From the Guidelines
Acute Kidney Injury (AKI) is primarily caused by prerenal, renal, or postrenal factors, with prerenal and renal etiologies accounting for over 97% of AKI cases. The causes of AKI can be broadly categorized into three main groups:
- Pre-renal causes: These result from decreased blood flow to the kidneys, including: + Hypovolemia (e.g., dehydration, blood loss) 1 + Low cardiac output (e.g., heart failure, shock) + Medications affecting renal blood flow (e.g., NSAIDs, ACE inhibitors)
- Intrinsic renal causes: These involve direct damage to the kidney tissue, including: + Acute tubular necrosis (ATN) from ischemia or toxins + Glomerulonephritis + Interstitial nephritis (often drug-induced) + Vascular diseases (e.g., vasculitis, thrombotic microangiopathy)
- Post-renal causes: These involve obstruction of urine outflow, including: + Urinary tract obstruction (e.g., kidney stones, tumors, enlarged prostate) + Bladder dysfunction To determine the specific etiology, a thorough clinical assessment is crucial, including patient history, physical examination, laboratory tests (e.g., urinalysis, serum creatinine), and imaging studies when appropriate, as recommended by recent guidelines 2, 3. Identifying the underlying cause is essential for appropriate management and prevention of further kidney damage. Understanding these etiologies helps in developing targeted treatment strategies and implementing preventive measures in high-risk patients, such as maintaining adequate hydration, avoiding nephrotoxic medications when possible, and promptly treating underlying conditions, which can help prevent or mitigate AKI in many cases 1.
From the Research
Causes of Acute Kidney Injury (AKI)
The causes of AKI can be conceptually classified into three general categories: prerenal, intrarenal, and postrenal 4. Some of the specific causes of AKI include:
- Infections and hypovolaemic shock, which are the predominant causes of AKI in low-income and middle-income countries 5
- Sepsis, drugs, or invasive procedures, which are common causes of AKI in high-income countries, particularly in elderly patients who are in hospital 5
- Ischemia or nephrotoxicity, which can cause acute tubular necrosis, a common condition in the setting of AKI 4
- Decreased renal perfusion, which is a common cause of AKI in hospitalized patients 6
- Drug-induced, contrast-associated, postoperative, and sepsis-associated AKI, which can also occur in hospitalized patients 6
- Kidney hypoperfusion, abdominal compartment syndrome, and urinary tract obstruction, which are three etiologies that can cause AKI, often with overlapping pathophysiology 7
Pathophysiological Mechanisms
The pathophysiological mechanisms of AKI can be complex and multifactorial, involving various cellular and molecular processes. For example:
- AKI can result from a sudden loss of excretory kidney function, which can be caused by a range of conditions, including slow deterioration of kidney function or persistent kidney dysfunction 5
- The pathophysiology of AKI can involve cell injury and structural changes within the kidney, which can lead to a longer and more severe disease state with increased morbidity and mortality 7
- Early recognition and reversal of the underlying process are critical to preventing long-term complications of AKI, such as chronic kidney disease and end-stage renal disease 6, 7