Pheochromocytoma

-Tumor arising from chromaffin cells and sustentacular cells of the adrenal medulla or extraadrenal paraganglia.
- Classically secrete epinephrine, norepinephrine or dopamine.  However, can also secrete a host of other hormones.
- Distinction between benign and malignant is the presence of local invasion or presence of distant mets.

Presentation:
- Classic triad: (PHEo) Paroxysmal HTN, Palpatations, Headache, Excess sweating
- Most (90%) will present with some clinical manifestation, whereas 10% will present initially as an adrenal incidentaloma.
- Number of familial conditions associated with pheo - notably MEN2a and 2b.

Diagnosis:
- Most specific test is combination of 24 hr urine metanephrines and catacholamines.
- Plasma testing, while very sensitive, is very expensive and not as specific.
- Any elevated 24hr urine metanephrine or 2x normal 24 hr urine catacholamine result is considered positive.
- Many drugs (notably, TCAs) can falsely elevate urine catacholamines.
- CT abdo/pelvis most cost-effective method to localize pheo once diagnosed.  However, other modlities such as MRI, MIBG scan, and PET scan  may be used as adjunctive imaging tests.
- With newer contrast agents - precipitation of hypertensive crisis is not as much of a concern and non-contrast CT not necessary

Perioperative Management:
- Important step in operative management in order to prevent hypertensive crisis intra-op.
- Unopposed alpha-stimulation once pheo removed will cause vasoconstriction and decreased intravascular volume
- alpha-blockade should begin immediately once diagnosis is made
- Phenoxybenzamine started at 20-30 mg qD in divided doses.  Increase dose until the pt is symptomatic with orthostatic hypotension and/or nasal stuffiness.
- in order to combat side-effects instruct pt to increase salt and fluid intake.
- Beta-blockade with propranolol can be added to manage tachycardia, arrythmias or ischemia