Adrenal Cortical Scintigraphy for Lateralization of Bilateral Adrenal Nodules in Primary Aldosteronism

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. A 73-year-old male visited the Emergency Department for weakness in both legs. He had a 20-year history of hyper-tension. At the Emergency Department, his blood pressure was high (160/100 mmHg). Routine laboratory tests revealed hypokalemia (serum potassium level, 1.9 mEq/L). Additional laboratory tests were done and his aldoster-one-renin ratio was 80.9 (serum aldosterone, 28.3 ng/dL; plasma renin activity, 0.35 ng/mL/h), which suggested primary aldosteronism (PA). Suppression tests confirmed the diagnosis; his serum aldosterone remained elevated after acute saline loading with intravenous saline (33.8 ng/dL). On abdominopelvic computed tomography (CT), bilateral adrenal nodules (right, 1.7 cm; left side, 1 cm) were detected (Fig. 1). To determine which side was functioning, bilateral adrenal venous sampling (AVS) was done, but the sampling failed to determine lateralization because it was not performed at the correct position. Therefore, we performed adrenal cortical imaging using radioiodinated I-6--iodomethyl-19-norcholesterol (NP-59) with single photon emission computed tomography-computed tomog-raphy (SPECT-CT) (Fig. 2). To block thyroid uptake of the free form of radioactive iodine, 10 drops of Lugol solution were given daily (for 1 week, beginning 2 days before NP-59 injection). For pharmacological adrenosuppression, dex-amethasone was given orally (1 mg four times a day starting 7 days before NP-59 injection and continuing until the last day of scanning). After these two preparations, Iodine-131 (I-131) NP-59 was injected intravenously. Planar NP-59 abdominal images taken on day 3 demonstrated asymmetric and focal uptake in the region of the 1.7-cm-sized nodule in the right adrenal gland, which persisted on images taken on day 6 (Fig. 2A, C). NP-59 SPECT-CT confirmed that the right adrenal nodule was functional and was responsible for the patient's laboratory results (Fig. 2B, D). Laparoscopic adrenalectomy of the right adrenal gland was performed and the pathologic result was adrenocortical adenoma. Laparoscopic adrenalec-tomy was performed via the retroperitoneal approach. The patient was placed in the full flank position on the operating table. After trocar insertion, the Gerota's fascia was opened, and the upper pole of the kidney was mobilized to expose the adrenal gland. The adrenal vein was ligated from the inferior vena cava. Then the adrenal gland was dissected off the surrounding organs. Because the patient's blood pressure was well controlled by medication, we …