Pheochromocytoma: An Incidental Finding in an Asymptomatic Older Adult With Renal Oncocytoma

Subsequent workup after adrenalectomy, including urinary and fractionated plasma metanephrines and catecholamines, were not consistent with catecholamine hypersecretion. A 24-hour urine fractionated metanephrines test has about 98% sensitivity and 98% specificity. Elevated plasma norepinephrine was thought to be due to renal failure because it was < 3-fold the upper limit of normal, which is considered to be a possible indication of pheochromocytoma.^17,18 The nuclear medicine (iobenguane I-123) tumor, SPECT, and FDG-PET CT studies were negative for residual pheochromocytoma. Other imaging studies to consider in patients with suspected catecholamine-secreting tumor with positive biochemical test and negative abdominal imaging are a whole-body MRI scan, 68-Ga DOTATATE (gallium 68 1,4,7,10-tetraazacyclododecane-1,4,7,10 tetraacetic acid-octreotate) or FDG-PET scan.¹⁹

In a review of 54 autopsy-proven pheochromocytoma cases by Sutton and colleagues in 1981, 74% of the patients were not clinically suspected for pheochromocytoma in their life.⁴ Similarly, in a retrospective study of hospital autopsies by McNeil and colleagues, one incidental pheochromocytoma was detected in every 2031 autopsies (0.05%).²⁰ In another case series of 41 patients with pheochromocytoma-related adrenalectomy, almost 50% of the pheochromocytomas were detected incidentally on imaging studies.²¹ Although the number of incidental findings are decreasing due to advances in screening techniques, a significant number of patients remain undiagnosed. Multiple cases of diagnosis of pheochromocytoma on autopsy of patients who died of hemodynamic instability (ie, hypertensive crisis, hypotension crisis precipitated by surgery for adrenal or nonadrenal conditions) are reported.³ To the best of our knowledge, there are no case reports published on the diagnosis of pheochromocytoma after adrenalectomy in an asymptomatic patient without intraoperative complications.

The goal of preoperative medical therapy includes BP control, prevention of tachycardia, and volume expansion. The preoperative medications regimens are combined α- and β-adrenergic blockade, calcium channel blockers, and metyrosine. According to clinical practice guidelines of the Endocrine Society in 2014, the α-adrenergic blockers should be started first at least 7 days before surgery to control BP and to cause vasodilation. Early use of α-blockers is required to prevent cardiotoxicity. The β-adrenergic blockers should be started after the adequate α-adrenergic blockade, typically 2 to 3 days before surgery, as early use can cause vasoconstriction in patients with pheochromocytoma. The α-adrenergic blockers include phenoxybenzamine (nonselective long-acting nonspecific α-adrenergic blocking agent), and selective α-1 adrenergic blockers (doxazosin, prazosin, terazosin). The β-adrenergic blocker (ie, propranolol, metoprolol) should be started cautiously with a low dose and slowly titrated to control heart rate. A high sodium diet and increased fluid intake also are recommended 7 to 14 days before surgery. A sudden drop in catecholamines can cause hypotension during an operation. Continuous fluid infusions are given to prevent hypotension.²² Similarly, anesthetic agents also should be modified to prevent cardiotoxic effects. Rocuronium and vecuronium are less cardiotoxic compared with other sympathomimetic muscle relaxants. Short-acting anesthetic agents, such as fentanyl, are preferred. α-blockers are continued throughout the operation. Biochemical testing with fractionated metanephrines is performed about 1 to 2 weeks postoperatively to look for recurrence of the disease.²³

Secondary causes of hypertension are suspected in multidrug resistant or sudden early onset of hypertension before aged 40 years. Pheochromocytoma is a rare cause of secondary hypertension, and older adult patients are rarely diagnosed with pheochromocytoma.²⁴ In this report, pheochromocytoma was detected in a 72-year-old hypertensive patient. Therefore, a pheochromocytoma diagnosis should not be ignored in the older adult patient with adrenal mass and hypertension treated with more than one drug. The authors recommend any patient undergoing surgery with adrenal lesion should be considered for the screening of possible pheochromocytoma and prepared preoperatively, especially any patient with renal cell carcinoma with adrenal metastasis.

Conclusions

Asymptomatic pheochromocytoma is an unusual but serious condition, especially for patients undergoing a surgical procedure. An adrenal mass may be ignored in asymptomatic or mildly symptomatic older adult patients and is mostly considered as adrenal metastasis when present with other malignancies. Fortunately, the nephrectomy and adrenalectomy in our case of asymptomatic pheochromocytoma was uneventful, but pheochromocytoma should be ruled out before a surgical procedure, as an absence of medical pretreatment can lead to serious consequences. Therefore, we suggest a more careful screening of pheochromocytoma in patients with an adrenal mass (primary or metastatic) and hypertension treated with multiple antihypertensive drugs, even in older adult patients.