Epinephrine fraction of adrenal vein blood in pheochromocytoma.

Variability in the levels of epinephrine (E) and norepinephrine (NE) in adrenal vein blood is thought to preclude their usefulness in caval sampling studies for localizing abdominal pheochromocytoma. In this study we demonstrate, in three patients, that the fraction of the total catecholamine level in the adrenal effluent represented by E (E fraction) may differentiate the normal adrenal medulla from the gland containing a pheochromocytoma. This observation is additionally supported by calculations of the E fractions, from adrenal venous E and NE reported recently, in three other patients with pheochromocytoma. Our data, combined with those from the literature, yield a mean E fraction, in adrenal vein blood, of 63.8 +/- 11.4 (SD)% for seven normal adrenal medullae, and of 28.5 +/- 4.8% for five glands bearing pheochromocytoma. The use of this parameter for lateralizing adrenal pheochromocytoma is suggested if other procedures are unable to demonstrate the tumor.