Clinical Images
Pheochromocytoma
The catecholamine bomb in the adrenal medulla. Block the alpha first, or the patient codes on the table.
The Classic Pattern
The Rule of 10s
Tap each card. Front = the rule. Back = why the board cares.
Why the symptoms hit the way they do
- Headache: the catecholamine spike yanks BP up β cerebral vessels stretch β pounding pain.
- Sweating: sympathetic outflow hits sweat glands directly. No fever, just soaked.
- Palpitations: beta-1 receptors on the heart get hammered β rate and force both jump.
- Hypertension: alpha-1 on vessels clamps everything down. Either paroxysmal spikes or sustained baseline-high.
- Pallor + cold extremities: alpha-1 vasoconstriction. Pheo patients blanch they don't flush. That's how you separate it from carcinoid.
Workup
Diagnose, Then Image
Biochemistry first. Imaging only after the labs say so.
Plasma free metanephrines
Best screening test, highest sensitivity. Catch the easy positives.
Why: metanephrines are the breakdown product. Tumors leak constantly even between BP spikes, so the metabolite stays elevated.
24-hour urine metanephrines + catecholamines
Best confirmatory test, highest specificity. This is the answer when the clinical medicine ask "most specific."
Why: 24 hours captures the whole day, including a paroxysm. Spot catecholamines miss the spell.
CT or MRI of the adrenals
Localize the tumor after labs are positive. Never image first.
Why: imaging an asymptomatic adrenal nodule with no biochem support β you find the 4% incidentaloma, not the pheo.
MIBG scan
For extra-adrenal, multifocal, or metastatic disease. MIBG (a norepi analog) lights up chromaffin tissue anywhere.
Why: a CT can't scan the whole body for paraganglioma. MIBG can.
The Treatment Trap
Order Matters. Get It Wrong, You Kill Them.
Click the steps in the correct order. Beta-block first and the patient codes.
Why Ξ± before Ξ²? The mechanism that actually sticks.
Catecholamines hit two main vascular receptors:
- Ξ±-1 on blood vessels β squeezes them shut (vasoconstriction, HTN).
- Ξ²-2 on blood vessels β relaxes them (vasodilation, mild offset).
The pheo's catecholamines are pushing on both at once. The Ξ²-2 dilation is a tiny pressure-release valve.
If you give a non-selective Ξ²-blocker first you slam the Ξ²-2 release valve shut while Ξ±-1 is still wide open and hammering. Result: unopposed alpha vasoconstriction β severe hypertensive crisis β stroke or MI on the table.
So: Ξ±-block first with phenoxybenzamineNon-selective, irreversible Ξ±-blocker. "Irreversible" matters: even when the tumor dumps a fresh load of catecholamines mid-surgery, the receptors are already permanently blocked. The protection doesn't wear off. for 10-14 days. Then add a Ξ²-blocker for the reflex tachycardia. Then operate.πAlphabet rule: A before B. Never B before A.
See It Happen
The Receptor Pressure Stage
Watch the vessel. Pick a blockade strategy and see what the lumen does in real time.
Reason It Out
Workup Decision Tree
Commit to an answer first. Each step reveals the consequence only after you choose.
The Genetic Crowd
MEN 2A vs 2B vs VHL
Pheo doesn't travel alone. Know the company it keeps.
MEN 2A
RET mutation- Pheochromocytoma
- Medullary thyroid cancer (calcitonin)
- Parathyroid hyperplasia (chief cells)
3 Ps of MEN 2A: Pheo, Parathyroid, Papillary⦠wait, no. Medullary thyroid. Adjust.
MEN 2B
RET mutation- Pheochromocytoma
- Medullary thyroid cancer
- Marfanoid body habitus
- Mucosal neuromas (lips, tongue, GI)
- NO parathyroid involvement
Tall, lanky kid with bumpy lips and a tongue full of nodules β MEN 2B until proven otherwise.
von Hippel-Lindau
VHL tumor suppressor- Pheochromocytoma
- CNS & retinal hemangioblastomas
- Clear-cell RCC
- Pancreatic & renal cysts
VHL = pheo + tumors that bleed. Hemangioblastomas, retinal angiomas, RCC. Vascular weirdness everywhere.
The Patient
Episodic HTN, Sweating, Headache
A 34-year-old woman walks in. Pick the diagnosis from the story.
What is pheochromocytoma actually doing?
It's a tumor of the chromaffin cellsChromaffin cells live in the adrenal medulla. They're basically modified sympathetic neurons, they pump out epi/norepi when the sympathetic nervous system fires. in the adrenal medulla. Those cells normally release epinephrine and norepinephrine when your sympathetic nervous system fires. The tumor releases them on its own in unpredictable bursts.
That's why the symptoms are paroxysmal the tumor dumps catecholamines, the patient spikes, the catecholamines wash out, the patient feels normal. Repeat.
