Endocrine Abstracts

Background: Negative imaging in the work-up for unilateral (surgical) primary aldosteronism (PA) presents a diagnostic dilemma. Clinicians may assume bilateral disease and treat medically or may proceed to adrenal vein sampling (AVS) to try to localize a unilateral source of aldosterone secretion. However, AVS is not without cost, risk, and limited access. We describe AVS results among imaging-negative PA patients.

Methods: We identified 96 patients with PA and normal adrenal imaging who underwent AVS at a quaternary care centre from February 2008 to February 2018. Patient demographics, laboratory results, diagnostic imaging, and AVS results were retrieved. AVS lateralization was defined by an aldosterone-cortisol ratio of >3:1 from the dominant to non-dominant side. Clinical characteristics were compared for those with AVS findings of unilateral vs. bilateral disease.

Results: AVS was technically successful in 95 individuals with normal adrenal imaging (99.0%). The median age was 50 (interquartile range, 41–58) years and 53.1% were male. Hypokalemia was present in 52.6% and the mean estimated glomerular filtration rate (eGFR) was 83.5 (standard deviation, 21.1) ml/min per 1.73 m². The median aldosterone-renin ratio (ARR) was 344.1% (interquartile range, 217.0–665.9) above the assay-dependent upper limit of normal. One-third had evidence of lateralization (left in 12.6% and right in 21.1%). Subjects with unilateral PA, compared to those with bilateral disease, were more likely to be ≥40 years of age (90.9% vs 69.8%; P=0.02). Sex, ARR, eGFR, and serum potassium levels were not significantly different between groups.

Discussion: One-third of patients with normal adrenal imaging lateralized with AVS. AVS lateralization was more common in individuals aged ≥40 years. Sex, renal function, and hypokalemia were not predictive of lateralization. Older patients with normal imaging should still be considered for AVS. Future research should explore possible etiopathologies that may cause PA in young patients lacking adrenal adenomas.