In bilateral renal artery stenosis, administration of an ACE inhibitor typically leads to which of the following?

• A. Increase in blood pressure
• B. Decrease in blood pressure
• C. No change in blood pressure
• D. Immediate normalization of creatinine

Answer: (D)

In bilateral renal artery stenosis the kidney relies on angiotensin II to maintain glomerular filtration pressure. Angiotensin II constricts the efferent arteriole, preserving filtration even when renal perfusion is reduced. An ACE inhibitor blocks angiotensin II formation, leading to dilation of the efferent arteriole. This lowers intraglomerular pressure and GFR, typically causing an rise in serum creatinine rather than any improvement. So, instead of normalizing creatinine immediately, ACE inhibitors in this setting can precipitate a decline in kidney function. Clinically, this is why such patients require careful monitoring of creatinine after starting therapy and why ACE inhibitors are used with caution if bilateral RAS is suspected.