Other causes

• Nephrotoxins — may cause renal failure via acute tubular necrosis, interstitial nephritis or renal tubular obstruction. All potential nephrotoxins should be withdrawn.

• Rhabdomyolysis — suggested by myoglobinuria and raised CPK in patients who have suffered a crush injury, coma or seizures.

• Glomerular disease — red cell casts, haematuria, proteinuria and systemic features (e.g. hypertension, purpura, arthralgia, vasculitis) are all suggestive of glomerular disease. Renal biopsy or specific blood tests (e.g. Goodpasture's syndrome, vasculitis) are required to confirm diagnosis and appropriate treatment.

• Haemolytic uraemic syndrome — suggested by haemolysis, uraemia, thrombocytopenia and neurological abnormalities.

• Crystal nephropathy—suggested by the presence of crystals in the urinary sediment. Microscopic examination of the crystals confirms the diagnosis (e.g. urate, oxalate). Release of purines and urate are responsible for acute renal failure in the tumour lysis syndrome.

• Renovascular disorders — loss of vascular supply may be diagnosed by renography. Complete loss of arterial supply may occur in abdominal trauma or aortic disease (particularly dissection). More commonly, the arterial supply is partially compromised (e.g. renal artery stenosis) and blood flow is further reduced by haemodynamic instability or locally via drug therapy (e.g. NSAIDs, ACE inhibitors). Renal vein obstruction may be due to thrombosis or external compression (e.g. raised intra-abdominal pressure).

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