Impact of Expanded Hemodialysis on Inflammation and Iron Metabolism in Chronic Hemodialysis Patients

Microinflammation and functional iron deficiency are major contributors to anemia and treatment burden in maintenance hemodialysis (HD). Medium cutoff (MCO) membranes enhance the removal of middle- and large-sized solutes implicated in these pathways, yet real-world data using routinely measured inflammatory and iron-related markers are scarce. This study examined the effects of MCO-based expanded HD on inflammatory indices, iron metabolism, and anemia-related treatment requirements. In this single-center retrospective study, 22 maintenance HD patients (11 who continued on high-flux dialyzers and 11 who were switched to MCO dialyzers) were followed for 24 weeks. Baseline and 24-week assessments included C-reactive protein (CRP), the CRP/albumin ratio, neutrophil count, and composite inflammatory indices, as well as serum iron, transferrin saturation (TSAT), total iron-binding capacity (TIBC), and ferritin. Monthly intravenous iron supplementation and weekly erythropoiesis-stimulating agent (ESA) doses were also documented. Baseline characteristics were comparable between groups. Over the 24-week period, the MCO group showed a significant decline in neutrophil count (p = 0.042) and downward trends in CRP and the CRP/albumin ratio, while both markers increased significantly in patients maintained on high-flux dialyzers. Serum albumin remained stable in all participants. Parallel to the improvement in inflammation, the MCO group demonstrated significant enhancements in iron-handling parameters, with higher serum iron (p = 0.008) and TSAT (p = 0.005), and lower TIBC (p = 0.007), none of which were observed in the high-flux group. Between-group Δ-differences were significant for CRP (p = 0.010), CRP/albumin ratio (p = 0.013), serum iron (p = 0.040), TIBC (p = 0.005), and TSAT (p = 0.005). Hemoglobin levels remained stable in both groups, while intravenous iron and ESA requirements showed modest within-group reductions in the MCO cohort. In this exploratory retrospective analysis, MCO membrane use was associated with favorable trends in inflammatory markers and iron-handling parameters, alongside modest within-group reductions in intravenous iron and ESA requirements, without compromising serum albumin. These findings suggest that MCO therapy may help mitigate microinflammation and support more efficient anemia management in real-world HD practice.