What is the objective definition of Acute Kidney Injury (AKI)?

From the Guidelines

Acute Kidney Injury (AKI) is objectively defined as an increase in serum creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days or urine volume less than 0.5 mL/kg/hr for 6 hours, as per the most recent and widely accepted KDIGO criteria 1. The definition of AKI is crucial for early recognition and intervention, as it can lead to severe complications such as electrolyte imbalances, metabolic acidosis, fluid overload, and increased mortality if not promptly addressed. Some key points to consider in the definition of AKI include:

• An increase in serum creatinine by 0.3 mg/dL within 48 hours is a key criterion for diagnosing AKI 2, 3
• An increase in serum creatinine to 1.5 times baseline within 7 days is another important criterion for AKI diagnosis 2, 3
• Urine volume less than 0.5 mL/kg/hr for 6 hours is also a critical factor in defining AKI 2, 3 The pathophysiology of AKI involves reduced kidney perfusion, direct tubular injury, or urinary tract obstruction, with causes ranging from prerenal (decreased blood flow), intrinsic (direct kidney damage), to postrenal (urinary obstruction) factors 2. Monitoring serum creatinine and urine output in at-risk patients is essential for timely diagnosis and management of AKI, as emphasized by the KDIGO guidelines 1. It is worth noting that the KDIGO criteria have been widely adopted and are considered the gold standard for defining and staging AKI 1. In clinical practice, it is essential to be aware of the risk factors for AKI, such as hypotension, hypovolemia, and exposure to nephrotoxic agents, and to monitor patients closely for signs of kidney injury 2, 3. By using the KDIGO criteria and being vigilant for signs of AKI, healthcare providers can promptly diagnose and manage this condition, reducing the risk of complications and improving patient outcomes 1.

From the Research

Definition of Acute Kidney Injury (AKI)

• Acute kidney injury (AKI) is characterized by an abrupt decrease in renal function or the onset of frank renal failure 4.
• AKI is defined as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 4, 5.
• AKI can also be defined as an increase in serum creatinine or a decrease in urine output over hours to days 6.

Key Characteristics of AKI

• AKI is a syndrome in which the kidney plays an active role in the progression of multi-organ dysfunction 7.
• The incidence rate of AKI is increasing and becoming a common and serious disease affecting public health costs worldwide 7.
• AKI is classically defined and staged based on serum creatinine concentration and urine output rates 8.

Diagnosis and Classification of AKI

• The etiology of AKI is conceptually classified into three general categories: prerenal, intrarenal, and postrenal 8.
• A thorough history and physical examination can help categorize the underlying cause of AKI 6.
• The Kidney Disease: Improving Global Outcomes (KDIGO) group has established consensus definitions for AKI, which refer to the time of AKI development and are based on serum creatinine level increase and/or urine output decrease 5.