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Why ace inhibitors are contraindicated in renal artery stenosis

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"renal artery stenosis" AND "angiotensin-converting enzyme inhibitors"

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renal artery stenosis ACE inhibitors mechanism acute kidney injury guideline

ACE inhibitors reduce formation of angiotensin II. Angiotensin II normally constricts the efferent arteriole, helping maintain glomerular capillary pressure and GFR when renal perfusion is low.
In renal artery stenosis, blood flow into the kidney is already reduced. The kidney becomes dependent on angiotensin II-mediated efferent arteriolar constriction to maintain filtration.
After an ACE inhibitor:
  1. Angiotensin II falls.
  2. The efferent arteriole dilates.
  3. Intraglomerular pressure drops.
  4. GFR falls, potentially causing an abrupt rise in creatinine, oliguria, hyperkalemia, and acute kidney injury.
This is particularly dangerous in:
  • Bilateral significant renal artery stenosis
  • Stenosis of the artery supplying a solitary functioning kidney
  • Volume depletion, heart failure, concurrent diuretics, or NSAID use
In unilateral renal artery stenosis with a normal opposite kidney, an ACE inhibitor is not necessarily absolutely contraindicated. It may be used cautiously, because the unaffected kidney can preserve overall GFR, but renal function and potassium need close monitoring.
Textbook support: Tintinalli lists bilateral renal artery stenosis as an ACE inhibitor contraindication, and nephrology references explain that the risk is loss of pressure-dependent GFR. The NCBI review of renal artery stenosis likewise describes rapid GFR deterioration and AKI risk in bilateral disease or a solitary kidney.
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