Conn's Syndrome – Adrenal Adenoma (CT) Fig. 23.11a Conn's syndrome: right adrenal adenoma demonstrated by CT. Conn's syndrome is caused by either adrenal hyperplasia or an adrenal tumour, the majority of which are small adenomas. Scan (a) shows a 1 cm tumour in the right adrenal gland, lying between the inferior vena cava (IVC) and the right kidney, and a normal left adrenal gland. The tumour is of low attenuation when compared with the soft tissues. This feature is often seen in Conn's tumours. Venous sampling to measure aldosterone levels may be required to confirm the CT findings and may detect tumours too small to be visualised on CT. Significantly elevated aldosterone levels from both adrenal glands usually indicates bilateral hyperplasia. See earlier: • Normal Adrenal (CT) See also: • Conn's Syndrome