From the Guidelines
The diagnostic workup for pheochromocytoma should begin with biochemical testing, specifically measuring plasma free metanephrines or 24-hour urinary fractionated metanephrines and catecholamines, as recommended by the most recent guidelines 1.
Biochemical Testing
The initial screening for pheochromocytoma involves detecting excess catecholamines or their metabolites. The tests of choice include:
- Plasma free metanephrines
- 24-hour urinary fractionated metanephrines and catecholamines These tests have high sensitivity and are crucial for identifying patients with pheochromocytoma.
Imaging Studies
If biochemical tests are positive, imaging studies should be conducted to localize the tumor. The recommended imaging modalities are:
- CT scan with contrast of the abdomen and pelvis as the first-line imaging modality
- MRI as an alternative
- Functional imaging with 123I-MIBG scintigraphy or PET scanning with specific tracers like 18F-FDOPA for more specific localization
Genetic Testing
Genetic testing should be considered in all patients with pheochromocytoma, particularly those with a family history, bilateral tumors, or young age of onset, as up to 40% of cases are associated with hereditary syndromes 1.
Preoperative Management
Before surgical removal, patients require preoperative medical management with:
- Alpha-adrenergic blockade (typically phenoxybenzamine 10-30 mg twice daily or doxazosin 2-8 mg daily) for 1-2 weeks
- Beta-blockade (propranolol 20-40 mg three times daily or metoprolol 25-50 mg twice daily) if needed for tachycardia This preparation is crucial to prevent hypertensive crisis during surgery, as pheochromocytomas secrete catecholamines that cause episodic or sustained hypertension, headaches, sweating, and palpitations.
The most recent and highest quality study 1 provides the basis for these recommendations, prioritizing morbidity, mortality, and quality of life as the outcome.
From the Research
Diagnostic Workup for Pheochromocytoma
The diagnostic workup for pheochromocytoma involves several steps, including:
- Biochemical testing to confirm the presence of a catecholamine-secreting tumor 2
- Radiological imaging tests to locate the tumor 2
- Specific functional imaging tests to confirm the diagnosis 2
Biochemical Testing
Biochemical testing for pheochromocytoma typically involves measuring:
- Plasma free metanephrines 2, 3, 4, 5, 6
- Urinary fractionated metanephrines 2, 3, 4, 6
- Urinary catecholamines 3, 5 The most sensitive test for diagnosing pheochromocytoma is plasma free metanephrines, with a sensitivity of 99% 4 and 98% 6 The specificity of plasma free metanephrines is also high, ranging from 89% 4 to 92% 6
Radiological Imaging Tests
Radiological imaging tests used to locate pheochromocytomas include:
- Computed tomography (CT) 2
- Magnetic resonance imaging (MRI) 2 These tests are used to locate the tumor and determine its size and location
Specific Functional Imaging Tests
Specific functional imaging tests used to confirm the diagnosis of pheochromocytoma include:
- Scintigraphy with (123)I-metaiodobenzylguanidine (MIBG) 2
- Scintigraphy with (131)I-MIBG 2
- Positron emission tomography (PET) with (18)F-F-fluorodopamine (F-DA) 2 These tests are used to confirm the presence of a catecholamine-secreting tumor and to determine its location and size
Comparison of Diagnostic Tests
Studies have compared the effectiveness of different diagnostic tests for pheochromocytoma, including:
- Plasma free metanephrines vs. urinary catecholamines 5
- Plasma free metanephrines vs. urinary fractionated metanephrines 3, 4
- Urinary catecholamines vs. urinary fractionated metanephrines 3 The results of these studies suggest that plasma free metanephrines are the most sensitive test for diagnosing pheochromocytoma, while urinary fractionated metanephrines are also highly sensitive and specific 3, 4