Adrenal computed tomography and NP-59 usefulness for diagnosing aldosterone-producing adenomas and idiopathic hyperaldosteronism in primary hyperaldosteronism

Objectives Two major causes of primary aldosteronism are aldosterone-producing adenomas (APA) and idiopathic hyperaldosteronism (IHA). In this study, we attempted to determine the role of NP-59 in identifying APA prior to adrenalectomy, especially when diagnostic computer tomography (CT) is equivocal. Methods We performed a retrospective analysis in patients with a clinical diagnosis of primary aldosteronism. The medical records of 36 patients were reviewed, which included 25 patients who had received adrenalectomy. All patients underwent adrenal CT alone or a combination of adrenal CT and NP-59 prior to surgery for the subtyping of primary aldosteronism, based on the protocols established in our institution. The accuracy of the adrenal CT and NP-59 findings was determined by a comparison with the pathologic findings and postoperative outcomes. Results Twenty-three patients received unilateral adrenalectomy under the diagnosis of APA. The diagnoses were based on CT findings in 11 patients and on CT and NP-59 findings in 12 patients. The results of pathology were adrenal cortical adenoma in these 23 patients and the positive predictive value was 100%. Blood pressure and potassium levels significantly improved after surgery in these patients (p < 0.01). Serum biochemistry and adrenal size of the limbs and bodies of patients with IHA were not significantly different from those of patients with APA. Conclusion For the subtyping of primary aldosteronism, the imaging modality of adrenal CT alone or the combination of adrenal CT and NP-59 adrenal scan has a high positive predictive value for APAs. We suggest that all patients undergo an adrenal CT as their initial study, after confirming the diagnosis of primary aldosteronism, and to use NP-59 when adrenal CT findings are atypical or inconclusive. Lateralization by this modality prior to adrenalectomy can reduce unnecessarily invasive examinations such as adrenal venous sampling and also provide excellent treatment outcomes.