Endocrine Abstracts

It is now well established that unilateral autonomous aldosterone secreting tumour (AST) in contrast to bilateral adrenal hyperplasia (BAH) - are corrected by surgery. The optimal method of pre-operatively defining a unilateral autonomous AST still remains controversial. There is agreement that adrenal scanning techniques are often unreliable or misleading. The aim of the current study was to analyse if a random aldosterone:renin (AR) ratio (after stopping anti-hypertensive medications), adrenal imaging (CT or MRI and nuclear medicine scanning) and adrenal vein sampling would accurately localise a unilateral autonomous AST.

We retrospectively analysed 23 subjects (14 females, 9 males) who were referred to our department over the last 4 years due to them having concurrent hypokalaemia and hypertension. Eleven subjects were diagnosed of having a unilateral autonomous AST (confirmed by histology) and 13 subjects had BAH (no evidence of tumour on adrenal imaging). All eleven subject with AST had a random AR ratio >2000. In contrast, only 4/13 BAH subjects had a random AR ratio > 2000. A MRI/CT accurately predicted an adrenal mass in 10/11 AST subjects. Among the 11 subjects with AST, 7 underwent adrenal venous sampling prior to surgery. All seven lateralised to the side of the AST. Six AST subjects underwent selenium/idocholesterol scanning but 4/6 localised the tumour. Among the 13 subjects with BAH, 6 underwent adrenal vein sampling. All six subjects showed no evidence of lateralisation. Four of these subjects had an iodocholesterol scan that revealed bilateral adrenal uptake of radioactive material.

We have demonstrated that (1) random A:R ratio >2000, (2) the presence of a tumour on adrenal imaging and (3) lateralisation of aldosterone secretion from adrenal venous sampling positively located an AST. In hypokalemic hypertensive subjects, larger numbers of subjects are needed to evaluate the role of nuclear imaging.