Diagnosis of Small Adrenal Pheochromocytomas by Adrenal Venous Sampling with Glucagon Stimulation Test

Background: Pheochromocytoma develops in 0.1–0.5% of the hypertensive population between the ages of 30–50 years and is classically characterized by either sustained or paroxysmal hypertension, flushing, sweating, palpitations, and severe anxiety.Objectives: To demonstrate the safety and usefulness of bilateral adrenal venous sampling (BAVS) in patients with pheochromocytoma, but with negative imaging resultsPatients and Methods: We used BAVS with glucagon stimulation (1 mg, IV bolus) and measured stimulated fractionated catecholamines (norepinephrine [NE] and epinephrine [EPI]).Results: We performed BAVS with glucagon stimulation on 41 patients who presented with signs and symptoms highly suggestive of the presence of pheochromocytoma, and also had equivocal imaging results. Twenty patients were diagnosed with unilateral pheochromocytoma. The minimum predictive cut-off value for the EPI ratio of affected vs. unaffected sides in diagnosing a unilateral pheochromocytoma was 6.8 (sensitivity; 88.9%, specificity, 87.5%, P = 0.001). The minimum predictive cut-off value for the norepinephrine (NE) ratio of affected vs. unaffected sides was 3.8 (sensitivity; 90%, specificity; 81.2%, P = 0.001). The 2-min post glucagon-stimulated levels of affected versus unaffected adrenals were: EPI; 29,162 ± 8,756 vs. 1,136 ± 546 pg/ml (ratio = 25.7) and NE; 7,156 ± 1,399 vs. 760 ± 228 pg/ml (ratio = 9.4). The EPI:NE ratio on the affected side was significantly higher (4.1 vs. 1.5, P 0.001). During the follow-up period, patients who did not require post-operative medication were those who had a shorter duration of hypertension (4.8 ± 3 vs. 10 ± 10.8 years).Conclusions: BAVS with glucagon stimulation is a safe and useful approach for early diagnosis of pheochromocytoma.