Novel biomarker–based assessment of acute kidney injury in thePediatric Intensive Care Unit

Acute kidney injury (AKI) is a common and serious complication in pediatric intensive care units (PICUs), often associated with increased morbidity and mortality. Early detection is critical, yet traditional markers like serum creatinine and urine output are limited by delayed response. This study aimed to evaluate urinary neutrophil gelatinase-associated lipocalin (NGAL), interleukin-9 (IL- 9) and olfactomedin-4 (OLFM-4) as early biomarkers for AKI in critically ill pediatric patients. This prospective, single-center study included 55 patients admitted to the PICU of Eskişehir Osmangazi University Hospital between October 2024 and April 2025. AKI diagnosis and staging were performed using both pRIFLE and KDIGO criteria. Urine samples were collected at admission (0 hours), 48 hours, and 72 hours. Urinary NGAL, IL-9, and OLFM-4 levels were measured via ELISA. Patients who developed AKI (n=30) were compared with those who did not (n=25). Urinary NGAL and IL-9 levels were significantly elevated in the AKI group compared to controls at all time points (p<0.001 for NGAL; p<0.001, p<0.05 and p<0.001 for IL-9 at 0., 48th and 72nd hours of the study). Urinary OLFM-4 levels were significantly higher at admission in the AKI group (p<0.01) but not at 48 or 72 hours (p>0.05). Urinary NGAL levels positively correlated with urinary IL-9 and OLFM-4 levels, serum BUN, and creatinine levels, and negatively correlated with urine output (all p<0.001). No significant differences in biomarker levels were observed based on sepsis status, AKI stage, or requirement for renal replacement therapy. In conclusion, urinary NGAL and IL-9 are promising markers for the early diagnosis of AKI in pediatric intensive care patients; however, the diagnostic contribution of urinary OLFM-4 levels is limited. In light of these findings, the effectiveness of urinary NGAL and IL-9 levels in the early diagnosis and treatment of ABH cases in pediatric patients can be evaluated through broader studies, and their use in routine protocols can be decided.