High aldosterone levels in the renal capsular vein from the left aldosterone-producing adenoma on adrenal venous sampling.

Aldosterone-producing adenomas may drain blood into an alternative pathway but for the adrenal vein. The presence of alternative venous drainage could be assumed by contrast-enhanced computed tomography or venogram during adrenal venous sampling. Sampling in the alternative drainage veins and demonstrating elevated aldosterone levels could help in diagnosing aldosterone-producing adenoma.