VENOUS SAMPLING

The right adrenal vein (RAV) typically drains directly into the right posterolateral aspect of the suprarenal inferior vena cava (IVC), situated between the T11 and L1 vertebral levels. Compared to the left adrenal vein, anatomical variations are common. Supernumerary veins are present in approximately 1% to 10% of cases; these may drain into the right renal, phrenic, or hepatic veins. In such cases, the central caval drainage usually remains intact. Variant drainage occurs in about 1%–8% of patients, where a single adrenal vein drains into an accessory hepatic vein, often associated with large accessory hepatic veins. The presence of a large accessory hepatic vein should prompt suspicion of abnormal RAV drainage.

The left adrenal vein normally drains into the phrenicoadrenal trunk, with the ostium reliably located on the cephalad surface of the mid-left renal vein at approximately the left lateral border of the spine. Rare variations, such as duplications or direct drainage into the IVC or left renal vein without a phrenicoadrenal trunk, occur in about 1% of cases.

Most PA patients have either bilateral hyperplasia, managed with lifelong MR blockade, or a unilateral aldosterone-producing adenoma (APA), treated with adrenalectomy. Accurate diagnosis to distinguish between IHA and unilateral APA is essential for proper treatment. Although AVS with cortisol and aldosterone measurement is recommended, it is underused worldwide due to misconceptions about its difficulty, invasiveness, and risk, despite evidence of its importance. The lack of standardized protocols and clear interpretation criteria also limits its use. As a result, many patients are denied potentially curative surgery or undergo unnecessary adrenalectomy, risking removal of a normal gland.

• None specific

• Hold antimineralocorticoid therapy for 4–6 weeks before the procedure; prefer a1-adrenergic receptor blockers and some calcium-channel blockers as alternatives
• Peripheral α1-adrenergic receptor blockers (eg, doxazosin mesylate) and/or long-acting dihydropyridine or nondihydropyridine calcium channel blockers (eg, diltiazem) can be used, while mineralocorticoid receptor antagonists are withdrawn because these agents minimally affect renin secretion
• Continue potassium supplementation aiming for normalization of serum potassium levels
• Perform the procedure with conscious sedation unless contraindicated
• Consider stimulation with cosyntropin (synthetic ACTH) to increase aldosterone secretion and improve sampling selectivity; some prefer no stimulation
• Initiate cosyntropin infusion at 50 mg/hour 30 minutes before the procedure and continue until sampling confirmation
• Achieve prophylactic heparinization with a 3000–5000-unit IV bolus
• Hypokalemia (potassium level < 3.5 mmol/L) must be corrected with oral or intravenous potassium supplementation before AVS because it decreases aldosterone secretion, thus potentially masking unilateral aldosterone production

Supine

• Use a renal double curve (RDC) catheter to select the right adrenal vein (RAV), or other suitable wall-seeking catheters (e.g., 4–5-F Cobra, Mikaelsson, Simmons 1)
• Gently sweep the RDC catheter from superior to inferior at various right posterolateral positions in the suprarenal IVC to engage the venous ostium, indicated by resistance and catheter tip upturn
• Perform a venogram to characterize the vessel after engagement
• If blood cannot be aspirated from the catheter, advance a coaxial microcatheter into the vein for sampling
• Distinguish adrenal glandular patterns from small hepatic veins and tributaries; remember glandular, triangular, and stellate configurations versus reticular hepatic sinusoid patterns
• For left adrenal vein sampling, the same catheter used for right venography can be employed, or a Simmons 2 catheter can be introduced into the IVC to select the left renal vein, then engaged to find the phrenicoadrenal trunk
• Slowly withdraw the catheter until engagement with the trunk causes an upward jump; confirm with a venogram
• Avoid deep catheterization into the phrenic vein peripheral to the adrenal inflow
• Use a Simmons 3 catheter if the orifice is unusually far from the IVC
• Collect 4 mL blood samples from each location (peripheral sheath, RAV, left phrenicoadrenal trunk), transfer to heparin plasma (green-top tube), and freeze
• Optionally, remove the catheters during rapid cortisol analysis to confirm sampling location
• Some practitioners perform simultaneous sampling to reduce variation; however, sequential sampling with stimulation is often sufficient
• Confirm successful sampling if cortisol–peripheral cortisol ratios exceed 3:1 from each side; if not, repeat sampling

If the right adrenal vein (RAV) cannot be cannulated or if blood samples cannot be obtained from the vein, we typically take blood from the inferior vena cava (IVC), positioning the catheter slightly above the expected RAV location based on CT images. However, samples from this position may not be diagnostic. Some experts recommend using the cortisol-corrected aldosterone ratio between the left adrenal vein (LAV) and the IVC (A/C ratio of LAV to A/C ratio of IVC) to determine laterality when RAV cannulation fails

• Groin hematoma, occurring in 3%–4% of cases
• Haematoma
• Infarction
• Adrenal vein thrombosis
• Perforation

• None specific

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