From the Guidelines
The initial workup for pheochromocytoma involves biochemical testing to detect excess catecholamines or their metabolites, with plasma free metanephrines being the best screening test, carrying a 99% sensitivity and an 89% specificity 1. The initial workup for pheochromocytoma is crucial in diagnosing this rare but potentially life-threatening condition.
- Biochemical testing is the first step, which includes measuring circulating catecholamine metabolites such as normetanephrine and metanephrine.
- The screening test of choice is plasma free metanephrines, which has a high sensitivity and specificity 1.
- If biochemical testing is positive, imaging studies are then performed to localize the tumor, with CT scan with contrast of the abdomen and pelvis being the first imaging study, as most pheochromocytomas occur in the adrenal glands 1.
- MRI is an alternative for patients who cannot receive contrast, and functional imaging with 123I-MIBG scintigraphy or PET scanning may be necessary for suspected extra-adrenal tumors or metastatic disease 1.
- Genetic testing should also be considered, as approximately 40% of pheochromocytomas are associated with hereditary syndromes such as MEN2, von Hippel-Lindau disease, neurofibromatosis type 1, and SDH mutations 1. The workup should be conducted while monitoring blood pressure carefully, as these tumors can cause dangerous hypertensive episodes 1.
- It is essential to consider the diagnosis of pheochromocytoma in anyone referred for resistant hypertension, given the high morbidity and mortality of not treating these tumors 1.
- The recent Endocrine Society guideline recommends starting with computed tomography, with magnetic resonance imaging as an alternative, and metaiodobenzylguanidine scanning to further evaluate suspected metastatic disease 1.
From the Research
Initial Workup for Pheochromocytoma
The initial workup for pheochromocytoma involves biochemical testing to establish the diagnosis, followed by radiological imaging to localize the tumor. The key steps in the initial workup are:
- Biochemical testing: measuring plasma free metanephrines and urinary fractionated metanephrines 2, 3, 4, 5
- Radiological imaging: computed tomography (CT) or magnetic resonance imaging (MRI) to localize the tumor 2, 3
Biochemical Testing
Biochemical testing is the first step in diagnosing pheochromocytoma. The tests used include:
- Plasma free metanephrines: this test is highly sensitive and specific for pheochromocytoma 2, 5
- Urinary fractionated metanephrines: this test is also highly sensitive and specific for pheochromocytoma 2, 3, 4
- Urinary free metanephrines: this test has been shown to be a reliable method for diagnosing pheochromocytoma, especially in Asian populations 4
Radiological Imaging
Once the biochemical diagnosis is established, radiological imaging is used to localize the tumor. The imaging tests used include:
- Computed tomography (CT): this test is highly sensitive for localizing pheochromocytoma 2, 3
- Magnetic resonance imaging (MRI): this test is also highly sensitive for localizing pheochromocytoma 2, 3
- Scintigraphy with (123)I-metaiodobenzylguanidine (MIBG): this test is highly specific for pheochromocytoma, but less sensitive than CT or MRI 2, 3
Additional Testing
Additional testing may be necessary in some cases, including: