Overview Acute kidney injury (AKI) is the syndrome arising from a rapid fall in GFR (over hours to days). It is characterised by retention of both nitrogenous (including Urea and Creatinine) and non-nitrogenous waste products of metabolism, as well as disordered electrolyte, acid–base, and fluid homeostasis.
Remember AKI is neither a diagnosis nor a disease. Rather, it is a clinical syndrome that is caused by, or complicates, a wide range of disorders
Definition Acute Kidney Injury: Rapid reduction in kidney function over hours to days, as measured by serum urea and creatinine and leading to a failure to maintain fluid, electrolyte and acid-base homeostasis. Chronic Kidney Disease: Impaired renal function >3months based on abnormal structure or function, or GFR <60 for >3months. Oliguria: A urine output of <400ml/day may be the earlier sign of impaired renal function
Classification The aetiology of acute kidney injury can be simply divided into pre-renal, renal and post renal causes.
Pre-renal - Sepsis and hypotension
Severe sepsis
Haemorrhage
Dehydration
Cardiac failure
Liver failure
Renovascular insult
Intrarenal
Toxicity
Nephrotoxic drugs
Iodinated radiological contrast
Parenchymal kidney disease
Glomerulonephritis
Tubulointerstitial nephritis
Rhabdomyolysis
Haemolytic uraemic syndrome
Myeloma
Malignant hypertension
Post renal Obstruction
Bladder outflow
Stones
Tumour
Surgical ligation of ureters
Extrinsic compression (lymph nodes)
Retroperitoneal fibrosis
Approach to Acute Kidney Injury
History
Prerenal causes
Vomiting, diarrhoea, polyuria
Use of diuretics
Dehydration
Assess for comorbidities which may reduce renal perfusion - heart failure, shock
Renal causes
Diuretics and other nephrotoxins (NSAIDs, ARBs, ACEI)
Palpable purpura, pulmonary haemorrhage or sinusitis raises suspicion of systemic vasculitis with glomerulonepritis
Polyarthralgia, rash suggests rheumatological cause such as SLE
