Case Presentation
A 65-year-old man 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 the age of 48 years and a diagnosis of PA at the age of 52 years. The patient had initially elected for medical management of PA; thus, PA subtype 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 subtype classification was quite challenging. Anatomically, the large cysts grossly distorted the retroperitoneum, hiding the adrenal glands from view on computed tomography (CT) imaging (Fig. A). Biochemically, adrenal vein sampling seemed both technically difficult because of the distorted vascular anatomy and potentially risky because of the expected prolonged exposure to radiocontrast in a kidney transplant patient with preexisting advanced chronic kidney disease. After a multidisciplinary consultation, 131I-iodocholesterol (NP-59) single-photon emission computed tomography (SPECT)/CT was performed (Fig. B-D).
Fig.
A, A computed tomography (CT) coronal image. B, NP-59 scintigraphy. C and D, NP-59 single-photon emission CT/CT.
What is the diagnosis?
Answer
Unilateral aldosterone-producing adenoma in a patient with PCKD. Very few case reports of PA in patients with PCKD have been reported thus far.1 In the setting of PCKD, a diagnosis of PA may be delayed or missed entirely because of preexisting alternative explanations for resistant hypertension and chronic kidney disease. Furthermore, adrenal adenomas may be overlooked on planar imaging because of their small size and distorted abdominal anatomy associated with PCKD. In general, adrenal vein sampling is considered the gold standard for PA subtype classification; however, in complex cases, such as with PCKD, alternative diagnostic methods may be useful. NP-59 is a marker of adrenocortical cholesterol uptake. Dexamethasone-suppression NP-59 scintigraphy has been suggested for the differentiation of PA subtypes; however, its use is limited by low resolution, allowing for false negatives and limited tracer availability.2 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 In our patient, NP-59 SPECT/CT clearly identified a functional left-adrenal cortical adenoma (Fig. 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 antihypertensive medications. Pathological evaluation identified a 3-cm cortical adenoma. Thus, NP-59 SPECT/CT should remain a part of the diagnostic armamentarium, especially in challenging cases of PA subtype classification.
Disclosure
The authors have no multiplicity of interest to disclose.
Acknowledgment
We thank Prof. Yodfat Krausz for all her help and guidance.
Footnotes
Editor’s Note: Submissions to “Visual Vignettes” are welcomed. Please submit online via the Journal’s Editorial Manager site.
References
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