Diagnostic Value Of Urinary Indices In Differentiating Pre-renal And Renal Acute Kidney Injury In Critically â…¢ Patients

Objective:To evaluate the diagnostic value of urinary indices in differentiating pre-renal and renal acute kidney injury (AKI) in critically ill patients.Design:A prospective cohort study.Setting:Medical Intensive Care Unit (ICU) of Peking Union Medical College Hospital.Participants:Adults who developed AKI at ICU admission or during ICU stay. Patients with post-renal AKI or renal replacement therapy (RRT) for chronic renal insufficiency were excluded, as well as those whose urine could not be collected.Intervention:We tested whether urinary indices distinguished between pre-renal and renal AKI, which were determined by tissue perfusion. Pre-renal AKI was defined as AKI with inadequate tissue perfusion and recovery within 24-72 hours after reversal of tissue hypoperfusion; renal AKI was defined as AKI with adequate tissue perfusion, or failure of AKI recovery within 24-72 hours after reversal of tissue hypoperfusion; intermediate AKI was defined as AKI with tissue hypoperfusion, and failure of reversal of both tissue perfusion and renal function. In addition, duration of AKI and renal blood flow measured by transesophageal echocardiography were used as the other two criteria of pre-renal and renal AKI to test the robustness of the diagnostic value of urinary indices.Results:49 patients with AKI were included.11 were defined as pre-renal AKI,19 as renal, and 19 as intermediate. Some of the urinary indices performed well in differential diagnosis (areas under the receiver operating characteristic curves 0.692-0.845), including urine specific gravity (SG), urine osmolality (Uosm), urine/plasma creatinine (U/P Cr), urine/plasma urea (U/P Urea), and fractional excretion of sodium (FeNa). The diagnostic accuracy of U/P Urea in differentiating pre-renal AKI was better than the other indices. Diagnostic value of these indices was generally maintained in the other two criteria and three subgroups (patients without diuretics, sepsis, or chronic renal insufficiency), where U/P Urea was better than the others.Conclusion:Some urinary indices (urine SG, Uosm, U/P Cr, U/P Urea and FeNa) were useful in differentiating pre-renal and renal AKI, with U/P Urea exhibiting higher accuracy and less susceptibility to diuretics, sepsis, and chronic renal insufficiency.