A 29-year-old man comes to the emergency department complaining of palpitations, sweating, and severe headache. His symptoms resolve spontaneously by the time he is evaluated. He has had at least 2 similar episodes during the past 2 months. The patient’s family history is unremarkable. He does not use tobacco, alcohol, or illicit drugs. His primary care provider saw him after the first episode and prescribed an anxiolytic medication. However, the patient felt drowsy at his job and stopped the medication. Physical examination shows a thin man who appears anxious and diaphoretic. The thyroid is normal to palpation without any obvious nodules. His temperature is 36.7 C (98 F), blood pressure is 126/84 mm Hg, pulse is 86/min, and respirations are 16/min. During his prior emergency department visit for an identical episode, his blood pressure was 150 /100 mm Hg and pulse was 120 /min. The laboratory results at that time showed normal thyroid function tests.
Item 1 of 3
Which of the following is the most appropriate next step in management?
- A. Measure 24-hour fractionated urinary metanephrines and catecholamines [76%]
- B. Measure 24-hour urinaryvanillylmandelic acid excretion [1 6%]
- C. Measure blood pressure in the office after 2 weeks [3%]
- D. Start a beta blocker [3%]
- E. Start an alpha blocker [2%]
This patient’s episodic symptoms and hypertension are concerning for pheochromocytoma. The classic triad for pheochromocytoma includes episodic headache, sweating, and tachycardia. However, most patients may not have all 3 findings. Other findings can include orthostatic hypotension, blurry vision, and weight loss.
Measurement of 24-hour fractionated urinary metanephrines and catecholamine levels is one of the preferred screening tests for the biochemical diagnosis of pheochromocytoma. Some experts prefer measuring plasma fractionated metanephrines as the initial screening test, which has high sensitivity but lower specificity than the 24-hour urine test. Urine levels of catecholamines, and metanephrines and plasma fractionated metanephrines can be affected by a number of drugs (eg, tricyclic antidepressants, over-the-counter decongestants), which should be stopped for 2 weeks before testing. Twenty-four-hour urinary vanillylmandelic acid excretion has a much lower sensitivity and specificity compared with 24-hour urinary fractionated metanephrine (Choice B).
(Choice D) Beta-adrenergic receptor blockade before alpha-adrenergic receptor blockade may worsen hypertension in pheochromocytoma as unopposed alpha-adrenergic activity may cause vasoconstriction.
(Choice E) Alpha blockers can falsely elevate catecholamine and metanephrines, which can interfere with correct interpretation of these test results. As a result, alpha blockers are started after confirming biochemical diagnosis of pheochromocytoma.
Educational objective: Screening for pheochromocytoma should be considered in patients with episodic symptoms (headaches, diaphoresis, and tachycardia), early age-onset or refractory hypertension, and paroxysmal hypertension. A biochemical diagnosis of pheochromocytoma is typically made by measuring plasma free metanephrine levels or a 24-hour urine collection for measurement of catecholamine and me tanephrine.