ICU-acquired acute kidney injury in critically ill adults: a retrospective cohort study of risk factors and KDIGO stage dynamics in a Brazilian ICU

Acute kidney injury (AKI) is a frequent complication in critically ill patients, and early recognition of risk factors may support preventive care. We conducted a retrospective cohort study in a single-center Brazilian ICU from 2015 to 2022 to identify factors associated with ICU-acquired AKI and to describe KDIGO trajectories. Adults with ICU stay ≥48 hours were included; patients with chronic kidney disease, AKI on admission, or no serum creatinine measurement were excluded. Analyses included a multivariable Fine-Gray model with ICU death as a competing event, a Bayesian network for conditional dependencies, and descriptive KDIGO dynamics. Among 2935 patients, 794 (27.1%) developed AKI. The final model retained age (sHR 1.05 per 10 years; 95%CI 1.01-1.10), chronic liver disease (1.95; 95%CI 1.11-3.43), immunosuppression (1.93; 95%CI 1.29-2.87), hypertension (1.26; 95%CI 1.06-1.50), underweight BMI (1.33; 95%CI 1.05-1.69), mechanical ventilation on admission (1.50; 95%CI 1.19-1.90), admission arterial lactate (1.06 per 1 mmol/L; 95%CI 1.03-1.10), and leukocyte count (1.02 per 10,000 cells/µL; 95%CI 1.00-1.03). Among AKI cases, the proportion classified as KDIGO stage 3 increased after day 7, largely driven by renal replacement therapy among patients remaining in the ICU. These findings highlight that early admission markers of vulnerability and illness severity are associated with ICU-acquired AKI and support early risk recognition and kidney-protective care in the ICU course.