Prominent Accumulation in Hemodialysis Patients of Solutes... : Journal of the American Society of Nephrology (original) (raw)

Clinical Research

Prominent Accumulation in Hemodialysis Patients of Solutes Normally Cleared by Tubular Secretion

Sirich, Tammy L.*; Funk, Benjamin A.*; Plummer, Natalie S.*; Hostetter, Thomas H.†; Meyer, Timothy W.*

*Department of Medicine, Veterans Affairs Palo Alto Healthcare System and Stanford University, Palo Alto, California; and

†Department of Medicine, Case Western Reserve University, Cleveland, Ohio

Correspondence: Dr. Tammy L. Sirich, Nephrology 111R, Palo Alto VAHCS, 3801 Miranda Avenue, Palo Alto, CA 94303. Email: [email protected]

Received June 10, 2013

Accepted September 2, 2013

Abstract

Dialytic clearance of urea is efficient, but other small solutes normally secreted by the kidney may be cleared less efficiently. This study tested whether the high concentrations of these solutes in hemodialysis patients reflect a failure of passive diffusion methods to duplicate the efficacy of clearance by tubular secretion. We compared the plasma concentrations and clearance rates of four solutes normally cleared by tubular secretion with the plasma concentrations and clearance rates of urea and creatinine in patients receiving maintenance hemodialysis and normal subjects. The predialysis concentrations (relative to normal subjects) of unbound phenylacetylglutamine (122-fold), hippurate (108-fold), indoxyl sulfate (116-fold), and p-cresol sulfate (41-fold) were much greater than the concentrations of urea (5-fold) and creatinine (13-fold). The dialytic clearance rates (relative to normal subjects) of unbound phenylacetylglutamine (0.37-fold), hippurate (0.16-fold), indoxyl sulfate (0.21-fold), and p-cresol sulfate (0.39-fold) were much lower than the rates of urea (4.2-fold) and creatinine (1.3-fold). Mathematical modeling showed that prominent accumulation of the normally secreted solutes in hemodialysis patients could be accounted for by lower dialytic clearance relative to physiologic clearance combined with the intermittency of treatment. Whether or not more efficient removal of normally secreted solutes improves outcomes in dialysis patients remains to be tested.