Comparative Study between Fractional Excretion of Sodium and Fractional Excretion of Urea in Differentiating Prerenal From Renal Acute Kidney Injury in ICU Patients with Circulatory Shock

Abstract

Abstract Background The incidence of acute renal injury (AKI) in ICU is 5%. The mortality rate increases up to 50% if AKI is a part of multiple organ dysfunction syndrome. Aim of the Work Comparison between FENa and FEurea in differentiating renal from prerenal acute kidney injury in circulatory shock, and the effect of diuretics on their handling. Patients and Methods This retrospective study was conducted on 45 Egyptian patients with AKI complicating circulatory shock admitted to the ICUs of AIN SHAMS University Hospital, from August 2018 to February 2019. Consents were taken from all of them according to the local ethics committee approval. Results The cutoff points of both FENa and FEurea as a predictor of mortality were not statistically justified. This is explained as all our patients had circulatory shock, and so patients with mild renal impairment may die from their severe shock state, and patients with severe renal affection may survive if their shock could be rapidly corrected. This cutoff point calculation is recommended only in patients with AKI without other organ affections or shock that may affect the mortality. Conclusion Although both fractional excretion of urea (FEurea) and fractional excretion of sodium (FENa) are feasible, reproducible, and inexpensive markers used in differentiating renal from prerenal azotemia, in our study FEurea showed higher sensitivity and specificity than FENa, not only in differentiating renal from prerenal azotemia in critically ill patients complicating circulatory shock, but also its values were not affected by the use of diuretics like FENa in the same group of patients.