urine sodium excretion rate urine fractional sodium excretion 2013-11-04T15:20:59Z A calculated measurement of the fraction of sodium actually excreted in the urine relative to the amount filtered by the kidneys. It is calculated as the clearance of sodium divided by the glomerular filtration rate. The standard equation for the calculation is: ((urineSodium x plasmaCreatinine)/(plasmaSodium x urineCreatinine))x100. CMO:0001850 JSmith VT:0006274 clinical_measurement_ontology urinary fractional excretion of sodium calculated urine electrolyte excretion rate