Tissue sodium stores in peritoneal dialysis and hemodialysis patients determined by sodium-23 magnetic resonance imaging

Abstract

Background. Tissue sodium (Na+) content in patients on maintenance hemodialysis (MHD) and peritoneal dialysis (PD) was previously explored using 23Na+ magnetic resonance imaging (23NaMRI). Larger studies would provide a better understanding of Na+ stores in patients on dialysis as well as the factors influencing this Na+ accumulation. Methods. In this cross-sectional study, we quantified the calf muscle and skin Na+ content in 162 subjects (10 PD, 33 MHD patients and 119 controls) using 23NaMRI. Plasma levels of interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) were measured to assess systemic inflammation. Sixty-four subjects had repeat 23NaMRI scans that were analyzed to assess the repeatability of the 23NaMRI measurements. Results. Patients on MHD and PD exhibited significantly higher muscle and skin Na+ accumulation compared with controls. African American patients on dialysis exhibited greater muscle and skin Na+ content compared with non–African Americans. Multivariable analysis showed that older age was associated with both higher muscle and skin Na+ and male sex was associated with increased skin Na+ deposition. Greater ultrafiltration was associated with lower skin Na+ in patients on PD (Spearman’s q = ̄0.68, P = 0.035). Higher plasma IL-6 and hsCRP levels correlated with increased muscle and skin Na+ content in the overall study population. Patients with higher baseline tissue Na+ content exhibited greater variability in tissue Na+ stores on repeat measurements. Conclusions. Our findings highlight greater muscle and skin Na+ content in dialysis patients compared with controls without kidney disease. Tissue Na+ deposition and systemic inflammation seen in dialysis patients might influence one another bidirectionally.