ACE inhibitors carry a risk of renal failure in which condition?

• A. Bilateral renal artery stenosis or stenosis in the artery to a single remaining kidney
• B. Chronic kidney disease stage 1
• C. Acute glomerulonephritis
• D. Urinary tract infection

Answer: (A)

ACE inhibitors can precipitate acute kidney injury when renal perfusion depends on angiotensin II to maintain glomerular filtration. In renal artery stenosis, especially when both kidneys are affected or there is a solitary functioning kidney, the efferent arteriole remains constricted largely due to angiotensin II to preserve GFR despite reduced blood flow. Blocking the formation of angiotensin II with an ACE inhibitor removes this compensatory constriction, causing dilation of the efferent arteriole, a drop in intraglomerular pressure, and a reduction in GFR. The result can be acute renal failure.

In contrast, conditions like early chronic kidney disease, glomerulonephritis, or a urinary tract infection do not rely on angiotensin II–mediated efferent arteriolar constriction to maintain GFR in the same way, so the risk of ACE-inhibitor–induced renal failure is not inherently driven by those scenarios.