From the Guidelines
Acute Kidney Injury (AKI) is a sudden loss of kidney function that occurs over 7 days or less, characterized by a rise in creatinine levels or a decrease in urine output.
Definition and Staging
The definition and staging of AKI are based on the Kidney Disease Improving Global Outcomes (KDIGO) guidelines, which define AKI as an increase in serum creatinine by ≥0.3 mg/dl within 48 hours or a 50% increase from baseline within 7 days, or a urine output of <0.5 ml/kg/h for 6 hours 1. The staging of AKI is as follows:
- Stage 1: Rise of >26 mmol/l or 0.3 mg/dl within 48 h or 50–99% creatinine rise from baseline within 7 days
- Stage 2: 100–199% creatinine rise from baseline within 7 days
- Stage 3: >200% creatinine rise from baseline within 7 days or any requirement for renal replacement therapy
Diagnosis and Detection
The initial diagnosis of AKI is based on the early change in a marker of AKI, such as serum creatinine or urine output, and needs to be carried out in real-time 1. Staging of AKI is done retrospectively at the end of the episode, based on the maximum severity of AKI.
Relationship to Acute Kidney Disease (AKD) and Chronic Kidney Disease (CKD)
AKI is a subset of AKD, which is a term used to describe the course of disease after AKI among patients in whom the renal pathophysiologic processes are ongoing 1. AKD can progress to CKD, and patients with AKD are at increased risk of developing CKD and end-stage renal disease (ESRD) 1.
Clinical Implications
The diagnosis and staging of AKI have important implications for clinical practice, including the need for timely and appropriate management to prevent progression to CKD and ESRD 1. The KDIGO guidelines recommend the use of a definition, such as KDIGO for adults and pediatric RIFLE (pRIFLE) for children, in routine clinical practice 1.
From the Research
Definition of Acute Kidney Injury (AKI)
- Acute kidney injury (AKI) is a syndrome of impaired kidney function associated with reduced survival and increased morbidity 2.
- AKI is defined by a sudden loss of excretory kidney function 3.
- It is characterized by a rapid increase in serum creatinine, decrease in urine output, or both 4.
- AKI is not considered a pathological condition of single organ failure, but a syndrome in which the kidney plays an active role in the progression of multi-organ dysfunction 5.
Causes and Epidemiology of AKI
- AKI can be caused by various factors, including infections, hypovolaemic shock, sepsis, drugs, and invasive procedures 3.
- The incidence rate of AKI is increasing and becoming a common (8-16% of hospital admissions) and serious disease (four-fold increased hospital mortality) affecting public health costs worldwide 5.
- AKI occurs in approximately 10-15% of patients admitted to hospital, while its incidence in intensive care has been reported in more than 50% of patients 4.
Consequences and Management of AKI
- AKI has a poor prognosis in critically ill patients, with long-term consequences including chronic kidney disease (CKD) and cardiovascular morbidity 3.
- The management of AKI in critical care settings is challenging, including appropriate volume control, nephrotoxic drug management, and the timing and type of kidney support 3.
- Fluid and electrolyte management are essential, and kidney replacement therapy is frequently required 3.
- Biomarkers of kidney injury or stress are new tools for risk assessment and could possibly guide therapy 4.