In renal physiology, massive hemorrhage most commonly causes which type of acute kidney injury (AKI)?

• A. Intrinsic AKI due to acute interstitial nephritis
• B. Postrenal AKI due to bilateral ureteral obstruction
• C. Prerenal AKI due to decreased renal perfusion (ischemia from hypovolemia)
• D. Intrinsic AKI due to rapidly progressive glomerulonephritis

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the types of acute kidney injury (AKI). AKI is generally classified into three categories: prerenal, intrinsic (intrarenal), and postrenal. Prerenal AKI results from decreased blood flow to the kidneys, intrinsic AKI involves direct damage to the kidney tissue, and postrenal AKI is caused by obstruction of urine flow.
2. Step 2: Analyze the cause of massive hemorrhage. Massive hemorrhage leads to significant blood loss, which reduces the circulating blood volume (hypovolemia). This decrease in blood volume results in reduced renal perfusion, meaning less blood reaches the kidneys.
3. Step 3: Connect hypovolemia to kidney injury type. Since the primary problem is decreased blood flow to the kidneys due to low blood volume, this situation fits the definition of prerenal AKI, where ischemia (lack of oxygen) occurs because of insufficient perfusion.
4. Step 4: Differentiate from other AKI types. Intrinsic AKI such as acute interstitial nephritis or rapidly progressive glomerulonephritis involves direct damage to kidney tissues, which is not the immediate effect of hemorrhage. Postrenal AKI involves obstruction, which is unrelated to blood loss.
5. Step 5: Conclude that massive hemorrhage most commonly causes prerenal AKI due to decreased renal perfusion from hypovolemia, as this is the direct physiological consequence of significant blood loss.