Correct!
1. Free plasma metanephrines or urinary metanephrines
Controversy persists regarding the best screening test for pheochromocytoma, Studies have demonstrated that plasma fractionated metanephrines have the highest sensitivity, and thereby the best NPV, and 24-hour urine for fractionated metanephrines has the best specificity and therefore the highest PPV. Our patient’s free plasma metanephrines were 402 pg/mL (normal <57) and free plasma normetanephrines 1327 pg/mL (normal <148). Since only about 1 in 300 patients evaluated for pheochromocytoma will turn out to have it, CT scanning would not be a cost effective screening tool. Urine 5-hydroxyindoleacetic acid (5-HIAA) is a diagnostic test for carcinoid tumor. Clinically carcinoid tumors present more commonly with "dry" flushing (flushing with no sweating) and nocturnal diarrhea.
The most important thing about pheochromocytoma is to clinically recognize when to suspect and test for it. . As many as 50-75% of pheochromocytomas demonstrable on autopsy were never clinically diagnosed. The classic triad of episodic headaches, diaphoresis and tachycardia is seen in only 25% of patients with pheochromocytoma (1). About 80-90% of patients have hypertension but 40-50% have only episodic hypertension. Orthostasis and acute cardiomyopathy such as seen in our patient are less common, but well described. Patient’s presenting with acute cardiomyopathy secondary to pheochromocytoma famously deteriorate if given beta-blockers, due to unopposed alpha sympathomimetic effect Another uncommon but classic presentation for a patient with undiagnosed pheochromocytoma is unexpected life-threatening hyper or hypotension during an unrelated surgical procedure.
Our patient underwent CT of the abdomen which showed a left adrenal mass consistent with pheochromocytoma (Figure 3).
Figure 3. Representative view of contrast enhanced abdominal CT scan.
About 10% of pheochromocytomas are multiple, about 10% are extra-adrenal and about 10% are malignant – but radiographical evaluation did not reveal evidence of any of these. The patient was treated with phenoxybenzamine (a non-competitive ganglionic alpha blocker) and then labetolol - only after alpha blockade was established. The patient was also put on a high sodium diet to help ameliorate volume contraction associated with untreated pheochromocytoma. It typically takes at least two weeks to prepare a pheochromocytoma patient for adrenalectomy .
The take home points of this presentation are:
Reference