Dietary and pharmacological control of calcium and phosphate metabolism in predialysis stages of chronic kidney disease.

Data on calcium and phosphate metabolism in the predialysis stages of chronic kidney disease (CKD) are scarce when compared with the available information on patients on dialysis. Visible derangements of calcium and phosphate levels start to become apparent when GFR falls below 40 ml/min. In some but not all patients, hyperphosphatemia may be a mortality risk predictor in CKD stages 4-5. There are only few treatment studies targeting hyperphosphatemia in these CKD stages. However, the RIND study, evaluating progression of coronary artery calcification in incident hemodialysis patients, demonstrated that vascular calcification processes manifest in predialysis stages in the majority of patients, which may well be linked to deranged calcium and phosphate homeostasis. Novel insights into the pathophysiology of calcium and phosphate handling, especially the discovery of the phosphatonin FGF23, suggest that a more complex assessment of phosphate balance is warranted. This assessment should include measurements of fractional phosphate excretion and phosphatonin levels to objectively judge and effectively correct phosphate overload. Copyright (c) 2009 S. Karger AG, Basel.