Diagnostic Workup and Pre-operative Management for Suspected Pheochromocytoma
For suspected pheochromocytoma, measure plasma free metanephrines or urinary fractionated metanephrines as the initial biochemical test, followed by CT or MRI imaging for localization, and initiate alpha-adrenergic blockade at least 10-14 days before surgery. 1
Diagnostic Workup
Biochemical Confirmation
Plasma free metanephrines achieve the highest sensitivity (97-98%) for diagnosis and should be the first-line biochemical test. 2 If plasma free metanephrines are unavailable, urinary fractionated metanephrines remain the diagnostic test of choice. 2, 1
Very high values (>4 times the upper limit of normal) require no further biochemical testing and confirm the diagnosis. 3
When plasma or urine values are only modestly elevated (less than fourfold elevation), perform a clonidine suppression test to confirm the diagnosis. 4, 2 The test is negative when there is marked reduction of plasma catecholamines after clonidine administration. 2
Avoid preanalytical factors that cause false-positives: discontinue interfering medications, ensure proper patient positioning (supine for 20-30 minutes before blood draw), and avoid stress during collection. 1
Imaging for Localization
CT scanning is the recommended first-line imaging modality for tumor localization. 5, 1 Unenhanced CT showing Hounsfield units <10 strongly suggests a benign tumor, while pheochromocytomas typically appear inhomogeneous with irregular margins. 5
MRI is preferred over CT in patients with metastatic disease, when radiation exposure must be limited (pregnancy, children), or when there is risk of hypertensive crisis from IV contrast. 5, 1
For functional imaging, FDG-PET is superior to MIBG scintigraphy for detecting metastatic pheochromocytoma, particularly in patients with SDHB mutations. 5, 6
Never perform fine needle biopsy of a suspected pheochromocytoma—it is contraindicated due to risk of hypertensive crisis and tumor spillage. 5
Genetic Testing
Genetic testing should be considered in all patients with pheochromocytoma, as approximately 40% of cases are hereditary. 1, 7, 8
Patients with paraganglioma should be tested for SDHx mutations, and those with metastatic disease specifically for SDHB mutations, which carry 31-71% malignancy risk. 6, 1
Testing should be performed by accredited laboratories and guides long-term surveillance strategies. 1
Pre-operative Management
Alpha-Adrenergic Blockade
All patients with functional pheochromocytoma must receive preoperative alpha-blockade for at least 10-14 days before surgery to prevent perioperative hypertensive crises and arrhythmias. 5, 9, 1, 10
Blood pressure targets are <130/80 mmHg supine and systolic >90 mmHg upright. 5
Two alpha-blocker options exist:
- Phenoxybenzamine (non-selective, non-competitive): Start 10 mg twice daily, adjust every 2-4 days. 5 Provides less intraoperative hemodynamic instability but more side effects. 9
- Doxazosin (selective α1-competitive): Start low dose, titrate upward. 5, 11 Has fewer adverse reactions and higher patient tolerability. 11
If target blood pressure is not reached with alpha-blockers alone, add calcium channel blockers (nifedipine slow-release) or metyrosine. 5, 8
Beta-Blockade
Beta-adrenergic receptor blockade should NEVER be started before alpha-blockade to avoid unopposed alpha-stimulation causing hypertensive crisis. 5
Beta-blockers (preferably β1-selective) are indicated only for tachyarrhythmias that develop after adequate alpha-blockade. 5, 10
Volume Optimization
Implement a high-sodium diet and administer 1-2 liters of saline 24 hours prior to surgery to prevent postoperative hypotension. 5, 1
Use compression stockings to reduce orthostatic hypotension risk. 9
Glucocorticoid Management
- In patients with glucocorticoid excess from adrenocortical involvement, administer hydrocortisone 150 mg/day during surgery and postoperatively to prevent adrenal crisis. 5
Glucose Monitoring
- Monitor glucose levels closely postoperatively, as hypoglycemia may occur after reduction of catecholamine levels. 5
Common Pitfalls to Avoid
Do not skip preoperative alpha-blockade even in patients with mild biochemical elevations—hemodynamic instability can still occur. 9, 10
Do not use beta-blockers as monotherapy or before alpha-blockade—this causes paradoxical hypertension. 5
Do not assume normal metanephrines exclude pheochromocytoma in patients with high clinical suspicion—rare non-secreting tumors exist, and imaging should proceed. 5
Do not delay genetic testing—results influence surgical approach, surveillance intensity, and family screening. 1, 8