The Evolving Patterns of Uremia: Unmet Clinical Needs in Dialysis.

End-stage renal disease (ESRD) has become a challenging health problem worldwide. Currently, ESRD patients treated with hemodialysis mainly undergo low-flux hemodialysis, high-flux hemodialysis (HF-HD), or hemodiafiltration (HDF). The clearance of middle and large molecules is, however, quite insufficient as regards HF-HD, HDF, and on-line HDF. An unsatisfactory prognosis has led to improved dialysis technology and materials; both protein-leaking membranes and high cut-off membranes increase the clearance of uremic toxin, but in clinical application they may induce albumin loss. Novel membranes with similar clearance efficiency but little impact on albumin leakage are yet to be developed. To enhance the removal of uremic toxins and increase membrane permeability, a high retention onset (HRO) membrane with larger pore size and HRO, once defined as medium cut-off, has been developed in the past few years. Such a membrane enables leakage of larger size molecules including albumin. The dialysis using HRO membranes has recently been proposed as expanded hemodialysis (HDx). Theoretically, HDx could promote the removal of more toxin solutes retained in the blood of ESRD patients, and improve the outcomes of dialysis. However, randomized controlled trials are required to evaluate the long-term efficacy, safety, and side effects of HDx in the future.