SAT-071 Usefulness of NP-59 SPECT/CT for Lateralization in Primary Aldosteronism

Abstract

Introduction: Adrenal venous sampling (AVS) is recommended for subtype diagnosis of primary aldosteronism (PA). However, successful cannulation of the right adrenal vein (R-AV) is difficult and leads to failed AVS in some cases. Even in successful AVS, results are sometimes discordant with other clinical findings. Herein we describe two patients 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: Case 1 was a 45-year-old Japanese woman with hypertension and hypokalemia (serum K = 2.0 mEq/l). Plasma renin activity (PRA) = 0.1 ng/ml/h, plasma aldosterone concentration (PAC) = 43.9 ng/dl, and urine aldosterone excretion (uAldo) = 44 mcg/d (urine Na 188 mEq/d). PA was confirmed by the saline infusion test. CT scan showed a low density 11 mm right adrenal nodule. Although the R-AV was visualized with multidetector CT, AVS with cosyntropin stimulation showed unsuccessful cannulation of the R-AV; the serum cortisol (C) levels in IVC, the R-AV and the left adrenal veins (L-AV) were 17.1, 15.1 and 122.6 mcg/dl, respectively. Case 2 was a 47-year-old Japanese woman with hypertension and hypokalemia (serum K = 2.8). PRA = 0.8, PAC = 56.9, and uAldo = 34 (urine Na 226). PA was confirmed by the captopril challenge test. CT scan demonstrated a low density 16 mm right adrenal nodule. AVS with cosyntropin stimulation showed successful cannulation of both adrenal vain (the C levels in IVC, the R-AV and the L-AV were 20.9, 930 and 1040, respectively), however the result was inconclusive with lateralized ratio 2.6 (PAC levels the R-AV and the L-AV were 2814.3 and 1229.8, PAC/C in the R-AV and the L-AV were 3.0 and 1.2, respectively). Instead of repeating AVS, NP-59 SPECT/CT scan with dexamethasone (DEX)-suppression were obtained in those cases. The patients 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 in both cases. After laparoscopic right adrenalectomy, serum K, PAC and PRA were normalized. Their blood pressure normalized without antihypertensive medications. Conclusion: The role of NP-59 planar scintigraphy has been thought to be limited for subtype diagnosis of PA because sensitivity is not high. 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.