organs that, among other roles, produce erythropoietin—a hormone responsible for stimulating the bone marrow to produce red blood cells. When kidney function begins to decline, as seen in CKD, erythropoietin production diminishes, leading to a decreased red blood cell count.

Chronic kidney disease is classified into five stages based on the estimated glomerular filtration rate (eGFR), which reflects the kidneys' ability to filter waste and excess fluids from the blood. As CKD progresses from early to advanced stages, the risk and severity of anemia increase. In fact, anemia is rarely seen in early-stage CKD but becomes significantly more prevalent in stages 3 to 5. This pattern underscores the strong correlation between declining kidney function and the onset of anemia.