MON-277 Confirmatory Diagnosis of Primary Hyperaldosteronism Using Intravenous Saline Loading Test and Bilateral Adrenal Venous Sampling With ACTH Stimulation in a Patient With Low Aldosterone Renin Ratio (ARR)

Abstract Disclosure: J.P. de Leon: None. M.G. Famorcan: None. J.Z. Lacson: None. F.C. Yap: None. L.B. Mercado-Asis: None. Background: Primary aldosteronism (PA), is an endocrine disorder characterized by excessive aldosterone production leading to hypertension and hypokalemia. Diagnosis involves documentation of an elevated plasma aldosterone concentration (PAC) and a suppressed plasma renin activity (PRA), resulting in a high aldosterone-renin ratio (ARR). However, some cases can present with a low or negative ARR, complicating the diagnostic process. Clinical Case: A 51-year-old Filipino male with a 16-year history of hypertension and a family history of sudden cardiac death under age 35 was found to have PA despite a negative ARR. The patient presented with persistently elevated blood pressure despite being on triple antihypertensive therapy. Initial laboratory tests revealed a high normal serum sodium (143 mmol/L, normal range: 135-145mmol/L) and a low normal serum potassium (3.5 mmol/L, normal range: 3.5-5.0 mmol/L). Further testing showed a normal PAC (16.41 ng/dL, normal range: 6.41-29.98 ng/dL) and an unsuppressed PRA of 3.25 ng/mL/hr (>1 ng/mL/hr), yielding a negative ARR of 5.05 (<20). Given the high index of suspicion for PA, a saline infusion test was conducted which showed an increased post-infusion PAC of 62.72 ng/dL (>10 ng/dL) indicating a positive result for PA. Subsequent adrenal computed tomography (CT) imaging revealed nodular hyperplasia of the left adrenal gland. To further assess lateralization of aldosterone secretion, bilateral adrenal venous sampling (BAVS) with adrenocorticotropic hormone (ACTH) stimulation was performed. Post-ACTH stimulation adrenal vein-to-IVC cortisol gradient was 8.7:1 (>5:1) on the left and 12.2:1 (>5:1) on the right, indicating successful catheterization of both adrenal veins. Cortisol-corrected aldosterone ratio was 1.6:1 (<3:1) which is suggestive of bilateral aldosteronism with the right adrenal gland being the dominant and more contributory. The patient underwent systemic hormonal unloading (SHU) with laparoscopic right adrenalectomy with histopathological examination revealing diffuse adrenal gland hyperplasia. Postoperatively, the patient reported improved well-being and good blood pressure control with continued spironolactone and reduced dosage of antihypertensive medications. Conclusion: This case highlights the importance of comprehensive diagnostic evaluation in suspected PA cases, especially when initial screening tests yield negative or inconclusive results. Confirmatory tests, such as the saline infusion test and BAVS with ACTH stimulation, are crucial for accurate diagnosis and appropriate management. SHU with unilateral adrenalectomy to alleviate hormonal excess can be an effective treatment option, even in cases of bilateral adrenal disease to prevent long-term adverse cardiovascular outcomes. Presentation: Monday, July 14, 2025