Peritoneal phosphate removal varies by peritoneal dialysis regimen: an underestimated parameter of phosphate control.

Background: The optimization of phosphate (P) removal by peritoneal dialysis (PD) is often underestimated. Our objective was to investigate peritoneal P clearance and its relationship with standard adequacy targets, hyperphosphatemia and automated PD (APD) parameters.

Methods: Dialysis dose, P clearances (24-hour urine and effluent samples), estimated percentage of diffusive P removal and peritoneal transport rate (PET) were evaluated in 77 adult prevalent PD patients.

Results: Total P removal strongly correlated with residual renal function parameters, dissociated from peritoneal Kt/V urea (r=-0.36; p=0.02) and creatinine clearance (r=-0.32; p<0.0001). A correlation of P clearance with net ultrafiltration was not found. Among the variables studied, only renal and peritoneal P clearances were significantly lower in hyperphosphatemic patients. In APD, peritoneal phosphate clearance was positively correlated with 4-hour dialysate to plasma creatinine ratio (r=0.46; p=0.039). Slow transporters had higher peritoneal P clearances under continuous ambulatory PD (CAPD) regimens. Hyperphosphatemia was significantly associated with a lower number of APD cycles and shorter nightly therapy time, with insufficient dwell time individualization.

Conclusions: P peritoneal clearance is a modifiable parameter of P control in PD regimens and an additional adequacy target. Prescription skills are recommended in APD patients, particularly in anurics, to take into account peritoneal transport rate.