Endocrine Abstracts

Introduction: Unilateral adrenalectomy is an effective treatment for aldosterone producing adenoma. However, after adrenalectomy, suppression of the contralateral zona glomerolura (ZG) function can lead to transient hypotension & hyperkalaemia. We present a protracted case of post-operative adrenalectomy related hypoaldosteronism.

Case: A 54-year-old hypertensive male with confirmed primary hyperaldoseronism (PRA<0.1 nm/h, aldosterone 1050 pmol/l; PRA ratio 2200) underwent a left laparoscopic adrenalectomy following confirmatory AVS and MRI in September 2014. Postoperatively, he developed acute hypotension and acute kidney injury (AKI). After discharge, he was found to have hypoaldosteronism with a PRA level 0.1 and aldosterone levels <100. He was commenced on fludrocortisone and his AKI resolved. He remained on fludrocortisone with interval measurements of his PRA, aldosterone and U&Es.

Discussion

The incidence of post-operative hyperkalaemia is approximately 16%, with 5% exhibiting prolonged hypoaldosteronism requiring mineralocorticoid replacement therapy. Possible mechanisms underlying delayed recovery include:

1) Reduced renal perfusion following normalization of blood pressure post adrenalectomy can unmask renal impairment secondary to previous aldosteronism (via hypertension or via direct effects on fibrosis/inflammation)

2) Delayed recovery of the remaining renin angiotensin- ZG function related to elevated (primary hypoaldosteronism) or supressed (secondary hypoaldosteronism) of renin levels.

It has been recommended in 2008 potassium sparing agents should be withdrawn and antihypertensives reduced. Plasma aldosterone renin levels should be measured after the adrenalectomy and on day one postoperative. However, this is not predictive of the complications described in this case as renin levels can be suppressed or elevated. In this case, this gentleman required 15 months of fludrocortisone. Predictive factors include age >53, long duration of hypertension, previous use of NSAIDs and size of adenoma. A pragmatic postoperative monitoring approach is to measure regular U&Es, aldosterone every 3-6 months with a trial reduction/ withdrawal of fludrocortisone.