Acute Kidney Injury Part 1:
Classification of the aetiology of Acute Kidney Injury (AKI, Acute Renal Failure )
Table 1: Aetiology of Acute Kidney Injury
- Results from a compromise to renal perfusion and oxygen supply
- Is commonly due to hypovolaemia or hypotension
- Is reversible with early adequate resuscitation (see assessment of the critically ill patient module).
- Can be potentiated by a number of medicines, including non-steroidal agents, ACE inhibitors and angiotensin II antagonists which should be stopped. If there is a strong indication for an ACE inhibitor consider restarting following recovery with close monitoring of renal function.
- Shock and toxins can result in damage to the renal parenchyma with acute tubular necrosis, therefore pre-renal and intrinsic renal causes of acute kidney injury may co-exist.
- Usually result from renal artery disease and aortic atheroma/cholesterol emboli.
- Cholesterol emboli commonly follow intervention e.g. angiography or on commencement of anticoagulation.
Remember: patients with a systemic vasculitis (microscopic polyarteritis, Wegener’s syndrome, SLE) may present with multiple organ failure and mimic sepsis. Have a high index of suspicion: early immunotherapy may save life and functional renal tissue.
- All mediated through direct damage to the renal parenchyma
- Acute tubular necrosis
• Drugs: NSAIDs, aminoglycosides, paracetamol in overdose.
• Poisons: methanol, ethylene glycol.
• Contrast media.
- Specific conditions
- Vasculitis/glomerulonephritis: is there a history of skin rash, arthralgia/arthritis, rigors?
- Accelerated phase hypertension.
- Interstitial nephritis: follows a period of drug exposure in most instances.
- Infections: legionella, leptospirosis, malaria.
- Results from blockage to urinary flow.
- This implies that both ureters are blocked or that outflow from a single functioning kidney has been impeded.
- Renal tubules/pelvis, ureters with myoglobinuria, haemoglobinuria, crystal formation eg uric acid in tumour lysis syndrome, myeloma and papillary sloughing (e.g. diabetes).
- Ureteric/urethral as in prostatic hypertrophy or bladder/ureter blockage as a result of tumour, stone, clot or stricture.