Adrenal incidentalomas showing unilateral. concordant visualization by adrenocortical scintigraphy: Comparison with adenomas in Cushing's syndrome

An adrenocortical adenoma causing Gushing's syndrome (Gushing's adenoma) pr oduces a unilateral concordant visualization (UCV) imaging pattern in which the adenoma is only visualized on radioiodocholesterol adrenocortical scin tigraphy. But because this imaging pattern is also noted in some patients w ith adrenal incidentalomas, we examined whether the UGV-incidentaloma was e ssentially identical with Gushing's adenoma and would develop Gushing's syn drome. The subjects were 9 patients with UCV-incidentalomas (mean size, 30 mm; range, 20-45 mm) and 6 patients with Gushing's adenomas (mean size, 28 mm; range, 25-35 mm). Endocrinological evaluations showed several abnormali ties including blunted diurnal rhythm of plasma cortisol within the normal range, low plasma ACTH and/or high 24-hr urinary 17-OHCS levels in 8 of 9 p atients with UCV-incidentalomas, but these abnormalities did not meet the d iagnostic criteria of Cushing's syndrome. Adrenal uptake of the tracer in t he patients with UCV-incidentalomas was not statistically different from th at in the patients with Gushing's adenomas and had no relationship with hor monal values in either patient group. Tumor size on CT correlated with the levels of 24-hr urinary 17-OHCS (r = 0.75, p = 0.02) and plasma cortisol at 7 : 00 (r = 0.82, p = 0.007) in the patients with UCV-incidentalomas, but not in the patients with Gushing's adenomas. Although 3 UCV-incidentalomas increased slightly in size, none of 9 patients with UCV-incidentalomas has developed Cushing's syndrome for 4 to 52 months. These results suggest that the UGV-incidentaloma may be essentially different from the Gushing's aden oma and unlikely to develop Gushing's syndrome.