A pheochromocytoma is a very rare endocrine tumor that usually arises from the adrenal medulla. Although it is a rare entity, it is commonly tested on exams and boards due to it’s classic presentation.
It is a cause of secondary hypertension and remains an important exclusion in the patient with documented hypertension in whom a work up for secondary hypertension is initiated. Additionally, if undiagnosed, there can be severe, even lethal complications.
The majority of pheochromocytomas are found in extra-adrenal chromaffin tissue. The tumor secretes catecholamines into the systemic circulation. When a catecholamine binds to an adrenergic receptor, norepinephrine and epinephrine are released.
The resultant stimulation and activation of alpha and beta receptors causes constriction of smooth muscle which results in elevated blood pressure. When beta receptors are activated, the result is tachycardia. (Campara and Porter, 2016).
Incidence of Pheochromocytoma
As discussed previously, the condition is extremely rare. The incidence of patients with documented hypertension who have a pheochromocytoma is about 0.2%. There are only 500 to 1,000 cases documented in the United States each year. The distribution between males and females is equal and usually is diagnosed in the 4th or 5th decade of life.
Most patients with a documented pheochromocytoma have an idiopathic diagnosis. There are a subset of patients who do have familial causes. Some of the familial aspects related to pheochromocytoma include familial pheochromocytoma, familial paraganglioma, and Multiple endocrine neoplasia type 2A, and 2B. These are autosomal dominant inheritances.
Other rarer familial inheritances do exist as well. Patients with concern for family history of adrenal tumor or other should be thoroughly investigated to identify what disease is present.
As with many other medical conditions, the presentation of pheochromocytoma is on a spectrum. Patients may present with classic symptoms, or may present in acute hypertensive emergency.
The somewhat classic triad of symptoms include headache, palpitations, and diaphoresis. Other classic symptoms include tremor, weight loss due to increased metabolic drive, anxiety, facial flushing as well as shortness of breath.
A pneumonic to help with the diagnosis includes the “5 Ps”. This includes the nature which is paroxysmal, perspiration, palpitations, pain including headache, and pressure in reference to the florid elevation in blood pressure.
Unfortunately, there is a high risk of sudden death in patients in whom a pheochromocytoma has not been documented or diagnosed during the perioperative setting as elevations in blood pressure can be catastrophic and life-threatening.
Based on the symptoms, the differential diagnosis is broad.
Patients with only small elevations in blood pressure may be incorrectly diagnosed with essential primary hypertension. Other considerations in the differential diagnosis include hyperthyroidism, withdrawal from medication, drug use including stimulants, anxiety attack and incorrectly measured blood pressure.
The diagnosis of pheochromocytoma can be accomplished via measurements of urine catecholamines. A 24 hour metanephrine and catecholamine collection is 90% sensitive for the diagnosis. It is thought that the greater the level of catecholamines in urine, the larger the tumor.
Additionally, urine vanillymandelic acid, a metabolite of norepinephrine can be used and has similar sensitivity and specificity.
Another methodology for diagnosis is a CT/MRI of the abdomen, which can assess presence or absence of a tumor, size of tumor, and identify location.
It is important to note that in patients with suspicion of pheochromocytoma, intravenous contrast can actually cause a hypertensive crisis, so caution must be taken.
Once the disease has been diagnosed, careful blood pressure control must be initiated. The treatment for pheochromocytoma is surgical. It is very important to note that giving a patient a beta blocker with pheochromocytoma can be FATAL.
Returning to the pathophysiology, one will note that if given a beta blocker, there will be unopposed alpha agonist activity which can precipitate a fatal hypertensive crisis.
Initial blood pressure control is achieved with phenoxybenzamine. Interestingly, patients on this medication have a high rate of orthostasis and it is suggested that they increase salt intake to upwards of 5,000 mg/day. Once blood pressure has improved, a beta blocker such as propranolol can be used. As discussed above, the definitive treatment is surgical.
Surgical intervention should be performed by an experienced surgical team, as morbidity and mortality can be high. Unfortunately, there can be up to a 15% recurrence rate post-surgery. Careful titration and monitoring of intraoperative blood pressure is paramount and may require use of nitroprusside, nicardipine, or other parenteral anti-hypertensive agents.
Summary of Pheochromocytoma
Although clinically rare, a pheochromocytoma has important clinical and educational pearls.
The classic presentation may include a patient in their mid-forties with paroxysmal episodes of headache, diaphoresis, palpitations, and severely elevated hypertension.
The urine metanephrines or 24 hour urine vanillymandelic acid is sensitive and specific for pheochromocytoma. Patients with suspected pheochromocytoma should avoid CT scan contrast, as this can produce a hypertensive emergency.
Once blood pressure control is obtained first by alpha blockade and then beta blockade, the treatment of this condition is surgical.
Campara, M.C. and Porter, A.C. (2016). Pheochromocytoma. The Five Minute Clinical Consult.
Papadakis, Maxine (2013). Pheochromocytoma and Paraganglioma. Current Medical Diagnosis and Treatment. McGraw Hill.
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