Three biochemical tests for the diagnosis of pheochromocytoma were evaluated in 24 patients with proved tumors and 40 patients whose clinical picture was suspect but who had no evidence of the disease. Measurement of resting, supine plasma catecholamines (by radioenzymatic assay) was more useful than either 24-hour urinary vanillylmandelic acid (VMA) or metanephrines or both. In only one of 23 patients with pheochromocytoma were plasma catecholamines within the range of those in patients without pheochromocytoma, as compared with urinary VMA in 11 of 22, urinary metanephrines in five of 22 and both metabolites in three of 22. These studies reaffirm the value of plasma catecholamines in the diagnosis of pheochromocytoma and indicate that urinary catecholamine metabolites are less useful. The poor correlation between the height of arterial pressure and circulating levels of catecholamines suggests that the regulation of arterial pressure in pheochromocytoma is complex.
Pheochromocytoma, a relatively rare (<0.05% of hypertensives), catecholamine-secreting tumor, is almost always lethal unless recognized and appropriately treated. Clinical and biochemical manifestations are mainly caused by excess circulating catecholamines and hypertension. Manifestations mimic many conditions, which may result in erroneous diagnoses and improper treatment. Sustained or paroxysmal hypertension associated with headaches, sweating, or palpitations, occurs in 95% of patients, but at least 5% are normotensive. All patients with manifestations of hypercatecholaminemia or coexisting neoplasms should be investigated for pheochromocytoma. Plasma free metanephrines and fractionated urinary metanephrines are the most sensitive (about 100%) chemical tests for diagnosing sporadic and familial pheochromocytomas; plasma and urinary catecholamines and total metanephrines are fairly sensitive for identifying sporadic cases but are less sensitive for familial tumors. The clonidine suppression test helps exclude other conditions that may elevate plasma and urinary catecholamines and their metabolites. Magnetic resonance imaging is more sensitive than computed tomography for localizing pheochromocytomas; iodine-131-metaiodobenzylguanidine (131I-MIBG) tumor uptake confers specificity. Surgical resection is successful in 90% of cases, but 10% of tumors are malignant. Pheochromocytomas <5 cm in diameter can be removed laparoscopically; larger tumors should be removed by open surgery. Drug treatment prior to and during surgery is mandatory; drug treatment, chemotherapy, and radiation therapy are used to treat malignant lesions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.