WBR0813

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 67-year-old man presents to the physician's office for high blood pressure. Physical examination is remarkable for elevated blood pressures and faintly audible abdominal bruits bilaterally. The physician orders a Doppler ultrasound and the diagnosis of high-grade bilateral atherosclerotic renal artery stenosis is made. The physician decides to initiate anti-hypertensive therapy. Which of following medications should be avoided in this patient?]]
Answer A	AnswerA::Furosemide
Answer A Explanation	AnswerAExp::Diuretics in general are not contraindicated in bilateral renal artery stenosis.
Answer B	AnswerB::Enalapril
Answer B Explanation	AnswerBExp::ACE-inhibitors are contraindicated in bilateral renal artery stenosis.
Answer C	AnswerC::Nifedipine
Answer C Explanation	AnswerCExp::Calcium channel blockers are not contraindicated in bilateral renal artery stenosis.
Answer D	AnswerD::Hydrochlorothiazide
Answer D Explanation	AnswerDExp::Diuretics in general are not contraindicated in bilateral renal artery stenosis.
Answer E	AnswerE::Metoprolol
Answer E Explanation	AnswerEExp::Beta-blockers are not contraindicated in bilateral renal artery stenosis.
Right Answer	RightAnswer::B
Explanation	[[Explanation:: Angiotensin-converting enzyme inhibitors (ACEI) are contraindicated in patients with bilateral renal artery stenosis because they might cause acute kidney injury. In high-grade bilateral renal artery stenosis, the glomerular filtration rate (GFR) depends mostly on the action of angiotensin II (ANGII) depletion of extracellular fluid volume. ANGII regulates renal vascular resistance by activation of renin from the juxtaglomerular cells and the sympathetic nervous system to maintain renal blood flow (RBF) and GFR. It is important to remember that ANGII has a preferential vasoconstrictive role on the efferent arteriole (post-glomerulus) than the afferent arteriole (pre-glomerulus); this mechanism is normally advantageous because it maintains GFR when perfusion pressure decreases. The use of ACE-I and losing the capacity of ANGII to maintain GFR in patients whose renal perfusion is highly dependent on the action of ANGII, such as in bilateral renal artery stenosis or advanced renal disease, will lead to reduced GFR and renal impairment. Accordingly, ACE-I are contraindicated in bilateral renal artery stenosis. The same applies to angiotensin receptor blockers (ARBs) that have a similar effect. Educational Objective: ACE inhibitors are contraindicated in bilateral renal artery stenosis. References: Schoolwerth AC, Sica DA, Ballermann BJ, et al. Renal considerations in angiotensin converting enzyme inhibitor therapy. A statement for healthcare professionals from the council on the kidney in cardiovascular disease and the council on high blood pressure research of the American Heart Association. Circulation. 2001; 104:1985-1991.]]
Approved	Approved::Yes
Keyword	WBRKeyword::ACE inhibitor, WBRKeyword::Angiotensin converting enzyme, WBRKeyword::Bilateral renal artery stenosis, WBRKeyword::RAS, WBRKeyword::Hypertension, WBRKeyword::Bruit, WBRKeyword::ARB, WBRKeyword::Angiotensin receptor blocker
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