Definition
- Increase in serum creatinine by 26.5 micromol/l over 48h; or
- Increase in serum creatinine >1.5 times baseline within 7 days
- Urine volume <0.5 ml/kg/h for 6 hours
Risk Factors
- CKD (eGFR less than 60 ml/min/1.73m2, CKD stage 3-5)
- Previous AKI
- Sepsis
- Heart failure
- Liver disease
- Diabetes
- Hypovolaemia
- Drugs: NSAIDs, aminoglycosides (gentamicin), ACE inhibitors, ARBs, diuretics. (Metformin is not nephrotoxic but is exclusively excreted via the kidneys; administration in AKI causes lactic acidosis)
- Iodinated contrast within the past week
- Pathologies causing renal out-flow obstruction
- >65 years
Causes
- Pre
- Dehydration/hypovolemia
- Intra
- Glomerular disease: glomerulonephritis, thrombosis, haemolytic uraemic syndrome.
- Tubular injury: ATN, nephrotoxins (aminoglycosides, radiocontrast media, myoglobin, cisplatin, heavy metals, light chains in myeloma kidney).
- Acute interstitial nephritis: NSAIDs, Paracetamol, infection or autoimmune disease
- Vascular disease: vasculitis (usually associated with ANCA)
- Eclampsia
- Post
- Intrinsic or extrinsic obstruction of urinary out-flow tract
Investigation
- Urine dipstick – refer to nephrology for investigation of glomular nephritis if positive for protein and blood
- USS – within 6h when pyonephritis expected; within 24h when no cause evident/obstruction possible
- Immunology
- Free kappa/lambda light chain assay, serum protein electrophoresis, Bence Jones’ proteinuria: immune paresis, monoclonal band on serum protein electrophoresis, and Bence Jones’ proteinuria suggest myeloma.
- ANA: positive in systemic lupus erythematosus (SLE) and other autoimmune disorders, anti-double-stranded DNA antibodies more specific for SLE
- ANCA: c-ANCA and anti-PR3 associated with Wegener’s granulomatosis; p-ANCA and anti-MPO associated with microscopic polyangiitis
- Complement concentrations: low in SLE, acute post-infectious glomerulonephritis, cryoglobulinaemia
- anti-GBM antibodies: Goodpasture’s syndrome.
- Antistreptolysin O and anti-DNase B titres: high after streptococcal infection.
- CK (rhabdomyalis)
- New biomarkers: cystatin C, NGAL, KIM-1, IL-18. None currently in routine use
Resources
NICE Acute Kidney Injury, CG 196, 2013
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