NP-59 Scintigraphy for Primary Aldosteronism Lateralization in a Patient With Polycystic Kidney Disease

Abstract

A 65-year-old-male presented to the endocrine clinic for further evaluation and treatment of primary aldosteronism (PA). His past medical history was notable for polycystic-kidney-disease (PCKD) leading to a kidney-transplantation at age 48, as well as a diagnosis of PA at the age of 52. The patient had initially elected for medical management of PA; thus, PA sub-type-classification was not pursued. Despite treatment with spironolactone and potassium supplements, subsequent blood-pressure control was poor, with progressive renal failure and persistent hypokalemia. Currently, the patient was being prepared for a staged-bilateral-nephrectomy to relieve some of the mass-effect from the giant polycystic-kidneys. The upcoming surgery gave rise to the option of a concomitant adrenalectomy as a potential cure for PA. However, at this point, PA-sub-type classification was quite challenging. Anatomically, the large cysts grossly distorted the retroperitoneum, hiding the adrenal glands from view on CT imaging ( Figure A). Biochemically, adrenal-vein-sampling (AVS) seemed both technically difficult due to the distorted vascular anatomy as well as potentially risky due to the expected prolonged exposure to radio-contrast in a kidney transplant patient pre-existing advanced chronic kidney disease (CKD). Following a multidisciplinary consultation, NP-59 SPECT/CT was performed (Figure B-D). Very few case reports of PA in patients with PCKD have been reported thus far ((1)Hoorn E.J. Hesselink D.A. Kho M.M. Roodnat J.I. Weimar W. Van Saase J.L. Van Den Meiracker A.H. Zietse R. A case of primary aldosteronism revealed after renal transplantation.Nature Reviews Nephrology. 2011; 7: 55-60Crossref PubMed Scopus (8) Google Scholar). In the setting of PCKD, a diagnosis of PA may be delayed or missed entirely due to pre-existing alternative explanations for resistant hypertension and CKD. Furthermore, adrenal adenomas may be overlooked on planar imaging due to their small size and distorted abdominal anatomy associated with PCKD. In general, AVS is considered the gold-standard For PA sub-type classification, but in complex cases such as with PCKD, alternative diagnostic methods may be useful. NP-59 (I-131-iodo-cholesterol) is a marker of adrenocortical cholesterol uptake. Dexamethasone-suppression NP-59 scintigraphy has been suggested for the differentiation of PA sub-types, but its use is limited by low resolution allowing for false negatives as well as limited tracer availability ((2)Nomura K, Kusakabe K, Maki M, Ito Y, Aiba M, Demura H. Iodomethylnorcholesterol uptake in an aldosteronoma shown by dexamethasone-suppression scintigraphy: relationship to adenoma size and functional activity. J Clin Endocrinol Metab. 1990 Oct;71(4):825-830. doi: 10.1210/jcem-71-4-825. PMID: 2401712.Google Scholar). The addition of SPECT/CT over planar imaging NP-59 scintigraphy, has been shown to increase sensitivity to 82%, including the detection of aldosterone producing adenomas smaller than 1.5 cm ((3)Yen R.F. Wu V.C. Liu K.L. Cheng M.F. Wu Y.W. Chueh S.C. Lin W.C. Wu K.D. Tzen K.Y. Lu C.C. TAIPAI Study Group131I-6β-iodomethyl-19-norcholesterol SPECT/CT for primary aldosteronism patients with inconclusive adrenal venous sampling and CT results.Journal of Nuclear Medicine. 2009; 50: 1631-1637Crossref PubMed Scopus (94) Google Scholar). In our patient, NP-59 SPECT/CT clearly identified a functional left-adrenal cortical adenoma (Figures B-D). Subsequent left adrenalectomy and nephrectomy resulted in normalization of potassium levels and improved blood-pressure control allowing for a reduction in the number of his anti-hypertensive medications. Pathological evaluation identified a 3cm cortical adenoma. Thus, NP-59 SPECT/CT should remain a part of the diagnostic armamentarium, especially for challenging cases of PA sub-type classification.