Adrenal Venous Sampling (AVS) is a specialized diagnostic procedure used to assess hormone production from the adrenal glands. This minimally invasive test involves collecting blood samples directly from the veins that drain the adrenal glands. The goal is to precisely measure hormone levels, particularly aldosterone, to identify the source of excessive production.
Understanding Why AVS is Performed
Adrenal Venous Sampling is used to diagnose primary aldosteronism, a condition characterized by excessive aldosterone production by the adrenal glands. Aldosterone is a hormone that regulates blood pressure and electrolyte balance, and too much of it can lead to high blood pressure and low potassium levels. Primary aldosteronism is a common cause of high blood pressure, affecting between 5% and 10% of all patients with hypertension.
This procedure helps determine if the excess aldosterone is coming from one adrenal gland (unilateral production) or both (bilateral production). While imaging tests like CT scans can show tumors or enlarged glands, they cannot definitively tell which gland is overproducing the hormone. AVS is considered the gold standard for pinpointing the exact source, which directly influences the appropriate treatment strategy. If the overproduction is unilateral, surgical removal of the affected adrenal gland may be a curative option for hypertension. If both glands are involved, medical management with aldosterone-blocking medications is typically the recommended approach.
Preparing for Adrenal Venous Sampling
Preparing for Adrenal Venous Sampling involves several steps. Patients will receive specific instructions regarding dietary restrictions, usually involving abstaining from food and drink for several hours before the procedure. It is important to discuss all current medications with the doctor, as certain blood pressure medications, diuretics, or blood thinners may need to be adjusted or temporarily stopped days or weeks in advance.
Patients are typically advised to maintain normal sodium intake before the procedure and to ensure their potassium levels are within a normal range, with potassium supplements prescribed if needed. Initial consultations and preliminary tests, such as blood tests to check complete blood count, electrolytes, and kidney function, are usually conducted to confirm suitability for AVS. Since light sedation is used, arranging for someone to drive the patient home after the procedure is necessary.
The AVS Procedure
The Adrenal Venous Sampling procedure typically takes place in an interventional radiology suite and can last up to two hours. Patients receive a local anesthetic to numb the groin area where a small incision will be made, along with conscious or light sedation to promote relaxation and minimize discomfort. A catheter is inserted into a vein, usually in the groin, and guided through the blood vessels using X-ray imaging, also known as fluoroscopy.
A contrast dye is injected through the catheter to help visualize the adrenal veins on the X-ray, which may cause a brief warm sensation. Once the catheter is precisely positioned in the veins of each adrenal gland, blood samples are collected from both the right and left adrenal veins, as well as from a peripheral vein like the inferior vena cava. While the procedure is generally not painful due to anesthesia, patients might feel some pressure during catheter insertion or movement. Some centers may also administer a medication like cosyntropin through an IV drip to stimulate the adrenal glands, which can help ensure adequate hormone levels for sampling.
After the AVS Procedure
Following the Adrenal Venous Sampling procedure, patients are moved to a recovery area for monitoring, usually for two to four hours. During this time, nurses will regularly check vital signs like heart rate and blood pressure as the effects of the sedative wear off. Patients may experience mild discomfort or bruising at the catheter insertion site in the groin, which can be managed with gentle pressure or over-the-counter pain relief.
Activity restrictions are in place for about 24 to 72 hours post-procedure, including avoiding strenuous exercise, heavy lifting, driving, or making significant decisions. The collected blood samples are sent to a laboratory for analysis, with results typically becoming available within about a week. An endocrinologist will then interpret these results, which compare aldosterone and cortisol levels from each adrenal vein to peripheral samples, to determine if the primary aldosteronism is unilateral or bilateral. This information guides treatment decisions.