A 20-year-old woman presents to the physician with a high blood pressure reading of 160/90 mm Hg, initially noted three days ago during a physical examination before starting a volunteer activity at a hospital. Her past medical history is negative, and she does not take any medications. She does not drink alcohol, smoke cigarettes, or use illicit substances. At this visit, her blood pressure is 160/85 mm Hg, and her other vital signs are within normal limits. Her body mass index (BMI) is 25. On physical examination, a right carotid bruit is auscultated. An electrocardiogram is normal. Blood tests reveal a normal chemistry panel, CBC, TSH, and lipid panel. Plasma renin activity is high, aldosterone level is high, and aldosterone-renin ratio is normal.
Which of the following is the most appropriate next step in the evaluation of this patient?
E) Computed tomography angiogram of the abdomen
This patient's carotid bruit and elevated blood pressure at a young age suggest fibromuscular dysplasia (FMD). FMD is a nonatherosclerotic, noninflammatory disease affecting the arterial walls, leading to stenosis, aneurysms, and dissections. It typically affects women under the age of 50 and commonly involves the renal and internal carotid arteries. Clinical features include severe or resistant hypertension, particularly in young women, onset of hypertension before age 35, sudden increases in blood pressure, and an increase in creatinine levels after starting angiotensin converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation without a significant effect on blood pressure. Additional manifestations may include cerebrovascular symptoms such as transient ischemic attacks, strokes, and nonspecific symptoms like headaches and dizziness.
In patients with suspected FMD, the diagnosis is confirmed by diagnostic imaging that reveals consistent findings. A noninvasive imaging test such as CTA is usually performed first. CTA has strong diagnostic accuracy for FMD of the main renal arteries. Invasive angiography is performed in patients if there is a high clinical suspicion of FMD, and treatment with revascularization is planned if a stenosis is found. A negative angiogram excludes a diagnosis of FMD in the vascular bed that was imaged. Of note, though CTA of the abdomen is used to diagnose FMD in the patient, she also should have imaging of her carotid arteries to evaluate the bruit heard on physical examination.
Answer choice A: 24-hour urine cortisol, is incorrect. 24-hour urine cortisol is used to diagnose Cushing syndrome, which is not suggested by the patient's clinical presentation and findings.
Answer choice B: Adrenal venous sampling, is incorrect. Adrenal venous sampling is used to differentiate between unilateral and bilateral adrenal disease in patients with primary hyperaldosteronism, which is not indicated here as the aldosterone-renin ratio is normal.
Answer choice C: Check blood pressure again, is incorrect. Rechecking the blood pressure is important, but given the presence of a carotid bruit and elevated plasma renin and aldosterone activity, further diagnostic imaging is warranted rather than simply rechecking blood pressure.
Answer choice D: Check plasma fractionated metanephrines, is incorrect. Plasma fractionated metanephrines are used to diagnose pheochromocytoma with a high pretest probability, but pheochromocytoma is not the most likely diagnosis based on the patient's symptoms or clinical findings.
Key Learning Point
Fibromuscular dysplasia (FMD) is suggested by early-onset hypertension, a carotid bruit, and high plasma renin and aldosterone levels. It often affects young women, involving renal and internal carotid arteries. Approximately 75-80% of patients with FMD have involvement of the renal arteriesthe time while 75% have involvement of the extracranial cerebrovascular arteries (carotid and vertebral arteries). Approximately 2/3 of patients have multiple arteries involved. Among adults, FMD is more common among females. CTA of the abdomen is the preferred diagnostic test.
