USMLE Step 3 - Question 39

A 29 year old female with a history of hypertension presents for a routine clinic visit without any physical complaints. Her blood pressure is 180/100 which she admits it has been at home as well. Physical examination reveals normal lung sounds, a regular rhythm with a hyperdynamic apical impulse and an S4 heart sound, an abdominal bruit is heard, no lower extremity edema. Her pulses are 2+ in upper and lower extremities. Her blood pressure medications include lisinopril, amlodipine, atenolol, hydrochlorothiazide, hydralazine, and clonidine which she states she takes regularly. Screening for secondary causes of hypertension thus far has been negative which has included electrolytes, a complete blood count, creatinine, urinary and serum catecholamines, AM cortisol levels, renin/aldosterone levels, thyroid stimulating hormone levels, and a dexamethasone suppression test. Which of the following tests should be ordered next?

A. CT aortogram of the thoracic aorta

B. Magnetic resonance angiography of the renal arteries

C. CT scan of the adrenal glands

D. Serum erythropoeitin levels

When a young female presents with severe hypertension most likely from a secondary cause, fibromuscular dysplasia of the renal arteries should be investigated. This is a "scarring" of the renal arteries that causes severe bilateral renal artery stenosis (RAS) resulting in severe refractory hypertension. The typical angiographic appearance is described as a "string of beads" as shown below:


Renal artery stenting is curative. Remember that bilateral RAS is a common cause of secondary hypertension. It is usually atherosclerotic in nature in patients with other vascular disease (such a coronary artery disease). Starting an ACE inhibitor in a patient with bilateral RAS will cause the creatinine to increase dramatically since angiotensin II usually constricts the efferent arteriole and blocking it will cause the efferent arteriole to dilation and thus less filtration. RAS patients rely more upon that efferent constriction to maintain normal glomerular pressures for filtration. Nevertheless, ACE inhibitors are actually the drug of choice to use to treat hypertension in patients with RAS due to the overactivity of the renin-angiotensin-aldosterone system, as long as their serum creatinine can tolerate it.