title: Increased serum phosphate concentrations in patients with advanced chronic kidney disease treated with diuretics.
abstract: BACKGROUND
  Serum phosphate concentrations usually show great variability in patients with advanced chronic kidney disease (ACKD) not on dialysis. Diuretics treatment can have an influence over the severity of mineral-bone metabolism alterations related to ACKD, but their effect on serum phosphate levels is less known.
  
  
  OBJECTIVE
  This study aims to determine whether diuretics are independently associated with serum phosphate levels, and to investigate the mechanisms by which diuretics may affect phosphate metabolism.
  
  
  METHODS
  429 Caucasian patients with CKD not on dialysis were included in this cross-sectional study. 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), and fractional excretion of phosphate (FEP).
  
  
  RESULTS
  58% of patients were on treatment with diuretics. Patients on diuretics showed significantly higher mean serum phosphate concentration (4.78 ± 1.23 vs. 4.24 ± 1.04 mg/dl; P<.0001), and higher TmP per GFR (2.77 ± 0.72 vs. 2.43 ± 0.78 mg/dl; P<.0001) than those not treated with diuretics. By multivariate linear and logistic regression, significant associations between diuretics and serum phosphate concentrations or hyperphosphataemia remained after adjustment for potential confounding variables. In patients with the highest phosphate load adjusted to kidney function, those treated with diuretics showed significantly lower FEP than those untreated with diuretics.
  
  
  CONCLUSIONS
  Treatment with diuretics is associated with increased serum phosphate concentrations in patients with ACKD. Diuretics may indirectly interfere with the maximum renal compensatory capacity to excrete phosphate. Diuretics should be considered in the studies linking the relationship between serum phosphate concentrations and cardiovascular alterations in patients with CKD.
authors.affiliation: Servicio de Nefrología, Hospital Infanta Cristina, Badajoz, Spain. fcaravacam@senefro.org
authors.forename: Francisco
authors.initials: F
authors.lastname: Caravaca
authors.forename: Guadalupe
authors.initials: G
authors.lastname: García-Pino
authors.forename: Rocío
authors.initials: R
authors.lastname: Martínez-Gallardo
authors.forename: Flavio
authors.initials: F
authors.lastname: Ferreira-Morong
authors.forename: Enrique
authors.initials: E
authors.lastname: Luna
authors.forename: Raúl
authors.initials: R
authors.lastname: Alvarado
authors.forename: Enrique
authors.initials: E
authors.lastname: Ruiz-Donoso
authors.forename: Edgar
authors.initials: E
authors.lastname: Chávez
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004232:Diuretics / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D010710:Phosphates / Q000097:blood*; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000188:drug therapy*
chemical_list: D004232:Diuretics; D010710:Phosphates