Gamma camera imaging of bilateral adrenocortical hyperplasia and adrenal tumors in the dog.

Gamma camera imaging of the adrenal glands was done in 8 dogs with hyperadrenocorticism and 4 normal dogs given intravenous injections of 131I-19-iodocholesterol. In normal dogs, both adrenal glands could be visualized separately, and there was no difficulty in distinguishing among the images of normal glands, hyperplastic glands, and functional adrenal tumors. In addition, gamma camera imaging enabled the correct surgical site to be selected for removal of adrenal tumors. Hyperadrenocorticism was diagnosed in 8 dogs by evaluation of urinary 17-hydroxycorticosteroid (OHCS) excretion rates, urinary 17-OHCS and plasma 11beta-OHCS RESPONSES TO DEXAMETHASONE SUPPRESSION OF ENDOGENOUS ADRENOCORTICOTROPIN (ACTH) secretion, and plasma 11beta-OHCS response to intravenous administration of ACTH. Base line 17-OHCS excretion increased in 5 of the 8 dogs. Plasma 11beta-OHCS concentrations were not decreased by dexamethasone administration in the 4 dogs subsequently found to have adrenal tumors; however, there was an exaggerated increase in plasma 11beta-OHCS concentration after administration of ACTH in 3 of the 4 dogs which had bilateral adrenocortical hyperplasia.