SCINTIGRAPHY OF INCIDENTALLY DISCOVERED BILATERAL ADRENAL MASSES

The purpose of this study was to determine the patterns of iodine-131 6 beta-iodomethylnorcholesterol (NP-59) imaging and the correlation wi th computed tomography (CT)-guided adrenal biopsy and follow-up in pat ients with bilateral adrenal masses, To this end we investigated a con secutive sample of 29 euadrenal patients with bilateral adrenal masses discovered on CT for reasons other than suspected adrenal disease. Ad renal scintigraphy was performed using 1 mCi of NP-59 injected intrave nously, with gamma camera imaging 5-7 days later, In 13 of the 29 pati ents bilateral adrenal masses were the result of metastatic involvemen t from lung carcinoma (5), lymphoma (3), adrenocarcinoma of the colon (3), squamous cell carcinoma of the larynx (1), and anaplastic carcino ma of unknown primary (1). Among these cases the NP-59 scan demonstrat ed either bilaterally absent tracer accumulation (in eight, all with b ilateral metastases proven by CT-guided biopsy or progression on follo w-up CT) or marked asymmetry of adrenocortical NP-59 uptake (in five), Biopsy of the adrenal demonstrating the least NP-59 uptake documented malignant involvement of that gland in five of five patients. In two patients an adenoma was found simultaneously in one adrenal with a con tralateral malignant adrenal mass. In each of these cases, the adenoma demonstrated the greatest NP-59 uptake, In 16 patients diagnosis of a denoma was made on the basis of (a) CT-guided adrenal biopsy of the gl and with the greatest NP-59 uptake of the pair (n=4), or (b) adrenalec tomy (n=2), or (c) absence of change in the size of the adrenal mass o n follow-up CT scanning performed 6 months to 3 years later (n=10). It is concluded that differential in vivo functional information provide d by NP-59 scintigraphy complements that derived from anatomic imaging and can be used in patients with bilateral adrenal masses to select w hich gland would be the best choice for further diagnostic invasive ev aluation (e.g., adrenal biopsy) or may suggest the presence of bilater al adrenal metastases in patients with incidentally discovered, bilate ral adrenal masses.