However, the failure of randomized trials to find a benefit of higher hemoglobin concentrations suggests that the anemiaoutcome association may be confounded by unknown factors.
2–5 The cause of anemia in CKD is multifactorial. A low hemoglobin concentration may result from reduced red
blood cell volume (true anemia) and/or from an increased extracellular water (ECW) volume (hemodilution) (Figure 1).6–8 Our recent study has shown that ECW volume overload is a common issue in non-dialysis-dependent CKD (ND-CKD) patients.9 However,
the prevalence of hemodilution in CKD is unclear, and its clinical impact has not been elucidated.