Some pheos also pump out dopamine. Extra-adrenal versions (paragangliomas) often secrete only norepi.
The Syndromic Zoo
The Lineup
Seven villains. Pheo is just the start. Tap each card to flip.
Pheochromocytoma
- Origin: adrenal medulla chromaffin cells
- Rule of 10s: 10% bilateral, 10% extra-adrenal, 10% malignant, 10% in kids
- 5Hs: Headache, Hypertension, Hyperhidrosis, Hyperglycemia, Hyper-thyroid mimic
- Screen: plasma free metanephrines (best sensitivity)
- Board pearl: alpha-block first, NEVER beta-block first
Paraganglioma
- Location: extra-adrenal chromaffin tissue
- Sympathetic (abdominal): secretes catecholamines, like pheo
- Parasympathetic (head/neck): no catecholamines, but mass effect
- Classic clue: HTN spike when voiding = bladder wall paraganglioma
- Board pearl: MIBG scan finds extra-adrenal tumors CT misses
MEN 2A
- Components: Pheo + Medullary Thyroid Cancer + Parathyroid hyperplasia
- Gene: RET proto-oncogene mutation
- Board pearl: always screen for pheo BEFORE thyroid surgery (intraop catecholamine dump = fatal)
- Memory: 2A = Adenomas (parathyroid)
MEN 2B
- Components: Pheo + Medullary Thyroid Cancer + mucosal neuromas + Marfanoid habitus
- Gene: RET mutation (different hotspot than 2A)
- MTC: more aggressive than in 2A, presents younger
- Memory: 2B = Bumps (neuromas) + Body (Marfanoid)
Von Hippel-Lindau
- Components: Pheo + hemangioblastomas (cerebellum/retina) + clear cell RCC + pancreatic cysts
- Gene: VHL tumor suppressor gene
- Vibe: tumors that bleed (hemangio = blood vessel)
- Board pearl: retinal angioma causing vision loss in a young person = VHL workup
Neurofibromatosis Type 1
- Gene: NF1 tumor suppressor, chromosome 17
- Classic findings: cafe-au-lait spots, neurofibromas, Lisch nodules (iris)
- Pheo: less common than VHL/MEN 2 but still a board item
- Optic glioma: can cause vision loss in childhood
- Board pearl: "cafe-au-lait + axillary freckling + neurofibromas" = NF1
Succinate Dehydrogenase Mutations
- Subtypes: SDHB, SDHC, SDHD
- SDHB: highest malignant risk of all hereditary pheo syndromes
- Syndrome: hereditary paraganglioma-pheochromocytoma syndrome
- Board pearl: young patient with malignant pheo/paraganglioma = check SDH genes
Clinical Reasoning
Decision Tree: Pheo Workup
Follow the clinical steps. Tap each branch to reveal the next move.
Order: plasma free metanephrines (best sensitivity, can be drawn any time) OR 24-hour urine metanephrines (high specificity, good confirmation).
Do NOT image first. Imaging without biochem confirmation finds incidentalomas and confuses the workup.
Pheo can present with sustained (not just episodic) HTN, especially in familial cases. If index of suspicion exists (family history, young patient, resistant HTN), order plasma metanephrines before dismissing it.
CT or MRI of the adrenals. CT preferred for adrenal (sensitivity ~90%). MRI preferred if: pregnancy, allergy to contrast, or suspected extra-adrenal tumor.
If CT is negative but biochem is strongly positive: whole-body MIBG scan or PET to find extra-adrenal paraganglioma.
If suspicion remains high (paroxysmal spells, family history), repeat testing during a symptomatic episode. Catecholamines have a short half-life; a random draw between spells can be falsely negative. Metanephrines are more stable but can occasionally miss low-secretors.
Phenoxybenzamine (non-selective irreversible alpha-blocker) for 10-14 days minimum.
Goals: normalize BP, relieve vasoconstriction, allow plasma volume to expand.
Expect reflex tachycardia once vessels dilate. Then add beta-blocker (propranolol) AFTER alpha is established. Never beta-block first = unopposed alpha = hypertensive crisis on the table.
Surgical manipulation of a pheo releases massive catecholamines. Without pre-op alpha-blockade, intraoperative HTN crisis, arrhythmia, and death are likely.
The pre-op alpha-blockade period is non-negotiable. Minimum 10-14 days. Some centers use 4-6 weeks.
Once alpha is covered and BP is stable: add propranolol to control reflex tachycardia.
Then: laparoscopic adrenalectomy (preferred for tumors <6cm).
Post-op: watch for hypoglycemia (catecholamine withdrawal drops counter-regulatory hormones) and hypotension (vasodilation now unopposed by tumor).
Prove It
Board Walkthrough
25-vignette bank, 5 dealt per round, answer choices shuffled, never-repeat within a round. Tap a wrong answer first to see why it almost works, then read the glowing clues.