Función renal basal en pediatría: correlación de métodos que dependen de la recogida de orina de 24 h con otros más sencillos que no requieren orina minutada

IntroductionIn daily clinical practice a quick, easy and accessible method is needed to adequately assess renal function. The objectives of this study were: 1. To quantify the relationship and concordance of the glomerular filtration rate (GF) calculated by the clearance of creatinine in 24 h urine (CCr) and the original and modified Schwartz equation (SE); and 2. To correlate urine elimination of substances that depends on the volume of excreted urine in a unit of time with other parameters that are calculated measuring the concentration of these substances in blood and urine.Material and methodsThe study included 401 healthy children with ages between 3 to 14 years (187 male and 214 female). The analysis between the variables was carried out using Pearson's correlation coefficient and the intraclass correlation coefficient (ICC).ResultsThe correlation between values of CCr and the original SE (non-standardised creatinine measurement) was r = 0.58 (P < 0.001) and the concordance, ICC = 0.74. The correlation between CCr values and the modified SE (standardised creatinine measurement) was r = 0.68 (P < .001), and the concordance ICC = 0.78. There was a very significant correlation between the elimination of sodium in a 24 h urine (mEq/kg/24 h) and the Na-Fractional-Excretion (EFNa): r = 0.8 (P < .001). There was a correlation between the potassium elimination in 24 h (mEq/kg/24 h) and EFK: r = 0.85 (P < .001). Between volume/min/1.73 m² and the urine volume percent of GF was: r = 0.88 (P < .001).ConclusionsThese equations provide valuable information of the state of the basal renal function without having to use a timed urine.