Staging of acute kidney injury (AKI)

Staging of AKI

Definition of AKI

Acute kidney injury is defined when one of the following criteria is met

• serum creatinine rises by >= 26 µmol/L within 48 hours or
  
  
• serum creatinine rises >= 1.5 fold from the reference value, which is known or presumed to have occurred within one week or
  
  
• oliguria (urine output is < 0.5ml/kg/hr for >6 consecutive hours) or
  
  
• a 25% or greater fall in eGFR in children and young people within the past 7 days (3)

The reference serum creatinine should be the lowest creatinine value recorded within 3 months of the event

If a reference serum creatinine value is not available within 3 months and AKI is suspected

• repeat serum creatinine within 24 hours
• a reference serum creatinine value can be estimated from the nadir serum creatinine value if patient recovers from AKI

Notes:

• formula-based estimated GFR should be interpreted with caution in AKI - this is because the formulae rely on a stable serum creatinine concentration
• is a clinical syndrome characterised by a rapid decline in excretory function occurring over a period of hours or day
• if a patient has suspected AKI the s/he should be referred to a nephrologist
• acute on chronic renal failure
  • if there has been a fall in estimated GFR of >25% since the last measurement of kidney function in a patient with CKD should prompt a repeat measurement of kidney function, assessment as for AKI and referral if the deterioration is confirmed

Reference:

1. The Renal Association (May 2006).UK CKD Guidelines
2. UK Renal Association (2011). Acute Kidney Injury
3. NICE (August 2013). Acute kidney injury - Prevention, detection and management of acute kidney injury up to the point of renal replacement therapy