Acute kidney injury (AKI)

Acute kidney injury

• acute kidney injury (AKI)
  • previously known as acute renal failure, encompasses a wide spectrum of injury to the kidneys, not just kidney failure (1)
    
    
  • definition of acute kidney injury has changed in recent years, and detection is now mostly based on monitoring creatinine levels, with or without urine output
    
    
  • is seen in 13% to 18% of all people admitted to hospital, with older adults being particularly affected (1)
    
    
  • incidence significantly increases with progressive severity of the underlying cause: up to 50% of the patients treated at the intensive care unit develop AKI, in many cases as a results of generalized infection or sepsis (2)
    
    
  • prognosis has not significantly been improved during the last 20-30 years, although substantial progress has been achieved in intensive care medicine and dialysis treatment, respectively (2)
    • in the mid-nineteen seventies 70% of all patients with AKI died. Mortality moderately decreased until the early nineties (30-50%) and remained stable over the last 20 years
    • poor prognosis partly results from the disease leading to AKI per se but also ensues from complications associated with 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 (1)

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

Staging of 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. NICE (September 2023). Acute kidney injury - Prevention, detection and management of acute kidney injury up to the point of renal replacement therapy
2. Patschan D, Muller GA. Acute kidney injury. J Inj Violence Res. 2015 Jan;7(1):19-26.