Acute Kidney Injury in the Intensive Care Unit: Recent Advances

Acute kidney injury (AKI) in the intensive care unit (ICU) is a heterogeneous syndrome characterized by kidney stress, structural injury, functional decline, requirement for extracorporeal organ support, and incomplete recovery, rather than a single creatinine-defined event. Current critical care practice increasingly integrates conventional Kidney Disease: Improving Global Outcomes (KDIGO) diagnostic criteria with urine output trajectories, cystatin C measurement when serum creatinine is unreliable, structural damage biomarkers when results will change management, hemodynamic phenotyping, venous congestion assessment, nephrotoxin stewardship, fluid stewardship, and recovery planning. This narrative review summarizes recent advances relevant to adult ICU care, including evolving definitions of AKI and acute kidney disease, sepsis-associated microcirculatory and cellular injury, systemic venous congestion, point-of-care ultrasound-assisted congestion assessment, biomarker-triggered prevention bundles, individualized renal replacement therapy (RRT), continuous renal replacement therapy (CRRT), and post-ICU recovery pathways. Key recommendations include avoiding automatic fluid loading in response to oliguria; interpreting mean arterial pressure together with cardiac output, central venous pressure, right ventricular function, and intra-abdominal pressure; using biomarkers only within an actionable response pathway; and initiating RRT according to urgent or trajectory-based indications rather than serum creatinine alone. Precision ICU nephrology is best conceptualized as the timely alignment of phenotype, risk, trajectory, and organ support objectives.