Lecture 1 of 8
Clinical Approach to the Diagnosis of AKI: Overview
A structured framework for evaluating suspected AKI — definition, KDIGO criteria, and the initial differential.
Definition (KDIGO)
- AKI = abrupt (hours–days) reduction in kidney function with retention of nitrogenous waste and dysregulation of fluid/electrolyte/acid-base.
- Diagnostic criteria: ↑ SCr ≥0.3 mg/dL within 48 h, or ≥1.5× baseline within 7 days, or urine output <0.5 mL/kg/h for ≥6 h.
- Baseline creatinine is critical — estimate from the most recent stable value, not the admission value.
Initial Structured Approach
- Confirm AKI (vs chronic or AKI-on-CKD) — compare to baseline and trend the creatinine.
- Stage severity (KDIGO 1–3) — guides monitoring intensity and dialysis threshold.
- Classify etiology into Pre-renal, Intrinsic (intra-renal), Post-renal — the classic triage.
- Identify reversible contributors early: hypovolemia, nephrotoxins, obstruction, sepsis.
Red Flags Prompting Urgent Action
- Hyperkalemia (K⁺ ≥6.0 or ECG changes), severe acidosis (pH <7.1), volume overload with hypoxemia.
- Uremic symptoms (pericarditis, encephalopathy), anuria, or rapidly rising creatinine.
- Suspected obstruction with infection, or rapidly progressive glomerulonephritis.