GPAtlas🧭 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 – but 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, so the key skill in primary care is to compare today's creatinine with the patient's baseline, sort the likely cause into one of three buckets, and 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), and 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 / hypotension, heart failure, hepatorenal syndrome, renal artery compromise (ACE inhibitor / 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 / 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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