Acute kidney injury (AKI)
Definition
Acute kidney injury (AKI) is a rapid decline in renal excretory function over hours to days causing disturbances of fluid balance, electrolytes and acid-base homeostasis. The term AKI covers the full spectrum from small biochemical change to life‑threatening renal failure requiring renal replacement therapy (RRT) (NICE NG148).
Why AKI matters in the ED
- AKI is common in acute presentations and independently increases morbidity, length of stay and mortality.
- The ED is the key point for early detection and for reversing common, reversible causes such as hypovolaemia, obstruction, sepsis and nephrotoxins.
- Emergency departments must have fail‑safe systems to ensure creatinine and electrolytes are reviewed and actioned before discharge or handover (RCEM guidance).
Diagnostic thresholds and staging (adult criteria; NICE NG148)
Always compare with a reliable baseline creatinine where possible; interpret isolated values in clinical context if baseline is unavailable (NICE NG148).
A pragmatic ED approach
1. Who to test (screening triggers) Measure serum creatinine (and compare to baseline) in adults with acute illness and any of the following risk factors:
- Known chronic kidney disease (especially stage 3 or higher).
- Age ≥65 years.
- Heart failure or liver disease.
- Sepsis or hypotension.