Phosphate control in dialysis

Adamasco Cupisti,¹ Maurizio Gallieni,² Maria Antonietta Rizzo,² Stefania Caria,³ Mario Meola,⁴ Piergiorgio Bolasco<sup>3

1</sup>Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy; ²Nephrology and Dialysis Unit, San Carlo Borromeo Hospital, Milan, Italy; ³Territorial Department of Nephrology and Dialysis, ASL Cagliari, Italy; ⁴Sant'Anna School of Advanced Studies, University of Pisa, Pisa, Italy

Abstract: Prevention and correction of hyperphosphatemia is a major goal of chronic kidney disease–mineral and bone disorder (CKD–MBD) management, achievable through avoidance of a positive phosphate balance. To this aim, optimal dialysis removal, careful use of phosphate binders, and dietary phosphate control are needed to optimize the control of phosphate balance in well-nourished patients on a standard three-times-a-week hemodialysis schedule. Using a mixed diffusive–convective hemodialysis tecniques, and increasing the number and/or the duration of dialysis tecniques are all measures able to enhance phosphorus (P) mass removal through dialysis. However, dialytic removal does not equal the high P intake linked to the high dietary protein requirement of dialysis patients; hence, the use of intestinal P binders is mandatory to reduce P net intestinal absorption. Unfortunately, even a large dose of P binders is able to bind approximately 200–300 mg of P on a daily basis, so it is evident that their efficacy is limited in the case of an uncontrolled dietary P load. Hence, limitation of dietary P intake is needed to reach the goal of neutral phosphate balance in dialysis, coupled to an adequate protein intake. To this aim, patients should be informed and educated to avoid foods that are naturally rich in phosphate and also processed food with P-containing preservatives. In addition, patients should preferentially choose food with a low P-to-protein ratio. For example, patients could choose egg white or protein from a vegetable source. Finally, boiling should be the preferred cooking procedure, because it induces food demineralization, including phosphate loss. The integrated approach outlined in this article should be actively adapted as a therapeutic alliance by clinicians, dieticians, and patients for an effective control of phosphate balance in dialysis patients.

Keywords: phosphorus, hyperphosphatemia, dialysis, phosphate binders, diet, food preservatives