Adrenal vein sampling (AVS) is a specialized medical procedure used to precisely diagnose certain conditions affecting the adrenal glands. These small glands, located atop each kidney, produce hormones that regulate various bodily functions, including blood pressure. AVS helps medical professionals determine if one or both adrenal glands are producing an excessive amount of a specific hormone, guiding subsequent treatment decisions.
What Adrenal Vein Sampling Is
Adrenal vein sampling is a diagnostic test designed to identify the exact source of excessive hormone production, particularly aldosterone, in individuals with primary aldosteronism. Aldosterone is a hormone that regulates blood pressure by controlling the balance of sodium and potassium in the blood and impacting blood volume. When too much aldosterone is produced, it can lead to high blood pressure and, in some cases, low potassium levels. Primary aldosteronism is a condition where the adrenal glands produce too much aldosterone, often leading to high blood pressure that is difficult to control with medication.
AVS is crucial because imaging tests, such as CT scans, may not always pinpoint the source of overproduction, especially if the overactive tissue or tumor is very small. The procedure helps differentiate between unilateral overproduction (excess hormone from one adrenal gland) and bilateral overproduction (excess hormone from both glands). This distinction guides treatment: unilateral overproduction might be treated with surgery, while bilateral overproduction is typically managed with medication. Interventional radiologists, who specialize in minimally invasive image-guided procedures, perform AVS.
Preparing for and During the Procedure
Preparation for AVS ensures accurate results. Patients fast for a few hours before the procedure, avoiding food or drink. Medication adjustments, especially for blood thinners and certain blood pressure medications, are discussed with the doctor. Adequate hydration is also important.
The AVS procedure typically occurs in an interventional radiology suite and lasts one to three hours. Patients receive local anesthesia at the catheter insertion site, usually in the groin, and light intravenous sedation for comfort. A thin, flexible catheter is inserted into a vein, often in the groin, and guided through blood vessels toward the adrenal veins.
Throughout the procedure, imaging guidance, such as fluoroscopy, visualizes the veins and ensures precise catheter placement. A contrast dye may be injected to map veins and confirm position. Once positioned, blood samples are collected from both adrenal glands and a peripheral vein for comparison. Some patients receive cosyntropin through an IV to stimulate glands, increasing hormone levels for accurate sampling. After samples are collected, the catheter is removed, and pressure is applied to the insertion site to prevent bleeding.
Understanding Potential Considerations
While AVS is generally safe, potential considerations and complications exist. Common, mild issues include bruising or soreness at the catheter insertion site, typically in the groin or wrist. Patients may experience discomfort during or after the procedure, manageable with over-the-counter pain relievers.
More serious complications, though infrequent, can include bleeding, infection, or blood vessel damage during catheter insertion. Rarely, patients may experience an allergic reaction to the contrast dye or an adrenal hematoma (blood clot). Medical staff monitor patients closely to identify and manage any issues promptly.
Recovery and Interpreting Results
Following AVS, patients move to a recovery area for observation, lying flat for a few hours to prevent bleeding at the catheter insertion site. Nurses monitor vital signs like heart rate and blood pressure to ensure stability. Patients may feel sleepy as sedation wears off. Most individuals go home the same day, but should arrange for a driver due to sedation. Resting for at least 24 hours, avoiding strenuous activities, and drinking plenty of fluids are recommended.
Collected blood samples are sent for laboratory analysis, measuring hormone levels, particularly aldosterone and cortisol, from each adrenal vein and a peripheral sample. Cortisol levels confirm successful collection from adrenal veins. Interpreting results involves comparing aldosterone-to-cortisol ratios from each adrenal gland; a significant difference indicates which gland is overproducing aldosterone. For instance, a significantly higher ratio on one side suggests a unilateral source of excess aldosterone. These findings guide treatment decisions, determining if surgery or medical management is appropriate.