Dynamic Changes in Serum Neutrophil Gelatinase-Associated Lipocalin for Discrimination of Creatinine-Defined Acute Kidney Injury After Laparoscopic Sleeve Gastrectomy: A Prospective Observational Cohort Study

Background/Objectives: Acute kidney injury (AKI) may occur after laparoscopic sleeve gastrectomy (LSG) as a result of obesity-related renal vulnerability, pneumoperitoneum-induced changes in renal perfusion, and perioperative hemodynamic stress. Serum creatinine remains the standard diagnostic marker for AKI; however, it may not fully reflect perioperative renal stress. This study aimed to evaluate the diagnostic performance of serum neutrophil gelatinase-associated lipocalin (NGAL), particularly dynamic changes in NGAL (ΔNGAL), for discriminating between patients with and without postoperative AKI after LSG. Methods: This prospective observational cohort study included 60 patients with severe obesity who underwent LSG at a tertiary referral center. Serum NGAL, serum creatinine, blood urea nitrogen, and estimated glomerular filtration rate were measured preoperatively and on postoperative days 1 and 3. AKI was defined according to creatinine-based Kidney Disease: Improving Global Outcomes criteria. Patients were compared according to postoperative AKI status. ΔNGAL and changes in renal function parameters were analyzed, and receiver operating characteristic curve analysis was performed to assess diagnostic performance. Results: AKI developed in 6 patients (10%). Postoperative day 1 NGAL levels were significantly higher in patients who developed AKI than in those who did not. ΔNGAL from preoperative baseline to postoperative day 1 was significantly greater in the AKI group. ROC analysis demonstrated that ΔNGAL had strong discriminatory performance for postoperative AKI, with an area under the curve of 0.901, sensitivity of 83.3%, and specificity of 90.7% at an exploratory cut-off value of 57.2 ng/mL. Absolute NGAL values showed lower diagnostic performance than ΔNGAL. Conclusions: Dynamic changes in serum NGAL should not be interpreted as a replacement for creatinine-based AKI criteria but may be considered a complementary biomarker associated with perioperative renal stress in selected bariatric surgery patients.