Examkin

Question

Difficulty: MediumDiagnostic Workup and Test Sequencing

A 42-year-old woman is referred to the endocrinology clinic due to treatment-resistant hypertension. She currently takes amlodipine, lisinopril, and hydrochlorothiazide at maximal tolerated doses, but her home blood pressure readings consistently range from 160/95 to 175/105 mmHg. Over the past year, she has also experienced episodic, severe, throbbing headaches accompanied by palpitations and profuse sweating. Her vital signs today show a blood pressure of 168/102 mmHg and a heart rate of 105/min. Physical examination is unremarkable, with no abdominal bruits or striae. Because of her classic symptoms, measurement of plasma free metanephrines is performed, revealing levels that are more than four times the upper limit of normal. Which of the following is the most appropriate next step in this patient's diagnostic workup?

  1. Computed tomography of the abdomen and pelvisAnswer
  2. B
    Metaiodobenzylguanidine (MIBG) scintigraphy
  3. C
    Fine-needle aspiration biopsy of the adrenal glands
  4. D
    Clonidine suppression test
  5. E
    Renal artery duplex ultrasonography

Answer

Computed tomography of the abdomen and pelvis
The correct sequence for diagnosing a pheochromocytoma involves establishing clinical suspicion, obtaining biochemical confirmation, and then performing anatomical localization. This patient has definitively positive biochemical testing (plasma free metanephrines >4 times normal). The next required step is to locate the tumor anatomically. Because approximately 90% of pheochromocytomas arise in the adrenal medulla and most extra-adrenal paragangliomas occur in the abdomen or pelvis, a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the abdomen and pelvis is the most appropriate initial localizing study.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has treatment-resistant hypertension combined with the classic triad of episodic headaches, sweating, and palpitations, which is highly suspicious for a pheochromocytoma.
Identifying the clinical syndrome guides the biochemical evaluation.
2
Evaluate the results of the initial diagnostic testing.
Plasma free metanephrines are greater than four times the upper limit of normal, providing definitive biochemical confirmation of a catecholamine-secreting tumor.
The diagnostic pathway for endocrine tumors requires biochemical proof of hormone excess before attempting to locate the source.
3
Determine the appropriate sequential step in the workup.
Because the biochemical diagnosis is secure, the next step is anatomical localization using computed tomography (CT) or magnetic resonance imaging (MRI) of the abdomen and pelvis.
Approximately 90% of pheochromocytomas are located in the adrenal glands, and almost all others are intra-abdominal. Cross-sectional imaging is the most sensitive initial localizing test.

Key Concept

In the evaluation of suspected pheochromocytoma, definitive biochemical confirmation (via metanephrines) must be followed immediately by anatomical localization using cross-sectional imaging (CT or MRI) of the abdomen and pelvis.
Rate this question

Topics

Diagnostic Workup and Test Sequencing

More questions from this topic