Could PET Imaging Replace AVS for Primary Aldosteronism?

Yes, there are emerging non-invasive alternatives to adrenal vein sampling (AVS), such as 68Ga-Pentixafor PET/CT scans ^[1]. However, AVS remains the accepted medical standard to determine which adrenal gland is overproducing aldosterone when planning for surgery ^[2][3]. Specialized PET scans are considered investigational or complementary tools that may be available at certain expert centers, usually when AVS is unsuccessful or not feasible ^[4][5].

If you are worried about having AVS, you are not alone. Many patients find the prospect of an invasive catheter procedure intimidating ^[6]. Here is what you need to know about why AVS is usually required, what the procedure entails, and the current clinical status of non-invasive alternatives.

Why Standard CT or MRI Scans Are Not Enough

When you are diagnosed with primary aldosteronism, your doctor will usually order a standard CT scan (or sometimes an MRI) of your abdomen to assess the anatomy of your adrenal glands and rule out large masses ^[2]. While important, these scans cannot reliably tell your care team which gland is actually causing the problem.

Standard imaging shows anatomy, not function ^[7]. A CT scan might show a nodule on your left adrenal gland, but that nodule could be completely harmless and non-functioning, while your normal-looking right gland is actually the one overproducing aldosterone ^[8]. Conversely, both glands might look entirely normal on a scan even though one is severely overactive ^[9]. Because relying on standard imaging alone has a high rate of both false-positive and false-negative results, AVS is usually needed to measure the actual hormone output directly from the veins of each gland ^[7][2].

What to Expect from AVS

AVS is an invasive procedure, but understanding it can help reduce anxiety. It is usually performed by an interventional radiologist who numbs the groin area with local anesthetic and inserts a small catheter into a vein. Using X-ray guidance, they carefully navigate the catheter to the veins draining each adrenal gland to draw blood samples ^[10]. The most common risks are minor bruising at the catheter insertion site, with very rare but serious risks including injury or rupture of the adrenal vein ^[11].

Sedation options vary widely by center and should be discussed with your care team beforehand to ensure they choose an approach that keeps you comfortable but does not interfere with the hormone results ^[6].

The Investigational Role of Specialized PET Scans

To bridge the gap between standard imaging and AVS, researchers have developed specialized PET/CT scans ^[1]. The most studied is the 68Ga-Pentixafor PET/CT scan.

Unlike AVS, which directly measures hormone levels, this PET scan uses an intravenous radioactive tracer that targets a specific receptor (CXCR4) often found on overactive adrenal cells ^[12]. While generally well-tolerated, it is a medical procedure that involves an IV injection, waiting time, and exposure to ionizing radiation from the tracer and the CT scan ^[13].

• High Predictive Value When Positive: When a 68Ga-Pentixafor PET scan clearly shows strong tracer uptake in only one gland, it can provide a strong indirect signal. In one cohort study of 82 surgical patients, a clearly unilateral PET result had a 98.2% positive predictive value compared to AVS ^[14].
• Limitations When Negative: The main drawback is that a negative or ambiguous PET scan does not definitively rule out single-gland disease. In that same 82-patient study, 26 patients (nearly a third) who were proven by AVS to have unilateral disease had a negative or bilateral PET scan ^[14].

Because of this limitation and the fact that the tracer does not measure aldosterone directly, 68Ga-Pentixafor PET/CT is not a routine replacement for AVS ^[4]. Other experimental PET tracers, such as 11C-metomidate, also show promise but have variable performance and are highly restricted to a few specialized research facilities ^[15][16].

When Might AVS Be Skipped?

In very specific situations, medical guidelines suggest AVS might be omitted and a patient can proceed directly to surgery. This exception is generally considered only for patients who are excellent surgical candidates and meet all of the following narrow criteria:

• Younger age (typically under 35 years old) ^[17]
• Spontaneous hypokalemia (low potassium without taking diuretics) ^[18]
• Marked aldosterone excess ^[18][19]
• A clear, unilateral adrenal adenoma (nodule) on a CT scan, with a completely normal-appearing gland on the other side ^[17]

Even in these cases, there is a small risk of the imaging misleading the surgical plan, so this decision requires careful, individualized discussion with a specialist ^[20].

Alternatives If You Decline AVS or It Is Unsuccessful

If you decide against AVS, or if the procedure is attempted but the radiologist cannot successfully draw blood from both veins (which happens occasionally), you are not out of options ^[10].

Depending on your overall health and goals, your team may recommend:

1. Pursuing Medical Management: Surgery is not mandatory for primary aldosteronism. You can opt for medical therapy using mineralocorticoid-receptor antagonists (like spironolactone or eplerenone) to block the effects of aldosterone, which is the standard, effective treatment for patients who do not want surgery, who are not surgical candidates, or who have bilateral disease ^[2].
2. Repeating the AVS at a high-volume specialized center with a very experienced interventional radiologist ^[21].