Research
Diagnostic performance of fractional excretion of urea in the evaluation of critically ill patients with acute kidney injury: a multicenter cohort study
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* Corresponding author: Michael Darmon michael.darmon@chu-st-etienne.fr
1 Medical-Surgical Intensive Care Unit, Saint-Etienne University Hospital, and Jean Monnet University, Avenue Albert Raymond, F-42270 Saint-Etienne, France
2 INSERM Unit 955, Paris-12 University, 51 Avenue du Marechal De Lattre de Tassigny, F-94010 Créteil, France
3 Thrombosis Research Group, EA 3065, Saint-Etienne University Hospital, and Saint-Etienne Medical School, Avenue Albert Raymond, F-42270 Saint-Etienne, France
4 Medical-Surgical Intensive Care Unit, Avicenne University Hospital, APHP, 125, rue de Stalingrad, F-93009 Bobigny, France
5 Medical Intensive Care Unit, Archet University Hospital, Nice, France; and Nice University, UFR de Médecine, 151 Rte Saint Antoine Ginestiere, F-06202 Nice, France
6 Medical Intensive Care Unit, AP-HP, Albert Chenevier-Henri Mondor University Hospital, and Paris-12 University, 51 Avenue du Marechal De Lattre de Tassigny, F-94010 Créteil, France
7 Medical ICU, Saint-Louis University Hospital, APHP, Avenue Claude Vellefaux, F-75010 Paris, France; and UFR de Médecine, Paris-7 Paris-Diderot University, Avenue Claude Vellefaux, F-75010 Paris, France
8 Medical-Surgical Intensive Care Unit, Hôpitaux Universitaires de Genève, 24, Micheli-du-Crest, CH-1211 Genève 14, Suisse
9 Paris-13 University, 125, rue de Stalingrad, F-93009 Bobigny, France
Critical Care 2011, 15:R178 doi:10.1186/cc10327
Published: 27 July 2011Abstract
Introduction
Several factors, including diuretic use and sepsis, interfere with the fractional excretion of sodium, which is used to distinguish transient from persistent acute kidney injury (AKI). These factors do not affect the fractional excretion of urea (FeUrea). However, there are conflicting data on the diagnostic accuracy of FeUrea.
Methods
We conducted an observational, prospective, multicenter study at three ICUs in university hospitals. Unselected patients, except those with obstructive AKI, were admitted to the participating ICUs during a six-month period. Transient AKI was defined as AKI caused by renal hypoperfusion and reversal within three days. The results are reported as medians (interquartile ranges).
Results
A total of 203 patients were included. According to our definitions, 67 had no AKI, 54 had transient AKI and 82 had persistent AKI. FeUrea was 39% (28 to 40) in the no-AKI group, 41% (29 to 54) in the transient AKI group and 32% (22 to 51) in the persistent AKI group (P = 0.12). FeUrea was of little help in distinguishing transient AKI from persistent AKI, with the area under the receiver operating characteristic curve being 0.59 (95% confidence interval, 0.49 to 0.70; P = 0.06). Sensitivity was 63% and specificity was 54% with a cutoff of 35%. In the subgroup of patients receiving diuretics, the results were similar.
Conclusions
FeUrea may be of little help in distinguishing transient AKI from persistent AKI in critically ill patients, including those receiving diuretic therapy. Additional studies are needed to evaluate alternative markers or strategies to differentiate transient from persistent AKI.