Pheochromocytoma

Pheo Basics - Adrenal Overdrive

• Rare catecholamine-secreting neuroendocrine tumor.
• Arises from chromaffin cells of the sympatho-adrenal system.
• Origin:
  • Adrenal medulla (~80-85% of pheochromocytomas).
  • Extra-adrenal paraganglia (~15-20%, termed paragangliomas); commonest is organ of Zuckerkandl.
• 📌 Rule of 10s (classic, but some figures vary with modern genetics):
  • 10% bilateral adrenal
  • 10% extra-adrenal
  • 10% malignant
  • 10% pediatric
  • 10% familial (now known to be higher, up to 30-40% with genetic testing)
  • 10% asymptomatic (often an incidentaloma)

⭐ Pheochromocytomas are a classic cause of surgically correctable hypertension.

Symptom Storm - Pressure Cooker

• Classic Triad (PHE): 📌
  • Palpitations
  • Headache (often throbbing)
  • Episodic sweating (diaphoresis)
• Hypertension: Often paroxysmal (sudden attacks), can be sustained.
  • Systolic BP can exceed 200-300 mmHg.
  • Diastolic BP can exceed 130-180 mmHg.
• Other symptoms: Anxiety, tremors, pallor, chest/abdominal pain, nausea, vomiting, fatigue, weight loss.
• Triggers: Can be spontaneous or precipitated by stress, anesthesia, surgery, certain foods (tyramine-rich), or medications (e.g., beta-blockers without alpha-blockade, MAOIs).

⭐ Catecholamine Cardiomyopathy: Reversible left ventricular dysfunction can occur due to excessive catecholamine stimulation, mimicking dilated cardiomyopathy or Takotsubo cardiomyopathy (stress-induced).

Detective Work - Finding Pheo

• Biochemical Confirmation First: Crucial before imaging.

  • Key Diagnostic Tests:

    Test	Sensitivity	Specificity	Key Point
    Plasma free metanephrines (PFM)	>95%	~85-89%	Highest sensitivity; preferred test
    Urinary fractionated metanephrines	~90-97%	~90-95%	Confirmatory; good alternative
    24-hr Urinary VMA	Lower (~60%)	Lower (~90%)	Less sensitive/specific

  • Diagnostic Threshold: Levels >2-3 times upper limit of normal (ULN).

  • 📌 Mnemonic: "Rule of 10s for Pheo, but test with Plasma Metanephrines".

• Imaging (Post-Biochemical Confirmation):
  • Anatomical: CT abdomen/pelvis (initial); MRI (children, pregnancy, contrast allergy).
  • Functional: ¹²³I-MIBG scintigraphy; ⁶⁸Ga-DOTATATE PET/CT (metastatic/extra-adrenal disease).

⭐ Plasma free metanephrines (PFM) are the most sensitive initial biochemical test for pheochromocytoma and paraganglioma.

Taming the Tumor - Surgical Gameplan

Pre-operative Goals: Achieve BP <130/80 mmHg (seated), SBP >90 mmHg (standing) & restore plasma volume.

• Surgical Resection: Definitive treatment, aiming for complete tumor removal.
  • Approach: Laparoscopic adrenalectomy is gold standard. Open surgery for large (>6-8 cm), invasive, or multiple tumors.
• Intra-operative Care:
  • Vigilant arterial BP monitoring is crucial.
  • Manage hypertensive crises (e.g., IV nitroprusside, phentolamine).
  • Treat hypotension post-adrenal vein ligation (aggressive fluids, vasopressors).

⭐ The "no-touch" isolation technique for the adrenal vein is crucial during surgery to minimize tumor manipulation and prevent massive catecholamine release.

Family Ties & Oddballs - Beyond Typical

High‑Yield Points - ⚡ Biggest Takeaways

• Classic Triad: Episodic headache, sweating, tachycardia.
• Diagnosis: ↑ plasma free metanephrines or ↑ 24-hr urinary fractionated metanephrines & catecholamines.
• Pre-op: α-blockade (e.g., phenoxybenzamine) first, then β-blockade if needed (prevents crisis).
• Rule of 10s: 10% bilateral, extra-adrenal, malignant, pediatric, familial (some now higher).
• Most common extra-adrenal tumor site: Organ of Zuckerkandl.
• Key Associations: MEN 2A/2B, VHL, NF1.
• Treatment: Surgical resection after medical stabilization_._