Urinary Neutrophil Gelatinase-Associated Lipocalin (NGAL) as a Biomarker for Early Detection of AKI in Obstructive Uropathy

Background: Acute kidney injury (AKI) is a frequent complication of obstructive uropathy, often diagnosed late due to the limitations of conventional markers such as serum creatinine. Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a promising early biomarker released from injured tubular epithelium. Evaluating its role may provide critical insight into timely diagnosis and intervention. Methods: A prospective observational study was conducted at THQ Hospital Shujaabad on 60 patients with confirmed obstructive uropathy secondary to causes including urolithiasis, malignancy, and ureteral stricture. Urinary NGAL levels were measured at admission using ELISA, alongside serum creatinine and eGFR calculations. Patients were categorized based on the Kidney Disease: Improving Global Outcomes (KDIGO) criteria for AKI. Statistical analysis was performed using Epi Info™ version 7.2. Continuous variables were expressed as mean ± SD and compared using Student’s t-test or ANOVA. Pearson’s correlation coefficient was used to assess associations between NGAL and renal parameters. ROC curve analysis was used to determine the sensitivity, specificity, and diagnostic accuracy (AUC) of NGAL. Results: Urinary NGAL levels were significantly higher in the AKI group compared to non-AKI patients (mean ± SD: 425 ± 68 ng/mL vs. 146 ± 39 ng/mL, p < 0.001). NGAL showed a strong negative correlation with eGFR (r = -0.73, p < 0.01) and a positive correlation with serum creatinine (r = 0.68, p < 0.01). ROC analysis demonstrated an AUC of 0.89, with a sensitivity of 86% and specificity of 83% at a cut-off of 215 ng/mL. NGAL levels rose 24–48 hours earlier than serum creatinine in 78% of cases. Conclusion: Urinary NGAL is a sensitive, non-invasive, and early biomarker for AKI in obstructive uropathy. It significantly outperforms serum creatinine in early detection and may enable timely therapeutic interventions. Integration of NGAL testing into clinical protocols could enhance diagnostic accuracy and improve renal outcomes in at-risk patients.