Pheochromocytoma

What is Pheochromocytoma?

Pheochromocytoma (also known as chromaffin tumor) is a rare disease, characterized by paroxysmal or sustained hypertension due to oversecretion of the catecholamines epinephrine and norepinephrine. By some estimates, about 0.5% of newly diagnosed patients with hypertension have pheochromocytoma; this tumor is usually benign but is malignant in a few patients.

Pheochromocytoma affects all races and both sexes and is typically familial. Although this disorder is potentially fatal, the prognosis is generally good with treatment.

Causes of Pheochromocytoma

Pheochromocytoma stems from a chromaffin cell tumor of the adrenal medulla or sympathetic ganglia, more commonly in the right adrenal gland than in the left. Extra-adrenal pheochromocytomas may be located in the abdomen, thorax, urinary bladder, and neck and in association with the 9th and 10th cranial nerves.

Pheochromocytoma may be inherited as an autosomal dominant trait.

Signs & Symptoms of Pheochromocytoma

The following symptoms are listed from the most common to the least common:

• Nervous shaking (tremors)
• Anxiety / nervousness
• Excess sweating
• Weight loss
• Pain in the lower chest or upper abdomen
• Headaches
• Rapid heart rate
• Irregular heartbeat (palpitations)
• Feeling of extreme fright
• Pale skin

Diagnostic tests

Diagnosis of pheochromocytoma is usually based on the following test findings:

• Increased urinary excretion of total free catecholamine and its metabolites, vanillylmandelic acid (VMA) and metanephrine, as measured by analysis of a 24-hour urine specimen, confirms pheochromocytoma.
• Labile blood pressure necessitates urine collection during a hypertensive episode and comparison of this specimen to a baseline specimen. Direct assay of total plasma catecholamines may show levels 10 to 50 times higher than normal.
• Computed tomography (CT) scanning or magnetic resonance imaging of the adrenal glands is usually successful in identifying the intra-adrenal lesions. CT scanning, chest X-rays, or abdominal aortography may be used to identify extra-adrenal pheochromocytomas.

Treatment

Surgical removal of the tumor is the treatment of choice. To decrease the patient's blood pressure, the alpha-adrenergic blocking agents phentolamine or phenoxybenzamine, or metyrosine (which blocks catecholamine synthesis), are administered from 1 day to 2 weeks before surgery or invasive diagnostic procedures. A beta-adrenergic blocking agent (propranolol or atenolol) may also be used after achieving alpha blockade. Prazosin, labetalol, and nifedipine may also be used.

Postoperatively, the patient may require I.V. fluids, plasma volume expanders and, possibly, transfusions if marked hypotension occurs. However, persistent hypertension in the immediate postoperative period is more common.

If surgery isn't feasible, alpha- and beta-adrenergic blocking agents - such as phenoxybenzamine and  propranolol, respectively - are beneficial in controlling catecholamine effects and preventing attacks. Research is being done to investigate the use of a combination of chemotherapeutic agents in treating inoperable malignant adrenal tumors.

Management of acute attacks or hypertensive crisis requires administration of phentolamine by I.V. push or drip or nitroprusside to normalize blood pressure.

Prevention Tips

Since little is known about the causes of pheochromocytoma, prevention methods are not available.