A 57-year-old man comes to the office for a follow-up visit two weeks after an emergency department (ED) visit during which a sudden rise in his blood pressure to 190/110 mmHg was noted. He has had essential hypertension for approximately twelve years, optimally controlled by hydrochlorothiazide and amlodipine, until this past month when his blood pressure readings were consistently higher than before. He has been extremely compliant with his diet and medications. He does not have any other medical problems. He has smoked one pack of cigarettes daily for 20 years. He denies any recent use of alcohol or illicit drugs. In the office, his blood pressure is 160/94 mmHg in the right arm and 162/96 mmHg in the left arm. His BMI is 28 kg/m². Cardiovascular examination reveals regular heart sounds and a 1/6 systolic murmur at the apex. There is a faint right-sided carotid bruit. Left-sided popliteal and posterior tibialis pulses are barely palpable. His serum creatinine level is 1.1 mg/dL. Which of the following is most helpful in establishing this patient's diagnosis?

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Explanation: This patient's presentation of severe hypertension which is resistant to two medications and has acutely worsened from a previously stable state is suspicious for a secondary cause of hypertension. An age of onset before 30 years or malignant hypertension would also raise suspicion for secondary hypertension. Renovascular hypertension is the most common secondary cause of hypertension, although it is still far less common than essential hypertension. Renovascular disease would be a possibility in this patient given the high likelihood of atherosclerotic disease in the right carotid artery and left lower extremity vasculature based on the physical exam. Other clues that might suggest renovascular hypertension include elevated creatinine, unilateral renal atrophy, recurrent flash pulmonary edema, and an abdominal bruit on physical exam. In patients such as this with moderate risk of renovascular hypertension, imaging evaluation with MRA, CTA, or Doppler Ultrasound should be performed. (Choice A) Captopril renal scintigraphy can be considered for the evaluation of renovascular hypertension, but is not one of the preferred modalities according to the ACC/AHA guidelines. The test is not currently favored because of a high prevalence of asymmetric renal blood flow in the general population that can confuse results, as well as a relatively high false negative rate. (Choice B) An atrophic kidney or delayed contrast excretion on an intravenous pyelogram can be suggestive of renal ischemia, but these findings are relatively unreliable and thus intravenous pyelography should not be used as a screening modality for renovascular hypertension. (Choice C) A low dose dexamethasone suppression test is used to diagnose Cushing's disease. While Cushing's disease can be a secondary cause of hypertension, this patient has no obesity, muscle weakness, hyperpigmentation, bruising, or other Cushingoid features to suggest the diagnosis. (Choice E) Urine metanephrines are a screening test for pheochromocytoma, which is a less likely cause of secondary hypertension in this patient given the absence of episodic headache, sweating, and tachycardia accompanying his hypertension. Educational objective: Secondary causes of hypertension should be suspected in patients with severe hypertension, resistance to multiple medications, worsening from a previously stable baseline, or young age of onset. Renovascular hypertension is the most common secondary cause of hypertension and should be suspected in patients with renal atrophy, atherosclerotic disease elsewhere in the body, or renal failure. References: Imaging modalities for renal artery stenosis in suspected renovascular hypertension: prospective intraindividual comparison of color Doppler US, CT angiography, GD-enhanced MR angiography, and digital substraction angiography. (http://www.ncbi.nlm.nih.gov/pubmed/17497443) Radiologic evaluation of suspected renovascular hypertension. (http://www.ncbi.nlm.nih.gov/pubmed/19621837)

A 57-Year-Old Man Comes to the Office for a Follow-Up