Usefulness of urinary parameters in advanced chronic kidney disease. / Utilidad de los parámetros urinarios en la enfermedad renal crónica avanzada.

This review discusses the diagnostic value of urinary parameters in the setting of advanced chronic kidney disease and we present the key concepts that summarise the suggestions of the manuscript. URINARY VOLUME: The amount of fluid intake may be a non-established risk factor for CKD. For these patients, a urinary output ≥2-3 l/day is a reasonable proposal. This recommendation is not applicable to patients with cardiorenal syndrome or fluid overload risk. NA: This determination is very useful to monitor salt intake. Reducing urinary Na<120 mEq/day (≅salt intake≤5-6g) is a reasonable objective. URINARY UREA NITROGEN (UUN): This parameter is useful to estimate protein intake (Maroni BJ equation). A protein intake between 48-72g (0.8-0.9g/kg/day according to weight) is equivalent to UUN 7-10g/day approximately. ACID LOAD AND POTASSIUM: Acid load reduction may be an additional strategy in the nutritional management of this population. It may be estimated indirectly from a diet survey or by measuring the elimination of UUN and Kur. The limits of this recommendation have not been established, but we propose a cautious and prudent diet of fruit and vegetables. PHOSPHORUS: There is a significant positive correlation between phosphorus and protein, both in dietary records and urine elimination. Based on this information, we suggest a urinary P excretion<800mg/day or<600mg/day for patients with GFR<25ml/min or<15ml/min, respectively. CONCLUSION: Urinary parameters provide sensitive and useful knowledge for clinical practice, provide information about the dietary habits of patients and the adherence to our recommendations.

Vitamin D and proteinuria: a critical review of molecular bases and clinical experience.

Proteinuria is the main predictor of chronic kidney disease progression. Drugs that block the renin-angiotensin-aldosterone (RAA) system reduce proteinuria and slow down the progression of the disease. However, their effect is suboptimal, and residual proteinuria persists as an important predictor of renal impairment. Vitamin D has pleiotropic effects that could have an impact on these parameters. In this study, we critically review the molecular and experimental bases that suggest an antiproteinuric effect of vitamin D receptor (VDR) activation and the available evidence on its antiproteinuric effect in clinical practice. In animal models, we have observed the antiproteinuric effect of VDR activation, which could be due to direct protective action on the podocyte or other pleiotropic effects that slow down RAA system activation, inflammation and fibrosis. Clinical trials have generally been conducted in patients with a vitamin D deficiency or insufficiency and the main trial (VITAL) did not demonstrate that paricalcitol improved the study's primary endpoint (decrease in the urine albumin to creatinine ratio). In this sense, the information available is insufficient to advise the use of native vitamin D or VDR activators as renoprotective antiproteinuric drugs beyond the experimental level. Two Spanish clinical trials and one Italian trial attempted to determine the effect of paricalcitol and vitamin D on residual proteinuria in various clinical circumstances (PALIFE, NEFROVID and PROCEED).