Mair R, Lee S, Plummer N, et al. - In advanced chronic kidney disease (CKD), greater reduction occurs in secretory clearances for many solutes relative to the reduction in GFR. Uremic symptoms in patients approaching dialysis may be attributable to impaired secretion of these solutes.

• Simultaneous urine and plasma samples from 16 CKD patients with an estimated GFR of 7±2 ml/min per 1.73 m² and 16 control participants were investigated for solutes using metabolomic analysis.

• In control participants, 39 secreted solutes with fractional clearance > 3.0 were identified.

• CKD patients showed reduced fractional clearance values on average to 65%±27% of those in controls.

• Advanced CKD cases show variable impairment of secretory clearances as indicated by assays of the secreted anions phenylacetylglutamine, p-cresol sulfate, indoxyl sulfate, and hippurate.

• Marked reduction in fractional clearances was noted for phenylacetylglutamine, p-cresol sulfate, and indoxyl sulfate, but not for hippurate.