Resumo

CARAVACA, Francisco et al. Increased serum phosphate concentrations in patients with advanced chronic kidney disease treated with diuretics. Nefrología (Madr.) [online]. 2013, vol.33, n.4, pp.486-494. ISSN 1989-2284.  https://dx.doi.org/10.3265/Nefrologia.pre2013.Feb.11872.

Background: Serum phosphate concentrations usually show great variability in patients with advanced chronic kidney disease (CKD) not requiring dialysis. Diuretics can alter mineral metabolism, and according to previous clinical observations, they may increase serum phosphate levels. Objectives: This study aims to confirm whether diuretics are independently associated with increased serum phosphate concentrations, and to investigate by which mechanisms diuretics may affect phosphate metabolism. Methods: In this cross-sectional, singlecentre study, 429 Caucasian patients with advanced CKD not on dialysis were included. In addition to conventional serum biochemical measures, the following parameters of renal phosphate excretion were assessed: 24 hours urinary phosphate excretion, tubular maximum phosphate reabsorption (TmP) per GFR, and fractional excretion of phosphate (FEP). Results: Fiftyeight percent of patients were on diuretics. Patients on diuretics showed significantly higher mean serum phosphate concentration (4.78±1.23 vs. 4.24±1.04mg/dl; p<.0001), and higher TmP per GFR (2.77±0.72 vs. 2.43±0.78mg/dl; p<.0001) than those of patients untreated with diuretics. By multivariate linear and logistic regression, significant associations between diuretics and serum phosphate concentrations or hyperphosphatemia remained after adjustment for potential confounding variables. In patients with the highest phosphate load weighted to kidney function, those treated with diuretics showed significantly lower FEP than that of patients untreated with diuretics. Conclusions: Diuretic treatment is associated with increased serum phosphate concentrations in patients with advanced CKD. Diuretics may indirectly interfere with the maximum renal compensatory capacity to excrete phosphate. Diuretics should be considered potential confounders in the relationship between serum phosphate concentrations and cardiovascular outcomes in patients with CKD.

Palavras-chave : Diuretics; Fractional phosphorous excretion; Hyperphosphataemia; Chronic kidney disease.

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