p-cresol sulfate and indoxyl sulfate: some clouds are gathering in the uremic toxin sky.

An increasing body of experimental and clinical evidence suggests that p-cresol sulfate and indoxyl sulfate contribute to the high cardiovascular burden in patients with chronic kidney disease. In a post hoc analysis on the HEMO trial, Shafi et al. failed to confirm an association between total p-cresol sulfate and indoxyl sulfate and cardiovascular outcomes in dialysis patients. Analytical issues and case-mix may explain the discrepant findings.