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Kidney Week

Abstract: PO0455

The Phosphate-to-Urinary Urea Nitrogen Ratio (P/UUN): A Tool to Evaluate Phosphate Intake and Excretion in CKD Patients

Session Information

Category: CKD (Non-Dialysis)

  • 2101 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

  • Pendon-Ruiz de Mier, Victoria, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Rodelo-Haad, Cristian, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Santamaria, Rafael, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • López baltanás, Rodrigo, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Membrives González, Cristina, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Munoz-Castaneda, Juan R., Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Martin-Malo, Alejandro, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Soriano, Sagrario, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
  • Rodriguez Portillo, Mariano, Instituto Maimonides de Investigacion Biomedica de Cordoba, Cordoba, Andalucía, Spain
Background

Phosphate (P) restriction is crucial in CKD patients. Classically, P intake has failed to correlate with 24-h phosphaturia. Organic or inorganic P have different intestinal absorption rates, which might explain the lack of correlation between P intake and phosphaturia. Thus, we aimed to evaluate if the source of dietary P rather than the total P ingested determines phosphaturia, and to what extent inorganic P intake modifies phosphaturia

Methods

A 3-day dietary survey was performed in 71 stages G2-3 CKD patients to estimate the amount and source of P intake. 24-h urine samples were collected. Total phosphaturia, the FeP(%), and P/UUN, which reflect intestinal absorption of P relative to proteins absorbed and metabolized), were evaluated. P/UUN ratio tertiles were contrasted with the other variables analyzed (T1<58.9mg/g,T2=58.9-71.1mg/g,T3>71.1mg/g). Statistics were performed using Rv3.6.2

Results

The P intake was 1086.5±361.3 mg/day. P intake was 64.0%,22.1%, and 14.1% from animal, vegetables, and inorganic sources respectively. Total P intake did not correlate with urinary P (p=0.12), nor FeP. Patients ingesting more P ingested more inorganic P (Fig1). P intake correlated with P/UUN ratio(p=0.008). Patients in the upper P/UUN tertile showed the highest daily P intake (p=0.04) from inorganic sources (p=0.03), and the highest phosphaturia (p=0.04)

Conclusion

P/UUN reflects the total P intake and provides information about the amount of inorganic P, and could be used to guide the appropriate nutritional advice for CKD patients.

Fig1 Correlation between P intake and the different sources. A. Animal, B. Vegetal, C. Inorganic