Table 2.

Residual kidney and peritoneal dialysis solute clearance (n=29)

SolutesMolecular Weight, g/molProtein Binding, %aClearance, ml/min per 1.73 m2Ratios
KidneyPeritonealKidney to Peritoneal ClearanceKidney Solute Clearance to GFRurea+CrPeritoneal Solute Clearance to Peritonealurea+Cr Clearance
Filtration
 Urea609.0 [6.8 to 11.2]8.4 [7.3 to 9.4]1.2 [0.9 to 1.6]
 Creatinine1138.2 [6.3 to 10.2]2.8 [2.3 to 3.2]3.7 [2.6 to 4.9]
Secretion
 Cinnamoylglycine20594.99.5 [6.7 to 12.2]0.5 [0.3 to 0.6]22.4 [7.2 to 55.6]1.2 [1.0 to 1.4]0.08 [0.06 to 0.10]
 Dimethyluric acid19663.657.2 [31.7 to 82.7]3.4 [2.4 to 4.4]17.4 [4.3 to 28.6]7.7 [3.2 to 12.2]0.59 [0.4 to 0.7]
 Hippurate17965.794.6 [67.3 to 121.9]8.8 [5.2 to 12.3]15.6 [5.1 to 30.2]13.7 [10.0 to 17.3]1.5 [1.0 to 1.9]
 Indoxyl sulfate21392.96.6 [5.0 to 8.2]1.0 [0.5 to 1.5]9.9 [3.3 to 19.9]1.03 [0.7 to 1.3]0.2 [0.1 to 0.2]
 Isovalerylglycine159ND29.3 [21.1 to 37.6]3.8 [3.1 to 4.5]8.4 [2.4 to 13.3]3.6 [3.2 to 4.1]0.7 [0.6 to 0.7]
 Kynurenic acid1899718.7 [14.0 to 23.4]0.9 [0.6 to 1.1]23.0 [7.8 to 42.9]2.6 [2.1 to 3.1]0.2 [0.1 to 0.2]
 p-cresol sulfate18888.51.3 [1.0 to 1.6]0.3 [0.2 to 0.4]5.4 [1.7 to 9.5]0.2 [0.1 to 0.2]0.05 [0.04 to 0.06]
 Pyridoxic acid18380.248.7 [34.3 to 63.2]4.0 [2.8 to 5.2]12.9 [3.8 to 22.2]6.0 [4.9 to 7.1]0.7 [0.5 to 0.9]
 Tiglylglycine15718.321.5 [14.8 to 28.3]2.1 [1.5 to 2.6]10.8 [3.5 to 16.3]2.7 [2.2 to 3.1]0.3 [0.3 to 0.4]
 Xanthosine28429.59.1 [5.8 to 12.3]1.6 [1.2 to 1.9]6.3 [2.2 to 14.8]1.2 [0.9 to 1.4]0.3 [0.2 to 0.3]
  • Values are expressed as mean [95% confidence interval]. ND, protein binding not detected; MWCO, molecular weight cut-off.

  • a To evaluate the extent of protein binding, we performed ultrafiltration experiments. Briefly, plasma was filtered using a centrifugal filter (Amicon Ultra; 3-kD MWCO) at 11,200×g for 30 min at room temperature. The concentration of solutes in the filtrate was then determined using the same method as for plasma and compared with the concentration of solutes in unfiltered plasma. The proportion of the solutes in the filtrate was assumed to be unbound in plasma. Preliminary experiments were performed to confirm that observed differences between the filtrate and unfiltered plasma could not be attributed to adsorption to the Amicon Ultra filtration units (data not shown).