Reliability of adrenal computed tomography in predicting the functionality of adrenal incidentaloma

Adrenal incidentaloma (AI) is an adrenal mass discovered accidentally during abdominal or chest imaging techniques not aimed to adrenal gland assessment. Guidelines suggested confirming the benignity of AI radiologically and excluding hormonal dysfunctions. This study evaluated the reliability of computed tomography (CT) scan radiological parameters in predicting the functionality of AI.

A cross-sectional study performed in Faiha Specialized Diabetes, Endocrine and Metabolism Centre from July 2017 to July 2018, involving 38 patients (23 females [60.5%]) harbouring 43 AI referred for evaluation. For all patients, we assessed history, physical examination, radiological parameters of AI by CT scan (native Hounsfield unit [HU]), maximum diameter and absolute percentage washout [APW] and blood investigations (glycated haemoglobin, adrenocorticotropic hormone, aldosterone, renin, aldosterone/renin ratio, normetanephrine, metanephrine, dehydroepiandrosterone sulphate, cortisol and 1 mg overnight dexamethasone suppression test).

Native CT adrenal HU ≥18.5 was statistically significant seen in most functional AI (FAI) (P = 0.006), especially in patients with mild autonomous cortisol excess (MACE) and pheochromocytoma (PCC) with P = 0.02 in both. Maximum diameter was significantly high (≥40 mm) in PCC and congenital adrenal hyperplasia (CAH) (P = 0.018 and 0.008, respectively). APW was significantly < 60% only in PCC (P = 0.02).

Native HU was the most significant radiological parameter in predicting the functionality of FAI, MACE and PCC, but not in CAH and aldosterone-producing adenoma. The maximum diameter was significant in predicting the PCC and CAH, whereas the APW was significant in predicting PCC only.