Peritoneal phosphate clearance is influenced by peritoneal dialysis modality, independent of peritoneal transport characteristics.

BACKGROUND AND OBJECTIVES Hyperphosphatemia is an independent risk factor for mortality in ESRD, but factors regulating phosphate clearance on peritoneal dialysis (PD) are incompletely understood. The objective of this study was to test the hypothesis that peritoneal phosphate clearance is better with continuous ambulatory PD (CAPD) as compared with continuous cyclic PD (CCPD) after adjusting for membrane transport status. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In this cross-sectional and retrospective study, measurements of peritoneal phosphate clearance of 129 prevalent PD patients were reviewed. Patients were divided according to membrane transport status (high, high average, low average-low categories) and PD modality (CAPD or CCPD). RESULTS Among high transporters, peritoneal phosphate clearances were comparable in both modalities. However, treatment with CAPD was associated with increased peritoneal phosphate clearance compared with CCPD among high-average transporters (42.4 +/- 11.4 versus 36.4 +/- 8.3 L/wk/1.73 m(2), P = 0.01), and low-average-low transporters (35.6 +/- 5.9 versus 28.9 +/- 11 L/wk/1.73 m(2), P = 0.034). On multivariate linear regression, PD modality, membrane transport category, and peritoneal creatinine clearance, but not Kt/V urea, were independently associated with peritoneal phosphate clearance. CONCLUSIONS Peritoneal phosphate clearance is determined by PD modality and membrane transport category, suggesting that PD regimes with longer dwell times may help control hyperphosphatemia in lower transporters.