Quantitative selenium-75-cholesterol imaging and computed tomography of the adrenal glands in Conn's syndrome

Six consecutive patients with biochemically proven primary aldosteronism (4 with unilateral aldosteronomas and 2 with bilateral hyperplasia) underwent imaging with 75Se-selenomethyl-nor-cholesterol (Scintadren; Radiochemical Centre, Amersham, UK) and computed tomography (CT) of the adrenal glands to aid in lateralizing unilateral aldosterone-producing adenomas (APA) and to differentiate APA from idiopathic adrenal hyperplasia (IAH). Scintadren quantitative imaging alone was successful in lateralizing the lesion in all 4 cases of unilateral APA; mean uptake by the affected adrenal gland was 0.47% of the administered dose as against 0.23% in the normal gland (P less than 0.01). The mean uptake ratio for the adenomatous as against the normal gland was 2.03 (range 1.75-2.21), which was significantly greater than the uptake ratio of 0.82 in 4 normal individuals (P less than 0.01). CT lateralized all the APAs. In the 2 cases of IAH, Scintadren uptake was bilaterally increased in one case in which CT was normal, whereas in the other case Scintadren uptakes were normal while CT showed two abnormal glands. The overall diagnostic yield for Scintadren was 83%; the figure for CT was also 83%. When the results of Scintadren imaging and CT are pooled, the accuracy in lateralizing APAs and differentiating APA from IAH as a cause of Conn's syndrome is 100%.