Role of CT-scanning, MRI, and radiocholesterol scintigraphy as noninvasive adrenal imaging in Cushing's syndrome. Clinico-pathological and radiological correlations in 67 patients undergoing adrenalectomy.

We report our experience using computed tomography (CT) scan, magnetic resonance imaging (MRI) and 75-Se-nor-cholesterol scintiscanning (NCS) in patients with Cushing’s syndrome who have undergone adrenalectomy. Between 1986-1997, 67 patients, 11 (16.4%) males (M) and 56 (83.6%) females (F), median age 44 years (range 19-69), with confirmed Cushing’s syndrome due to benign adrenal disease underwent unilateral or bilateral adrenalectomy and subsequent pathological examination of the removed adrenal glands. Patients were divided in two groups: Group A (unilateral adrenalectomy), 35 (52.2%) patients (F=31, M=4, median age 47 years), of which 33 (49.2%) had adrenocortical adenoma and two (3.0%) had ACTH-independent nodular cortical hyperplasia (NCH); Group B (bilateral adrenalectomy), 32 (47.8%) patients (F=25, M=7, median age 38 years), including two (3.0%) patients with multinodular adrenal hyperplasia, and 30 (44.8%) patients with pituitary Cushing’s syndrome. There were no differences (p=NS) between Groups A and B in age (45.813.28 vs 40.512.75 years) and in plasma cortisol levels at 8 AM (29.23.26 vs 31.25.95 g/mL). Twenty-six (38.8%) patients of Group B showed relapse of the disease 8-49 months (median 19 months) following transsphenoidal pituitary resection, external beam radiation or both, and 4 (6.0%) patients had no evidence of pitutary enlargement on CT-scan and MRI notwithstanding positive central-to-peripheral ACTH gradient on petrosal venous sampling, and subsequently underwent primary bilateral adrenalectomy. All patients underwent NCS and CT-scan prior to adrenal surgery, and moreover 58 (86.6%) patients had MRI study. Exclusive unilateral uptake and bilateral increased uptake were considered as true positive results in Groups A and B respectively. In Group A, NCS was 97.1% sensitive (one false negative result due to bilateral uptake), whereas CT-scan and MRI incorrectly showed the adrenal glands in patients with NCH, and sensitivity was 94.3% and 92.9% respectively. In Group B, NCS was 100% sensitive, CT-scan 65.6% and MRI 60.0%. In fact, CT-scan and MRI showed normal bilateral adrenal glands in 4 and 3 patients, and unilateral hyperplasia or mass in 7 and 9 patients, respectively. Overall sensitivity was 98.5% (NCS), 80.6% (CT-scan) and 75.9% (MRI). In conclusion, NCS represents the most sensitive noninvasive adrenal imaging study and should be used in all patients with confirmed biochemical diagnosis of Cushing syndrome. In our experience, MRI of the adrenal glands has not proven to be more useful than CT-scan.