Use of NP-59 SPECT/CT for Lateralization in Primary Aldosteronism: A Case Report

Presentation Number: SAT 372
Date of Presentation: April 1st, 2017

Akiyo Tanabe*1, Masashi Kameyama1, Rina Owada2, Daisuke Yamada1, Haruki Kume3 and Hiroshi Kajio4
1National Center for Global Health and Medicine, Tokyo, Japan, 2Saitama Sekishinkai Hospital, 3National Center for Global Health and Medicine, 4National Center for Global Health and Medicine, Japan

Abstract

Introduction: The Endocrine Society clinical practice guidelines recommend adrenal venous sampling (AVS) as the gold standard test to distinguish between unilateral and bilateral subtypes of primary aldosteronism (PA). Except for patients younger than 35 years of age who have marked PA and a solitary unilateral apparent adenoma on CT, all patients with PA should have AVS before surgery. However, successful cannulation of the right adrenal vein is difficult and leads to high rates of failed AVS at centers with low patient volumes. Herein we describe a patient with unilateral aldosterone-producing adenoma (APA) that was confirmed by 131-I-6-betaiodomethylnorcholesterol (NP-59) single-photon emission CT/CT (SPECT/CT).

Clinical Case: A 45-year-old Japanese woman with 2 drug hypertension was recently found to be hypokalemic (serum K = 2.0 mEq/L). Laboratory testing showed: plasma renin activity (PRA) = 0.1 ng/ml/h, plasma aldosterone concentration (PAC) = 43.9 ng/dL, and urine aldosterone excretion = 44 mcg/d (urine Na 188 mEq/d). The PAC was not suppressed with the captopril challenge test or the saline infusion test, and PA was confirmed. CT scan demonstrated a low density right adrenal nodule measuring 11 x 6 mm. The right adrenal vein was visualized with multidetector CT and AVS with cosyntropin stimulation was performed. However, the serum cortisol levels in IVC and the right and the left adrenal veins (17.1, 15.1 and 122.6 mcg/dL, respectively), showed unsuccessful cannulation of the right adrenal vein. PAC levels in IVC and the right and the left adrenal veins were 63.2, 10.9 and 313.1 ng/dL, respectively. Instead of repeating AVS, a NP-59 SPECT/CT scan with dexamethasone (DEX)-suppression was obtained. The patient took oral DEX (3 mg/day for 4 days before and 2 mg/day for 7 days after NP-59 intravenous injection) to suppress cortisol production in normal adrenal gland. The patient was also treated with iodine tablets for 9 days to block thyroidal uptake of free 131-I. SPECT/CT images were obtained at 5 and 7 days after NP-59 administration. NP-59 SPECT/CT revealed intense uptake within the right adrenal gland without significant uptake in left adrenal gland. After laparoscopic right adrenalectomy, serum K, PAC and PRA were 4.3 mEq/L, 9.2 ng/dL, and 1.0 ng/mL/hr, respectively. Her blood pressure normalized without antihypertensive medications.

Conclusion: The role of NP-59 planar scintigraphy has been thought to be limited for subtype classification of PA because tracer uptake is poor in APAs smaller than 1.5 cm in diameter (sensitivity <50%). However, with the development of SPECT technology the resolution of scintigraphy has been improved. NP-59 SPECT/CT with DEX-suppression should be reconsidered as an effective test to determine the clinical significance of CT-detected adrenal nodules in patients with PA.

 

Disclosure: AT: Protocol review committee, ONO-Pharma, Investigator, ONO-Pharma. Nothing to Disclose: MK, RO, DY, HK, HK