[Uremic Toxins: how can we improve the removal today?].

Uremic status results from a malfunctioning of kidneys due to the accumulation of compounds which, under normal conditions, are excreted or metabolized by the kidneys. If these compounds are biologically active, they are called uremic toxins. Such compounds have toxic effects on the cardio-vascular system. An useful classification, published by the European Uremic Toxin Work Group (EUTox) is: 1) small water-soluble compounds; 2) protein-bound compounds; 3) the larger "middle molecules". High-flux membranes and more efficient treatment techniques, like HDF, improve the removal of uremic toxins in the middle molecular-weight range, and recent studies suggest that these strategies have better results on the morbidity and mortality. Today new membranes, medium cut-off membranes (MCO), with increased pore size, allow for the removal of higher molecular-weight toxins, such as kappa and lambda light chains and/or mediators of inflammation. For toxins in the 15 to 45 KD-size range, MCO membranes improve the removal in comparison with high-flux HD and/or HDF. Therefore MCO membrane simplifies the treatment of HD patients with a removal spectrum that extend the current possibilities of the best available therapies for End Stage Renal Disease.