BackgroundNeutrophil gelatinase-associated lipocalin (NGAL) is a diagnostic marker for acute kidney injury (AKI). NGAL expression is highly induced not only in kidney injury but also in bacterial infection, inflammation, and cancer. The factors regulating NGAL expression are proinflammatory cytokines, and plasma NGAL levels have been increased in septic shock. However, there are no reports of urine neutrophil gelatinase-associated lipocalin (uNGAL) levels after open esophagectomy.MethodsWe prospectively enrolled critically ill patients, including patients with sepsis (n = 45) and patients who underwent open esophagectomy (n = 40). We compared vital signs, PaO2/FIO2, serum C-reactive protein (CRP) levels, acute physiology and chronic health evaluation (APACHE) II score, sequential organ failure assessment (SOFA) score, and uNGAL levels between the sepsis group and the esophagectomy group. Then, we investigated whether uNGAL is associated with the severity of illness and organ failure, and whether uNGAL is a reliable screening test for AKI.ResultsThe median uNGAL levels, APACHE II score, SOFA score, and serum CRP levels were significantly (p < 0.001) higher in the sepsis group than in the esophagectomy group on ICU day 1. In the sepsis group, uNGAL levels were significantly (p < 0.05) correlated with APACHE II score and SOFA score on intensive care unit (ICU) day 1, 2, and 3. In the esophagectomy group, uNGAL levels were significantly (p < 0.05) correlated with SOFA score on ICU day 3 and 4. In the sepsis group, 1 patient developed AKI stage 2 and 6 patients developed AKI stage 3. No patients developed AKI in the esophagectomy group. In a total of 85 patients of this study, 80 patients had an abnormal value of uNGAL and only 7 patients (8.7%) of those 80 patients developed AKI.ConclusionsuNGAL levels were correlated with the severity of illness and organ failure in critically ill patients. The value of uNGAL increases under the surgical and inflammatory responses, thereby losing a significance of a screening test of AKI in critically ill patients.