Phenols are uremic toxins of intestinal origin formed by bacteria during protein metabolism. Of these molecules, p-cresol is the most studied and has been associated with renal function impairment and vascular damage. Bisphenol A (BPA) is a molecule with structural similarity with phenols found in plastic food and beverage containers as well as in some dialyzers. BPA is considered an environmental toxicant based on animal and cell culture studies. Japanese authorities recently banned BPA use in baby bottles based on observational association studies in newborns. BPA is excreted in urine and uremic patients present higher serum levels, but there is insufficient evidence to set cut-off levels or to link BPA to any harmful effect in CKD. However, the renal elimination and potential exposure during dialysis warrant the monitoring of BPA exposure and the design of observational studies in which the potential health risks of BPA for end-stage renal disease patients are evaluated. 1. Uremic Toxins Multiple molecules accumulate in chronic kidney disease (CKD), are responsible for uremic symptoms, and contribute to increased mortality (uremic toxins). Removal of uremic toxins therefore is accompanied by an improvement in the clinical situation. The term of uremic toxin was created by Piorry in 1847 to indicate the “blood contamination with urine” to refer to the signs and symptoms resulting from kidney disease that increase mortality. Bergstrom [1] proposed that a uremic toxin should be defined as one molecule that meets the following premises:(1)the chemical identity and concentration in biological fluids should be known,(2)the concentration in uremic individuals should be higher than in nonuremic subjects,(3)the concentration should correlate with uremic symptoms, and symptoms should disappear by decreasing the concentration. Uremic toxins have been classified according to size [2]. Over 350 small uremic toxins have been described with a molecular weight below 500？Da [3]. Medium-sized molecules have a molecular weight between 500 and 5000？Da. Many uremic toxins are bound to proteins which hamper their clearance. Uremic toxins are responsible for uremic disease. Among the changes that have been directly related to uremic toxins we find progressive loss of renal function, cardiovascular morbidity, and uremic symptoms such as anorexia, vomiting, weakness, sleep disturbances, and neuropathy. The origin of uremic toxins is multiple. Most uremic toxins originate from the endogenous cellular metabolism. However, there is a growing list of uremic toxins originated in
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