U032

Repeat adrenal vein sampling demonstrating bilateral aldosterone secretion after initial discordant results in the investigation of primary hyperaldosteronism, a case report

M Allum, SC Barnes, J Jackson, TM Tan, K Meeran

Abstract:

Adrenal vein sampling (AVS) is the gold standard test for distinguishing unilateral hypersecretion from bilateral hyperplasia in primary hyperaldosteronism.  The aldosterone cortisol ratio (ACR) is used to correct for variable dilution between samples.  Published guidelines vary on the interpretation of ACR ratios.  AVS results should be interpreted with caution, especially if near borderline or in the context of discordant imaging.

A 45 year old woman with longstanding hypertension and hypokalaemia was investigated for possible Conn’s Syndrome.  Aldosterone renin ratio was consistently raised and subsequent saline suppression test confirmed primary hyperaldosteronism.  CT scan showed right-sided 9mm adrenal nodule and the left adrenal gland was reported as normal.  AVS without cosyntropin infusion was then performed.   Cortisol levels confirmed appropriate cannulation.  ACR for the left adrenal vein was 15.9, compared to 3.0 on the right adrenal vein and 3.2 for the IVC.  According to Endocrine Society guidelines this could be interpreted as supporting unilateral hypersecretion from the left, as ACR left/ACR IVC >2.5 and ACR right/ACR IVC <1.  However, according to our experience and local guidelines, we apply a stricter ratio of ACR right/ACR IVC <0.5 to confirm unilateral hypersecretion.  As the ACR right /ACR IVC was 0.94 and given the discordant imaging suggesting an adenoma on the right, we remained cautious and the patient was managed with continued medical therapy.

Three years later the patient was reinvestigated due to difficulty in tolerating spironolactone.  Repeat AVS showed ACR of 14.4 in the left compared to 18.5 in the right and 3.5 in the IVC.  This now clearly demonstrated bilateral secretion of aldosterone.

This prismatic case suggests that a stricter criterion for suppression of the ACR in the contralateral adrenal should be considered.  We also conclude that AVS results can change over time, as they did here with evolving bilateral adrenal hyperplasia, and that repeat AVS is justified in cases where diagnosis is not clear-cut.

AVS 1 Jan 2011	Aldosterone (pmol/L)	Cortisol (nmol/L)	Aldosterone Cortisol Ratio (ACR)	ACR ratio to IVC
Right adrenal vein	3760	1256	3.0	0.94
Left adrenal vein	6500	410	15.9	4.97
Lower IVC	300	93	3.2
AVS 2 Oct 2013
Right adrenal vein	15000	811	18.5	5.29
Left adrenal vein	9100	630	14.4	4.11
Lower IVC	480	139	3.5