 The investigators therefore propose to use novel Na MRI imaging to examine the Na deposition in skin, muscle and skeleton of three groups of patients: 1 chronic 3-times-a-week in-center hemodialysis patients, 2 peritoneal dialysis patients, and 3 patients with CKD stage 4-5; and compare these results to age and sex matched healthy controls. Additionally, they intend to investigate the association between sodium deposition in these tissues with uremic symptomatology and biochemical markers of metabolism. 