P1-10: Renin-aldosterone axis deficiency without frank hyperkalemia following unilateral adrenalectomy for primary aldosteronism (PA) : about 4 cases.

BACKGROUND: Aldosterone-producing adenoma is classically treated by unilateral adrenalectomy. Severe hyperkalemia, related to adrenal insufficiency, have been already reported after surgery. We describe here 4 male patients who, despite subnormal kalemia, developed a failure of the renin-aldosterone (RA) axis, resulting in a decrease in extracellular fluid volume (ECFV) following surgery

METHODS: PA diagnosis was established according to French recommendations. Unilateral adrenalectomy was performed in all. Postoperative explorations included ECFV measurement using inulin, and RA axis functionally test by orthostatic and ACTH stimulation. A decrease in ECFV with low renin level, and insufficient orthostatism-induced aldosterone production were depicted. The ACTH test demonstrated no glucocorticoid deficiency, along with responsive aldosterone secretion. The discrepancy in aldosterone response in orthostatic position versus ACTH stimulation test suggested that hypoaldosteronism primarily results from the lack of angiotensin 2 stimulation as a result of hyporeninism.

CONCLUSIONS: Following unilateral adrenalectomy for PA, the occurrence of normal-to-high kalemia prompted an evaluation of the RA system using ortho-static stimulation test rather than simply measuring baseline values and evaluating the glucocorticoid axis. When confirmed, RA axis depression causes latent hypovolemia, meaning that all treatment likely to further decrease plasma volume should be avoided, while this may at times require mineralo-corticoid substitution.