The Goal Achieving Neutral Phosphate Balance

Neutral phosphorus balance is achieved when total body phosphorus generation (GiP) is balanced by total body phosphorus elimination (JiP). Whole body iP generation is dependent on (i) intestinal iP and protein absorption and (ii) the amount of iP released from or deposited in endogenous tissues, such as bone. Phosphate binders (PBs) are used to decrease GiP by effectively lowering intestinal phosphorus absorption. In the face of lacking renal function, iP elimination in dialysis patients is almost completely dependent on dialytic iP removal. It is therefore clear that a neutral phosphorus balance can only be achieved when the total amount of iP, which has either been intestinally absorbed or released from endogenous tissues during the interdialytic phase, is completely removed by dialysis. Since phosphate removal during dialysis is limited, as delineated below, the only way to achieve neutral balance with current treatment strategies is to lower GiP to a minimum by optimizing the effects of PBs and inhibiting or preventing the release of phosphorus from endogenous tissues. The difference between iP generation and total iP removal is the quantity potentially deposited in tissues. In hemodialysis (HD) patients overall iP mass balance can be described as follows:


where: ATciP = phosphate accumulation in tissue compartments; G iP = phosphorus generation; Jd iP = dialyzer phosphorus removal; FiP = phosphorus content of ingested food; JbiP = phosphorus removal by PBs; ZiP = intestinal phosphorus absorption rate; RiP = phosphorus release from endogenous tissues, and DiP = phosphorus deposition in endogenous tissues.

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