SCINTIGRAPHIC EVALUATION OF CLINICALLY SILENT ADRENAL MASSES

We studied 229 patients with abnormal adrenal anatomy depicted by CT w ho were without biochemical evidence of endocrine dysfunction using th e presence of(131)I-6 beta-iodomethyl-norcholesterol (NP-59) adrenal g land uptake as an index of differential adrenal function in the evalua tion of the clinically ''silent'' adrenal mass lesion. Methods: NP-59 (1 mCi) was injected intravenously with posterior and lateral abdomina l images obtained 5-7 days postinjection. Results: One-hundred and fif ty-nine of 185 patients with unilateral adrenal enlargement on CT had scintigraphic evidence that the mass represented a functioning (NP-59 avid) but not hypersecretory, (biochemically normal) adrenal cortical adenoma (concordant imaging pattern). Forty-one of 44 patients with in tra-adrenal neoplasms were depicted on scintigraphy as decreased or ab sent NP-59 accumulation on the side of the adrenal mass (discordant im aging pattern). In this study, sensitivity was 71% (41 of 58 patients; 95% confidence interval (CI), 58% to 88%); specificity was 100% (171 of 171 patients:; 95% CI, 95% to 100%) and accuracy was 93% (212 of 22 9 patients; 95% CI, 88% to 96%). Conclusions: These data confirm our e arlier observations that the functional information depicted by scinti graphy complements the morphological evaluation by CT and in the absen ce of hormonal dysfunction, the presence of concordant CT and I-131-NP -59 scans are characteristic of functioning, but not hypersecretory, b enign adrenocortical adenomas. Conversely, discordant CT and I-131-NP- 59 scans are suggestive of nonfunctioning, space-occupying, adrenal le sions.