What is the recommended diagnostic workup for a patient with suspected pheochromocytoma?

Diagnostic Workup for Pheochromocytoma

Initial Biochemical Testing

Plasma free metanephrines (normetanephrine and metanephrine) are the single best first-line screening test, with 96-100% sensitivity and 89-98% specificity, and should be measured in all patients with suspected pheochromocytoma. 1, 2

Optimal Collection Technique

• Collect plasma free metanephrines from an indwelling venous catheter after the patient has been lying supine for 30 minutes to minimize false positives from stress-related catecholamine release 1
• If this ideal collection method is not feasible and results are only marginally elevated (1-2 times upper limit of normal), repeat testing under proper conditions before proceeding 1
• Common antihypertensive medications do not interfere with plasma free metanephrine measurements when using LC-MS/MS analysis 1

Alternative First-Line Test

• 24-hour urinary fractionated metanephrines are an acceptable alternative with 86-97% sensitivity and 86-95% specificity, particularly useful for pediatric patients not yet continent of urine or when plasma collection is impractical 1, 2

Interpretation of Biochemical Results

Markedly Elevated Levels (≥4 times upper limit of normal)

• Proceed directly to imaging to localize the tumor without additional biochemical testing 1
• This degree of elevation is diagnostic for pheochromocytoma/paraganglioma 1

Moderately Elevated Levels (2-4 times upper limit of normal)

• Repeat testing in 2 months 1
• Consider genetic testing for hereditary syndromes, especially in younger patients 1
• Assess for hyperadrenergic symptoms (sustained or intermittent palpitations, tachycardia, diaphoresis, tremors, new-onset hypertension) 1

Marginally Elevated Levels (1-2 times upper limit of normal)

• Repeat testing in 6 months using optimal collection technique (indwelling catheter, 30 minutes supine) 1
• Consider clonidine suppression test if clinical suspicion remains high, which has 96-100% sensitivity and 100% specificity for distinguishing true pheochromocytoma from false positives 1

Common Causes of False Positives

• Obesity, obstructive sleep apnea, and tricyclic antidepressants can cause elevated catecholamine metabolites 1
• False positive elevations are usually <4 times the upper limit of normal 1
• Confirm that interfering agents were avoided prior to testing 1

Confirmatory Testing for Equivocal Results

If plasma free metanephrines show less than fourfold elevation with strong clinical suspicion, perform 24-hour urine collection for fractionated metanephrines and catecholamines. 1, 3

Clonidine Suppression Test

• Reserved for equivocal biochemical results (1-4 times upper limit) when clinical suspicion remains high 1
• Has 100% specificity and 96% sensitivity 1
• Should never replace initial screening or be used when diagnosis is already clear from markedly elevated metanephrines 1

Additional Biomarkers

Measure plasma methoxytyramine when available, as elevated levels indicate higher malignancy risk. 1

• Up to 30% of head/neck paragangliomas produce dopamine, indicated by increases in plasma methoxytyramine 1
• Plasma methoxytyramine >3-fold above upper limit is an indication for functional imaging 1

Anatomical Imaging

First-Line Imaging

MRI is the preferred first-line imaging modality for suspected pheochromocytoma because IV contrast used in CT can precipitate hypertensive crisis. 1, 4

• Only proceed to imaging after biochemical confirmation 1
• If pheochromocytoma has been definitively excluded biochemically, contrast-enhanced CT is acceptable 4

Extended Imaging Protocol

• Obtain cross-sectional imaging of chest, abdomen, and pelvis to detect extra-adrenal paragangliomas and metastases 1
• If initial abdominal imaging is negative but biochemistry is positive, extend imaging to include chest and neck 1

Functional Imaging Indications

Consider functional imaging when any high-risk features are present:

• Tumor size ≥5 cm 1
• Extra-adrenal paraganglioma 1
• SDHB germline mutation 1
• Plasma methoxytyramine >3-fold above upper limit 1

Functional Imaging Modalities

• ¹⁸F-FDG PET is superior to ¹²³I-MIBG scintigraphy for detecting malignant pheochromocytoma, particularly in patients with SDHB mutations 1, 4
• MIBG scintigraphy, DOTA-TATE-PET, and DOPA/Dopamine PET are additional options 4

Genetic Testing

Genetic testing should be offered to all patients with confirmed pheochromocytoma, as approximately 30-35% are hereditary. 1, 4

Indications for Genetic Testing

• Extra-adrenal tumors (paragangliomas) 1
• Bilateral adrenal tumors 1
• Family history of pheochromocytoma or hereditary syndromes (MEN2, VHL, NF1, SDHx mutations) 1
• Young age at presentation 1

High-Risk Genetic Mutations

• SDHB mutations confer up to 70% risk of metastatic disease and mandate immediate referral to endocrinology for intensive lifelong surveillance 1
• SDHD mutations show maternal imprinting—only paternal inheritance causes disease 1

Surveillance Protocols

Pediatric Surveillance

• Begin surveillance at age 2 years for von Hippel-Lindau syndrome 1
• Begin surveillance at age 6-8 years for hereditary paraganglioma/pheochromocytoma (HPP) syndromes 1

Post-Surgical Surveillance

• Repeat biochemical testing 14 days post-surgery to confirm complete resection 1
• Follow-up every 3-4 months for 2-3 years, then every 6 months 1
• Lifelong surveillance is required due to 10-15% recurrence risk and 10-12% malignancy rate 3

Extended Monitoring Criteria

Initiate prolonged lifelong monitoring if any of the following are present:

• PASS (Pheochromocytoma of the Adrenal gland Scaled Score) ≥4 1
• Primary tumor size >5 cm 1
• SDHB gene mutation 1

Critical Safety Precautions

Fine needle biopsy of suspected pheochromocytoma is absolutely contraindicated because it can trigger fatal hypertensive crisis. 1, 4

• Never perform biopsy before biochemical exclusion of pheochromocytoma 1, 4
• Avoid contrast-enhanced CT until pheochromocytoma is definitively excluded 1

Multidisciplinary Management

All patients with suspected or confirmed pheochromocytoma should be presented at a multidisciplinary expert team meeting—including endocrinology, surgery, anesthesiology, and radiology—at the time of initial diagnosis. 1