A 38-year-old woman presents with BP 162/108 mmHg on two separate visits over 2 weeks. She reports episodic severe headaches, profuse sweating, and palpitations lasting 20–30 minutes, occurring 2–3 times weekly. She is not on any antihypertensive medication. Physical examination reveals no abnormalities. Serum potassium is 3.2 mEq/L (normal 3.5–5.0). What is the most appropriate next step in management?

Explanation

## Clinical Presentation Suggestive of Secondary Hypertension This patient presents with classic features of **pheochromocytoma**: - Episodic severe hypertension with paroxysmal symptoms - Triad of headache, sweating, and palpitations - **Hypokalemia** (3.2 mEq/L) — a key clue suggesting catecholamine excess and secondary hypertension - Young age with no prior hypertension history - Symptoms lasting 20–30 minutes (typical duration of catecholamine surge) ## Diagnostic Approach **Key Point:** Hypokalemia in a young hypertensive patient with paroxysmal symptoms is a red flag for secondary hypertension, particularly pheochromocytoma. Biochemical confirmation must precede imaging. **High-Yield:** The gold-standard screening test for pheochromocytoma is **24-hour urine metanephrines** or **plasma free metanephrines**. Both have >95% sensitivity and specificity. Plasma free metanephrines are preferred in many centers due to higher sensitivity and convenience (single blood draw). ## Why This Is the Next Step 1. **Biochemical confirmation first** — imaging (CT/MRI) should only be performed if biochemical tests are positive 2. **High pre-test probability** — the clinical presentation is highly suggestive 3. **Hypokalemia is a clue** — catecholamine excess causes hypokalemia via β~2~-mediated shift of K^+^ intracellularly ## Why Not Other Options? | Option | Reason for Rejection | |--------|---------------------| | Start amlodipine monotherapy | Treating without investigating secondary hypertension in a young patient with hypokalemia and paroxysmal symptoms is inappropriate; would delay diagnosis and risk hypertensive crisis | | Renal artery duplex | While renovascular hypertension is a cause of secondary HTN, it does NOT cause hypokalemia or paroxysmal symptoms; pheochromocytoma is far more likely here | | Start dual therapy (lisinopril + HCTZ) | Initiating antihypertensives without ruling out pheochromocytoma is dangerous; unopposed α-blockade can precipitate a hypertensive crisis | **Clinical Pearl:** **Never start antihypertensives in suspected pheochromocytoma without first confirming the diagnosis biochemically.** Unopposed β-blockade or vasodilators without α-blockade can trigger a catecholamine surge and life-threatening hypertensive emergency. **Mnemonic — 5 P's of Pheochromocytoma:** Pressure (hypertension), Pain (headache), Perspiration (sweating), Palpitations, Perspicacity (anxiety). This patient has 4 of 5. **Warning:** Hypokalemia + paroxysmal hypertension = think pheochromocytoma first, not primary hypertension. [cite:Harrison 21e Ch 297]