Acute Kidney Injury (AKI)

🔍 When to Suspect

Reduced urine output (oliguria), swelling in legs/ankles/feet (oedema), and shortness of breath, especially with dehydration, sepsis, blood loss, or use of nephrotoxic drugs (NSAIDs, ACE inhibitors)

From the full topic in The Ocean Library: Acute Kidney Injury (AKI)

🧭 When to suspect

Suspect acute kidney injury (AKI) in any acutely unwell patient with reduced urine output (oliguria), swelling of the legs, ankles or feet (oedema), or breathlessness.

Remember that AKI is frequently silent, picked up only as a rising creatinine on bloods taken for another reason.

AKI is a syndrome, not a diagnosis. It is defined by a measured change in kidney function.

• Compare today's creatinine with the patient's baseline.

• Sort the likely cause into one of three buckets.

• Never miss a reversible cause – volume depletion or obstruction.

• Raise suspicion particularly with precipitants such as dehydration (vomiting, diarrhoea), sepsis, significant blood loss, contrast exposure, or nephrotoxic drugs (NSAIDs, ACE inhibitors, ARBs, diuretics).

• Raise suspicion also in those with CKD, diabetes, heart failure or liver disease.

Category	Common causes
Pre-renal (reduced perfusion – the commonest)	Hypovolaemia (D&V, haemorrhage, burns), sepsis or hypotension, heart failure, hepatorenal syndrome, renal artery compromise (ACE inhibitor or NSAID effect).
Intrinsic (renal)	Acute tubular necrosis (ischaemic or toxic – the commonest intrinsic cause), glomerulonephritis, vasculitis, acute interstitial nephritis (drugs – PPIs, antibiotics, NSAIDs), rhabdomyolysis, myeloma.
Post-renal (obstruction)	Prostatic enlargement, renal or ureteric stones, pelvic or abdominal tumour, retroperitoneal fibrosis, blocked catheter.

Severity is graded by the rise in creatinine (or fall in urine output) against baseline, and the stage drives urgency – stage 3 warrants same-day specialist discussion.

Stage	Serum creatinine	Urine output
1	1.5–1.9× baseline, or a rise of ≥ 26 µmol/L in 48 h	< 0.5 mL/kg/h for 6–12 h
2	2.0–2.9× baseline	< 0.5 mL/kg/h for ≥ 12 h
3	≥ 3× baseline, or ≥ 354 µmol/L, or started on renal replacement therapy	< 0.3 mL/kg/h for ≥ 24 h, or anuria ≥ 12 h

Source: NICE NG148 · UK Kidney Association

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