What is pheochromocytoma?
- Pheochromocytoma, derived from the neural crest, is one ofthe surgically curable hypertensive syndromes.
- There is no gender predilection
Short note on Pheochromocytomas [TU 2062/5]
Rule of 10 in pheochromocytoma?
- 10% are extra-adrenal (head, neck, thorax, abdomen, and pelvis)
- 10% of sporadic pheochromocytomas are bilateral (in familial cases, bilaterality is seen in 50% of cases)
- 10% are malignant
- 10% are not associated with hypertension
- 10% of cases occur in children.
However, this rule has been challenged repeatedly. Up to 25% of pheochromocytomascan be extra-adrenal. Similarly, familial cases account for up to 30% of tumors at presentation
Clinical features of Pheochromocytoma?
Clinical features and management of pheochromocytoma. [TU 2062]
The triad of headache, episodic sudden sweating,and palpitation is a classic hallmark of pheochromocytoma.
- Hypertension - paroxysmal, usually triggered by emotional upsets
- Headache is a frequent complaint
- Increased sweating
- Tachycardia with palpitations
- Postural hypotension is a frequent finding, as a result of diminished plasma volume.
- Weight loss
- Decreased gastrointestinal motility, anxiety, and psychic instability are also common and due to excess circulating catechols.
What are metanephrins and VMA?
- Metanephrine is a metabolite of epinephrine created by action of catechol-O-methyl transferase on epinephrine.
- Vanillylmandelic acid (VMA) is an end-stage metabolite of the catecholamines, epinephrine, and norepinephrine. It is produced via intermediary metabolites.
Chromogranin A Testing?
Chromogranin A belongs to a group of compounds known as granins, which exist in the secretory vesicles of the neuroendocrine and the nervous systems. Elevation of serum chromogranin A levels has been documented in patients with pheochromocytoma.
Initial workup for suspected pheochromocytoma?
Biochemical diagnosis of Pheochromocytoma?
Measurements of metanephrines (MNs) or catecholamine are more useful than measurement of vanillylmandelic acid.
- Norepinephrine: 10–100 μg/24 h
- Epinephrine: Up to 20 μg/24 h
- Normetanephrine and metanephrine: <1.5 mg/24 h
- Vanillylmandelic acid (VMA): 2–9 mg/24 h
- Norepinephrine: 100–200 pg/mL
- Epinephrine: 30–50 pg/mL
Measurements of metanephrines (MNs) or catecholamine aremore useful than measurement of vanillylmandelic acid
Investigations for pheochromocytoma (tumor localization)?
- CT scan - Initial imaging of choice.
- MRI - may be superior than CT scan in extra-adrenal tumor
- MIBG scanning
What is MIBG scanning?
The compoundis taken up by pheochromocytomas, ganglioneuromas,neuroblastomas, and other neural crest tumors, as well as some carcinoids.
MIBG scans have great utility in the localization of
- (1) small lesions,
- (2) extraadrenal lesions,
- (3) bilateral lesions, and
- (4) metastatic deposits in patients with malignant tumors.
Diagnostic strategy of pheochromocytoma?
- Patients in whom there is a high index of clinical suspicion and those who have a greater than twofold elevation of urine catechols should undergo an adrenal CT.
- If the CT reveals a unilateral tumor and the contralateral adrenal is normal, the diagnosis is established.
- Patients with familial syndromes and those in whom cancer is suspected should undergo MIBG scanning to determine the extent of disease.
- If the adrenal CT is negative, MIBG scanning or MRI of the chest and abdomen is indicated to localize the tumor.
If the clinical suspicion is low and urine catechols are normal, imaging procedures are not indicated.
Preoperative preparation of Pheochromocytoma?
Discuss the pre and post-operative management of pheochromocytoma. [TU 2066/1, 64/12, 59]
Outline the pre, per and post-operative management of pheochromocytoma. [TU 2057,59]
Describe the pre, per and post operative management of pheochromocytoma. [TU 2057]
- A) 7-14 days preoperatively as Outpatient -
- 1. Alpha-Blockade: Phenoxybenzamine 10 mg PO bid, target BP <160/90
- • Increase by 10-20 mg increments every 2-3 days.
- • Total dose of 1 mg/kg usually sufficient
- 2. If patient develops tachycardia and/or cardiac arrythmia : Beta-Blockade (do not start before adequate alpha-blockage):
- Atenolol 12.5-25 mg PO bid or tid or
- Metoprolol 25-50 mg PO tid or qid.
- Some institutions use Metyrosine 250mg QID. (catechoamine synthesis bloakage)
- 3. If BP still poorly controlled : Calcium channel blockade:
- Amlodipine 10-20 mg daily or
- Nicardipine 60-90 mg daily or
- Nifedipine 30-90 mg daily or
- Verapamil 180-540 mg
- B) 1-2 days preoperative as inpatient
- 1. Monitor BP and HR:
- • BP goal: 120-130/80 mm Hg in seated position
- • Last dose of phenoxybenzamine on night before surgery (no morning dose, to avoid postop hypotension)
- • Mid postural hypotension (SBP >90 mm Hg) is acceptable and a sign of appropriate blockade
- 2. Intravascular volume restoration:
- • IV fluids
- • 1-2 L bolus night before surgery
Treatment of Pheochromocytoma?
Surgical excision - total adrenalectomy or Partial adrenalectomy (For small tumors or patients at risk forbilateral disease)
Metastatic cases - Radioactive 131I-MIBG
Intraoperative complication during excision of pheochromocytoma?
1. Acute hypertensive crises - Endotracheal intubation and manipulation of the adrenal gland can both induce release of catecholamines and, potentially, a hypertensive crisis.
Higher preoperative plasma norepinephrine concentration, larger tumor size (>4 cm), and more pronounced postural blood pressure fall after alpha-blockade (>10 mmHg) correlated with intraoperative hypertensive events.
Management — Treatment options for hypertensive crises include intravenous sodium nitroprusside, phentolamine, or nicardipine.
●Sodium nitroprusside is an ideal vasodilator for intraoperative management of hypertensive episodes because of its rapid onset of action and short duration of effect. It is administered as an intravenous infusion at 0.5 to 5.0 mcg/kg/min and adjusted every few minutes for target blood pressure response
2. Cardiac arrhythmias should be managed with lidocaine or esmolol
Post-operative complication of excision of pheochromocytoma?
- Postoperative hypotension can be avoided by adequate fluid replacement
- Hypoglycemia (due to removal of catecholamine suppression of insulin secretion) can be managed with glucose infusion.
- The only reliable clue to the presence of a malignant pheochromocytoma is local invasion or distant metastases.
- Pathologic appearance is unreliable.
- Long-term follow-up is paramount, because recurrences are reported even 15 years after the initial resection of a localized lesion.