NBME 21 Left renal artery atherosclerosis (NBME Answers)

NBME 21 Answers

nbme21/Block 3/Question#12 (reveal difficulty score)
A 55-year-old man with hypertension comes to ...
Left renal artery atherosclerosis 🔍 / 📺 / 🌳 / 📖
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submitted by ∗pg32(218)

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NBME/Uworld love to test renal artery stenosis in the setting of hypertensive urgency/emergency. Just because this has been done so many times, you can basically get the right answer from the first half of the question. Pt with end organ issues (headache, confusion) and really high BP (I know it isn't 180/120, but it is really high). So this guy basically has hypertensive emergency. I'm already thinking it's renal artery stenosis. Next sentence? A bruit over the left abdomen. Bingo. Renal artery stenosis, most often caused by atherosclerosis in older men (as compared to fibromuscular dysplasia in younger women).

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lovebug He is heavy smoker but, No weight loss, No cachexia -> so can be R/O Left renal cell carcinoma. is it right? +

lovebug Renovascular ds. FA2019, pg 592. +

misrao and no hematuria so r/o RCC +

realnorthomfs FA2020, pg 604 +

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submitted by necantoramericanus(3)

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Im not really sure but I think the point is that with the captopril radionuclide scan there is a delay in function of the kidney. What they wanted us to remember here is that when you give a " A pril" to a patient with Renal artery atherosclerosis the renal function worsens because there is constriction of the efferent arteriole

FA 2018 - 567

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kevin efferent dilates with an ACE-I due to loss of angiotensin mediated vasoconstriction +

skonys This is an aside but they love testing Renal Artery Stenosis in the context of ACE Inhibitors because it's a good physiology tie-in. First, it helps to know that Angiotensin II's entire role in the kidney/the reason it evolved, is to maintain GFR in the setting of low kidney perfusion (hypovolemic shock). It preferentially vasoconstricts the eff arteriole, increasing the pressure just anterior to the occlusion, thus forcing filtrate into bowmans capsule despite there being less blood volume running through the artery. In Bilateral Renal Artery Stenosis, maintenance of the GFR is completely reliant on AngII vasoconstriction of the efferent arteriole. If you give someone an ACE inhibitor, you decrease AngII and vasodilate the efferent arteriole. The force maintaining the GFR is gone, precipitating pre-renal azotemia. That's why people with suspected Renal AS need to have their CK monitored closely because it will increase after administrating and ACE Inhibitor. +

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submitted by ∗usmleuser007(464)

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Just realized that renal cell carcinoma isn't the correct answer b/c it invaded the venous circulation and not the arterial. BP may not be affected as much. if RCC were the answer then then there would have been edema present and/or renal HTN.

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sympathetikey Also, just thinking out loud, in the case of RCC, it's the kidney tissue that's dysplastic & moving, so technically the renal artery itself isn't dysplastic, right? +

paperbackwriter @usmleuser007 very good point regarding the venous vs arterial circulation that I neglected to consider! +

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submitted by ∗rainlad(33)

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How do we explain the bruit in this case? Also why isn't it left artery aneurysm? That seems like it would better explain the bruit

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gdupgrant The bruit is basically just turbulent flow, which is most commonly caused by artery narrowing. I was just reading https://emedicine.medscape.com/article/463015-clinical on renal artery aneurysm and it looks like most of the hypertension is actually related to a pre aneurysm stenosis, so i think stenosis is the "better" answer, esp. since the pt has like every risk factor for stenosis. To be honest I had not ever really thought about RAA for this case because bruit over RA has been drilled into my head as renal artery stenosis, but i apprecaite seeing how this is a super reasonable answer - just the stenosis is "more likely" +2

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submitted by ∗usmleuser007(464)

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For RCC: (As per UWORLD)

Symmetric bilateral lower extremity pitting edema and tortuous abdominal veins are concerning for an inferior vena cava (IVC) obstruction, which, in the setting of a left-sided flank mass, suggests renal cell carcinoma (RCC) with extension into the IVC. RCC accounts for >90% of all malignancies arising in the kidney and is highly associated with smoking. Patients with RCC classically have a triad of flank pain, palpable mass, and hematuria, although many remain asymptomatic until the disease is advanced. RCC is a highly vascular tumor that invades the renal vein in up to 25% of cases. IVC obstruction can occur due to intraluminal extension and thrombus formation, rather than mass effect from the tumor itself.

The obstruction can occur acutely or gradually over time. In chronic cases, collateral venous circulation may develop based on the site of the obstruction. Prominent abdominal wall collateral veins, as in this patient, suggest obstruction of the upper segment of the IVC.

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nor16 high blood pressure, i.e. Hypertension, risk factors for atheroscl., bruit !!! over left abdomen, secondary art. Hypertension. they always want the renal artery stenosis (like vWF in coag. disorders...) +

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submitted by ∗jackie_chan(34)

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I approached this question because man with rather extreme HTN and abdominal bruit is quite often renal stenosis

ALso captopril renal radionuclide scan's function is literally to assess renal stenosis (looked it up, but i did not know that when i answered)

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