Clinical aspects and overview of renal anaemia

Anaemia is an almost ubiquitous complication of chronic kidney disease, which has a number of implications for the patient. It is associated with adverse outcomes, an increased rate of red cell transfusions, poor quality of life, and reduced physical capacity. Severe anaemia also impacts on cardiac function, as well as on platelet function, the latter contributing to the bleeding diathesis of uraemia. Renal anaemia occurs mainly in the later stages of chronic kidney disease (stages 3B, 4, and 5), and up to 95% of patients on dialysis suffer from this condition. It is caused largely by inappropriately low erythropoietin levels, but other factors such as a shortened red cell survival also play a part. The anaemia is usually normochromic and normocytic, unless concomitant iron deficiency is present. The latter is also common in renal failure, partly due to low dietary iron intake and absorption, and partly due to increased iron losses. Prior to the 1990s, treatment options were limited, and many patients (particularly those on haemodialysis) required regular blood transfusions, resulting in iron overload and human leucocyte antigen sensitization. Correction of anaemia requires two main treatment strategies: increased stimulation of erythropoiesis, and maintenance of an adequate iron supply to the bone marrow. Ever since the introduction of recombinant human erythropoietin, it has been possible to boost erythropoietic activity, and both oral and intravenous iron products are available to provide supplemental iron. In dialysis patients, oral iron is usually poorly absorbed due to upregulation of hepcidin activity, and intravenous iron is often required. The physiological processes relevant to red cell production are described, as well as the prevalence, characteristics, pathogenesis, and physiological consequences of renal anaemia.