Adrenal vein sampling for aldosterone can be extremely useful in identifying whether there is a unilateral or bilateral source of aldosterone. Although cannulation of the left adrenal vein is relatively easy, it is difficult to enter the right adrenal vein. For this reason, blood samples should always be taken to determine cortisol levels, in addition to those for determining aldosterone levels, in order to confirm that the catheter tip is actually in the adrenal vein. A typical example of an adrenal vein catheterisation in a patient with an adenoma is shown in Fig. 10.8.
