The Evolution of the Fractional Excretion of Urea as a Diagnostic Tool in Oliguric States  Charles J. Diskin, MD, Thomas J. Stokes, MD, Linda M. Dansby, MD, Lautrec Radcliff, MD, Thomas B. Carter, DO  American Journal of Kidney Diseases  Volume 51, Issue 5, Pages 869-870 (May 2008) DOI: 10.1053/j.ajkd.2007.12.047 Copyright © 2008 National Kidney Foundation, Inc. Terms and Conditions

Figure 1 (A) Use of the fractional excretion of sodium to predict prerenal azotemia. Of the first 35 patients seen, 30 were found to have prerenal azotemia, but only 11 (36%) were found to have fractional excretion of sodium less than 1.0% (true positives), while 8 (all of whom were taking diuretics) were greater than 3.0% (false negatives). Of the 5 patients with intrinsic renal disease, 4/5 (true negatives) were greater than 3.0%. There were no false positives. The original criteria of Espinel4 was used where a fractional excretion of sodium greater than 1% but less than 3% was considered indeterminate. (B) Use of the fractional excretion of urea to predict prerenal azotemia. Of 30 patients with prerenal azotemia, 29 (97%) had a fractional excretion of urea of less than 40% (true positives; p=0.001). There was one false negative and for the 5 patients with intrinsic renal disease, all were true negatives. American Journal of Kidney Diseases 2008 51, 869-870DOI: (10.1053/j.ajkd.2007.12.047) Copyright © 2008 National Kidney Foundation, Inc. Terms and Conditions