6412 Remnant Aldosterone-producing adenoma identified with 11-C Metomidate post-adrenalectomy
Authors: Kek Peng Chin , Swee Du Soon , Meng khoo Chin , Puar Troy 
Published: October 2024

Abstract
Disclosure: P. Kek: None. D. Swee: None. C. khoo: None. T. Puar: None.
Introduction Primary aldosteronism (PA) is the most common cause of endocrine hypertension. We present a case of PA recurrence post-adrenalectomy which was localized with 11C-Metomidate PET-CT. Clinical case A 57-year-old Chinese male presented to Endocrinology in 2013 for a left adrenal incidentaloma while being evaluated for renal cyst. He had Diabetes mellitus type 2 for 1 year and hypertension for 2 years. Computed tomography intravenous pyelography in May 2013 reported a 3.8 x 4.4 x 3.5 cm left suprarenal fossa mass, containing specks of calcification. Enhancement was relatively homogeneous with pre-contrast of 9 HU. The right adrenal gland was unremarkable. His blood pressure was well controlled with nifedipine 30mg daily. He had normal serum potassium of 3.7 mmol/l, elevated plasma aldosterone of 54.4 ng/dl, and suppressed plasma renin activity (PRA) of 0.33 ug/l/hr. Primary aldosteronism was confirmed by intravenous salt-loading test with post-saline aldosterone of 26.3 ng/dl. 24-hour urinary metanephrine was normal. 1mg overnight dexamethasone was not suppressed at 89 nmol/l with low baseline DHEAs 0.76 umol/l (1.6-12.6) and adrenocorticotrophic hormone 7.2 ng/l, consistent with mild autonomous cortisol secretion. In view of the large adenoma (&gt;4cm), decision was to proceed with laparoscopic adrenalectomy without localization with adrenal venous sampling (AVS). He underwent adrenalectomy uneventfully in November 2013. Histology revealed a 5 cm adrenal cortical adenoma. One month post-surgery, there was partial biochemical success using PASO criteria: lower aldosterone level of 24 ng/dl and PRA at 0.42 ug/l/hr, while post-saline aldosterone was lower at 8.8 ng/dl. As such, spironolactone 25mg daily was started for PA. His blood pressure and potassium were well maintained subsequently. In July 2022, he was referred to another institution by primary care for evaluation of lung nodule. A CT chest done reported a soft tissue nodule in the surgical bed of the prior left adrenalectomy. An subsequent MRI done confirmed an indeterminate 0.9 cm enhancing soft tissue at the surgical bed. He was re-evaluated by endocrinologist from another institution and results were still consistent with PA with a baseline aldosterone of 31 ng/dl and PRA of &lt;0.6 ng/ml/h. In view of his previous surgery, AVS was avoided. He underwent 11C Metomidate PET-CT, which demonstrated an increase uptake by the left adrenal nodule. He proceeded with laparoscopic adrenalectomy in July 2023. Postoperative, there was complete biochemical success (PRA 6.0 ng/ml/hr, Aldosterone 1.1 ng/dl), and complete clinical cure (normal blood pressure without medications) Conclusion Incomplete resection of the adrenal glands may occur, particularly with larger adenomas. Functional imaging with 11C-Metomidate PET-CT can be useful in cases of recurrence / persistent PA post-surgery, as AVS may be risky in post-operative cases.
Presentation: 6/1/2024