Basal renal function in paediatric patients: Correlation of methods that depend on a 24 h urine collection with simpler methods that do not require a timed urine

Abstract

IntroductionIn the daily practice it is necessary to have quick, easy and accesible methods to adequately assess the renal function. The objectives were: 1. Quantify the relationship and concordance of the glomerular filtration rate (FG) calculated by the clearance of creatinine in 24 h urine (CCr) and the original and modified Schwartz equation (SE). 2. Correlate urine elimination of substances that depend 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. Materials and methodsThe study included 401 healthy children in the ages between 3 to14 (187 male and 214 female). The analysis between the variables was carried out by Pearson’s correlation coeficient and the intraclass correlation coefficient. ResultsThe correlation between values of CCr and the original SE (non standardized creatinine measuring) was r = 0.58 (P < 0.001) and the concordance, CCI = 0.74. Correlation between values of CCr and the modified SE (standardized creatinine measuring) was r = 0.68 (P < .001) and the concordance CCI = 0.78. There is a very significant correlation between the elimination of sodium in 24 h urine (mEq/Kg/24 h) and the Na-Fractional-Excretion (EFNa): r = 0.8 (P < .001). There was a correlation between the potasium elimination in 24 h (mEq/Kg/24 h) and EFK: r = 0.85 (P < .001). Between volume/minute/1.73 m² and the urine volume for each 100 ml FG was: r = 0.88 (P < .001). ConclusionsThese equations provide valuable information of the state of the basal renal function without having to turn to the minuted urine.