Large uremic toxins: an unsolved problem in end-stage kidney disease

Patients with end-stage kidney disease (ESKD) on maintenance hemodialysis are subject to a high burden of inflammation and cardiovascular disease, driven at least in part by retention of uremic solutes. Existing dialysis technologies using high-flux membranes offer limited clearance of solutes >15 kDa. New approaches to improve the removal of large uremic toxins include the novel medium cut-off dialysis membranes with pores larger than those in high-flux membranes. These new membranes provide the potential to improve the clearance of large middle molecules up to 50 kDa. In this review, we discuss 18 uremic toxins with molecular weights between 15 and 60 kDa that are retained in ESKD, for which there is evidence of a link to inflammation and/or cardiovascular disease. These include inflammatory proteins, cytokines, adipokines and other signaling proteins. Improved clearance of this group of difficult to remove molecules has the potential to lead to improved outcomes in dialysis patients by reducing the burden of cardiovascular disease, which now needs to be assessed in robust clinical trials.