Pre-renal acute kidney injury may be worsened by which combination?

Pre-renal acute kidney injury may be worsened by which combination?

• A. Hypovolemia alone
• B. Afferent arteriole constriction (NSAIDs, IV contrast) plus efferent arteriole dilation (ACE inhibitors/ARBs)
• C. Intrinsic tubular injury
• D. Ureteral obstruction

Answer: (B)

In prerenal AKI the problem is reduced blood flow to the kidneys, so anything that lowers inflow or the forces driving filtration can make things worse. Afferent arteriole constriction, like from NSAIDs or IV contrast, cuts blood entering the glomerulus, lowering the hydrostatic pressure that drives filtration. Efferent arteriole dilation, as seen with ACE inhibitors or ARBs, lowers the pressure inside the glomerulus from the outflow side, further reducing the filtration pressure. When these two effects occur together—inflow is restricted and outflow pressure is eased—the net glomerular filtration pressure falls more than with either change alone. That combination particularly worsens pre-renal AKI, especially in states of reduced renal perfusion such as dehydration or hypovolemia. The other scenarios either cause prerenal injury via a single mechanism or represent different types of kidney injury (intrinsic tubular injury or post-renal obstruction), so they don’t produce this same synergistic drop in filtration pressure.

In prerenal AKI the problem is reduced blood flow to the kidneys, so anything that lowers inflow or the forces driving filtration can make things worse. Afferent arteriole constriction, like from NSAIDs or IV contrast, cuts blood entering the glomerulus, lowering the hydrostatic pressure that drives filtration. Efferent arteriole dilation, as seen with ACE inhibitors or ARBs, lowers the pressure inside the glomerulus from the outflow side, further reducing the filtration pressure.

When these two effects occur together—inflow is restricted and outflow pressure is eased—the net glomerular filtration pressure falls more than with either change alone. That combination particularly worsens pre-renal AKI, especially in states of reduced renal perfusion such as dehydration or hypovolemia.

The other scenarios either cause prerenal injury via a single mechanism or represent different types of kidney injury (intrinsic tubular injury or post-renal obstruction), so they don’t produce this same synergistic drop in filtration pressure.