Abnormal renal tubular resorption Impaired renal tubular reabsorption of sodium 2022-09-04T19:45:17Z Increased fractional excretion (FE) of sodium in the urine. The FE of sodium is the percentage of the sodium filtered by the kidney which is excreted in the urine. It is measured in terms of plasma and urine sodium, rather than by the interpretation of urinary glucose concentration alone, as urinary glucose concentrations can vary with water reabsorption.