Potential pitfalls in the diagnosis of phaeochromocytoma.

Six patients being evaluated for phaeochromocytoma had misleading investigative findings: all initially had raised urinary catecholamine levels, and five had adrenal masses on imaging studies. Adrenalectomy in these five patients revealed only one pathologically confirmed phaeochromocytoma. Tricyclic antidepressant use produced misleading elevations in urinary catecholamine levels in three patients. 24-hour urine studies should be performed at least twice, after eliminating confounding factors (stressors, medications).