What is the primary difference in the cause of prerenal AKI versus intrinsic renal AKI?

• A. Prerenal AKI results from post-renal obstruction as the primary cause.
• B. Prerenal AKI is due to reduced renal perfusion, whereas intrinsic AKI is due to tubular/renal parenchymal damage.
• C. Intrinsic AKI is due to decreased renal perfusion from dehydration.
• D. Both types are primarily caused by glomerulonephritis.

Answer: (B)

The key idea is where the injury originates: prerenal AKI is caused by reduced blood flow to the kidneys, while intrinsic AKI involves damage to the kidney tissue itself, particularly the tubules or renal parenchyma. When perfusion to the kidneys drops—due to dehydration, bleeding, heart failure, or shock—the glomeruli receive less blood, lowering the glomerular filtration rate even though the kidney tissue may be structurally intact. If perfusion is restored early, kidney function often recovers fully. Intrinsic AKI results from injury within the kidney, such as ischemic damage to the tubules, nephrotoxic toxins, or inflammatory processes that directly impair tubular function and renal parenchyma. This distinction explains why the primary difference is the site of injury: external perfusion failure versus internal tissue damage.