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Fractional excretion of phosphorus and vascular calcification in stage 3 chronic kidney disease
  1. Manuel Jiménez Villodres1,
  2. Guillermo García Gutiérrez2,
  3. Patricia García Frías1,
  4. José Rioja Villodres3,
  5. Mónica Martín Velázquez1,
  6. Miguel Ángel Sánchez Chaparro4,5,
  7. Carmen Pérez López4,
  8. Pedro Valdivielso4,5
  1. 1Nephrology Unit, Hospital Virgen de la Victoria, Málaga, Spain
  2. 2Radiology Unit, Hospital Virgen de la Victoria, Málaga, Spain
  3. 3Instituto de Investigación Biomédica de Málaga (IBIMA), University of Málaga, Málaga, Spain
  4. 4Internal Medicine Unit, Hospital Virgen de la Victoria, Málaga, Spain
  5. 5Department of Medicine and Dermatology, Instituto de Investigación Biomédica de Málaga (IBIMA), University of Málaga, Málaga, Spain
  1. Correspondence to Dr Miguel Ángel Sánchez Chaparro, Department of Internal Medicine and Dermatology, University of Málaga, Málaga 29016, Spain; masch{at}uma.es

Abstract

The role of renal excretion of Pi in relation to vascular calcification (VC) in patients in the early stages of chronic kidney disease (CKD) is controversial. Thus, we determine the relation between fractional excretion of phosphorus (FEP) and VC, measured using two methods in a cross-sectional study of patients with stage 3 CKD. We recorded demographic data, anthropometry, comorbidities and active treatment. We measured 24-hour urine FEP and, in serum, measured fibroblast growth factor 23 (FGF23), α-Klotho, intact parathyroid hormone (iPTH), calcium and phosphorus. VC was measured by lateral abdominal radiography (Kauppila index (KI)) and CT of the abdominal aorta (measured in Agatston units). In 57% of subjects, abnormal VC was present when measured using CT, and in only 17% using lateral abdominal radiography. Factors associated with VC using CT were age, cardiovascular risk factors, vascular comorbidity, microalbuminuria and levels of FGF23, phosphorus and calcium x phosphorus product (CaxP); although only age (OR 1.25, 95% CI 1.11 to 1.41), smoking (OR 21.2, CI 4.4 to 100) and CaxP (OR 1.21, CI 1.06 to 1.37) maintained the association in a multivariate analysis. By contrast, only age (OR 1.35, 95% CI 1.07 to 1.74), CaxP (OR 1.14, CI 1.13 to 1.92) and FEP (OR 1.07,95% CI 1004 to 1.14) were associated with abnormal VC in the lateral abdominal radiography. In conclusion, in patients with stage 3 CKD, the detection of VC by abdominal CT is more sensitive than conventional X-rays. Moreover, CaxP is associated with cardiovascular risk factors and vascular comorbidity; quantification of FEPi in these patients provides additional clinical information in advanced VC detected by KI.

  • fractional excretion of phosphorus
  • FGF23
  • alpha-Klotho
  • vascular calcification
  • stage 3 CKD

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Footnotes

  • Contributors MJV selected patients, review data, interpreted data, designed the project and gave final approval of the version to be published. GGG measured vascular calcification, interpreted data and gave final approval of the version to be published. PGF managed patients, interpreted data and gave final approval of the version to be published. JRV performed biochemical analyses, review data and gave final approval of the version to be published. MMV managed patients, interpreted data, review data and gave final approval of the version to be published. MÁSC performed statistical analyses, providing intellectual content of critical importance and gave final approval of the manuscript. CPL managed patients, interpreted data, review critically the manuscript and gave final approval of the version to be published. PV designed project, interpreted data and drafted the manuscript.

  • Funding This study has been financed with the help of the CTS-159 group of the Plan Andaluz de Innovación e Investigación (Andalusian Plan for Research and Innovation) (PAIDI).

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval Comité de Ética e Investigación de Málaga, Spain.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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