A physician is evaluating the recent diagnostic workup of a male patient in his early fifties presenting with treatment-resistant hypertension and persistent hypokalemia. The patient is currently prescribed maximum tolerated doses of amlodipine, valsartan, and chlorthalidone. His blood pressure in the clinic is mm Hg.
Initial laboratory evaluation revealed a serum potassium level of mEq/L. The plasma aldosterone concentration (PAC) was ng/dL, and the plasma renin activity (PRA) was ng/mL/hr. Following an intravenous infusion of liters of normal saline over hours, the PAC remained elevated at ng/dL (normal ng/dL).
Subsequent cross-sectional imaging of the abdomen with a dedicated adrenal protocol CT scan demonstrated a -cm, lipid-rich adenoma in the left adrenal gland. The right adrenal gland appeared morphologically normal.
To further guide management, adrenal venous sampling (AVS) was performed under cosyntropin stimulation. The results are as follows:
| Source | Cortisol (g/dL) | Aldosterone (ng/dL) |
|---|---|---|
| Inferior vena cava | ||
| Right adrenal vein | ||
| Left adrenal vein |
Based on these findings, which of the following is the most appropriate next step in management?
- Initiation of spironolactone therapyAnswer
- BLeft laparoscopic adrenalectomy
- CBilateral laparoscopic adrenalectomy
- DRepeat adrenal venous sampling
- EInitiation of dexamethasone therapy
Answer
In patients over years of age with confirmed primary aldosteronism, cross-sectional imaging (CT or MRI) is insufficient to direct surgical therapy because non-functioning adrenal incidentalomas are highly prevalent. Therefore, Adrenal Venous Sampling (AVS) is the gold standard required to differentiate a unilateral aldosterone-producing adenoma from bilateral idiopathic adrenal hyperplasia.
Interpreting AVS requires a systematic approach:
1. Confirm cannulation: The cortisol step-up from the IVC to the adrenal veins must be (or with cosyntropin). Here, the right gradient is and the left is , confirming proper cannulation.
2. Correct for dilution: Calculate the aldosterone-to-cortisol ratio for each side. Right = . Left = .
3. Determine lateralization: Calculate the Lateralization Index (LI) by dividing the dominant side ratio by the non-dominant side ratio. .
An LI confirms a unilateral source, whereas an LI indicates bilateral hypersecretion. Because this patient's LI is , he has bilateral idiopathic adrenal hyperplasia. The -cm nodule on the left is a non-functioning incidentaloma. The optimal management for bilateral disease is medical therapy with a mineralocorticoid receptor antagonist, such as spironolactone or eplerenone.