Adrenal Incidentalomas: How to Evaluate and When Surgery Is Needed

An adrenal incidentaloma is a lump in the adrenal gland that you didn’t know you had-found by accident during a CT scan or MRI done for something else, like back pain or a car accident. It’s more common than you think: about 1 in 50 people over 50 will have one, and nearly 1 in 14 people over 70. Most of these lumps are harmless. But a small number can be dangerous if they make too much hormone or turn out to be cancer. The real challenge isn’t finding them-it’s knowing which ones need action and which ones can be left alone.

What Exactly Is an Adrenal Incidentaloma?

The adrenal glands sit on top of each kidney. They make hormones like cortisol (for stress), aldosterone (for blood pressure), and adrenaline (for fight-or-flight). An adrenal incidentaloma is any adrenal mass larger than 1 centimeter that shows up on imaging done for another reason. It’s not a diagnosis-it’s a finding. About 80% of these masses are benign, non-functioning adenomas. That means they don’t make hormones and won’t cause symptoms. The other 20%? They’re the ones that matter.

Some produce too much cortisol, leading to weight gain, high blood sugar, and muscle weakness-even if you feel fine. Others make adrenaline, which can cause sudden spikes in blood pressure, sweating, or heart palpitations. Rarely, they’re cancerous. Adrenocortical carcinoma is rare, but when it happens, it’s serious. Metastatic cancer from breast, lung, or melanoma can also spread to the adrenal glands. That’s why every incidentaloma needs a careful look.

Step 1: Rule Out Pheochromocytoma First

Before you do anything else, you must rule out a pheochromocytoma. This is a tumor that makes too much adrenaline and noradrenaline. If you don’t catch it before surgery, you could have a deadly surge in blood pressure during anesthesia. That’s not theoretical-it’s happened. Studies show that up to 4% of adrenal incidentalomas are pheochromocytomas.

The test is simple: measure plasma-free metanephrines or 24-hour urinary fractionated metanephrines. These are breakdown products of adrenaline. If they’re elevated, you’ve got a pheochromocytoma. No exceptions. Even if the tumor looks small and benign on the scan, if the metanephrines are high, you need to treat it before anything else.

And here’s the catch: if you’re on certain medications-like antidepressants, decongestants, or even some blood pressure pills-your results can be falsely high. Your doctor needs to know everything you’re taking. If the test is borderline, it might need to be repeated or confirmed with a different method.

Step 2: Check for Cortisol Overproduction

Next, you test for autonomous cortisol secretion. This is trickier. You might not feel sick, but too much cortisol over time increases your risk of diabetes, heart disease, and bone loss. About 5% of adrenal incidentalomas cause this. It’s called subclinical Cushing’s syndrome.

The standard test is the 1-mg dexamethasone suppression test. You take a pill at night. The next morning, your cortisol level is checked. If it’s above 1.8 μg/dL (or 50 nmol/L), it suggests your adrenal gland isn’t responding to the body’s normal feedback system. That’s a red flag.

But here’s the problem: some people naturally have higher cortisol. A new test, urinary steroid metabolomics, is now showing better accuracy. It looks at patterns of cortisol breakdown products in urine. A 2023 study found it was 92% accurate at spotting cortisol overproduction-much better than the old test. More centers are starting to use it, but it’s still not widely available.

If cortisol is high, you need to think about surgery-even if the tumor is small. Studies show that removing the tumor improves blood pressure, blood sugar, and even mood in these patients.

Step 3: Screen for Aldosterone

If you have high blood pressure or low potassium, check for aldosterone. This hormone makes your kidneys hold onto salt and water, raising blood pressure. About 4% of incidentalomas are aldosterone-producing adenomas. That’s more common than you’d think.

The test is simple: measure plasma aldosterone concentration and plasma renin activity. The ratio between them tells you if aldosterone is too high. If it is, you might have primary hyperaldosteronism. That’s treatable-with medication or surgery. Many patients see their blood pressure drop significantly after removing the tumor.

Step 4: Read the Imaging Like a Pro

Not all tumors look the same on a CT scan. The first scan you get is usually an unenhanced CT. It measures density in Hounsfield units. If the tumor has a value below 10 HU, it’s almost certainly a benign adenoma. That’s because benign adenomas have lots of fat inside, which shows up as low density.

But if the tumor is above 10 HU, you need more info. Is it irregular? Does it have uneven edges? Is it growing? A tumor larger than 4 cm has a higher chance of being cancer. At 6 cm or more, the risk jumps to 25%. That’s why size matters.

Some tumors are clearly not adenomas. Myelolipomas have fat and blood cells-they’re harmless. Cysts are fluid-filled and usually benign. But if the tumor looks patchy, has calcifications, or is growing fast (more than 1 cm per year), it’s suspicious. That’s when you refer to a specialist.

When Do You Operate?

Surgery isn’t always needed. But it’s required in three cases:

1. Functional tumors-any tumor making too much cortisol, adrenaline, or aldosterone. Size doesn’t matter. If it’s making hormones, remove it.
2. Tumors larger than 4 cm-even if they’re not making hormones. The risk of cancer jumps sharply after this size.
3. Suspicious imaging-irregular shape, rapid growth, or signs of invasion into nearby organs.

For pheochromocytomas, surgery isn’t just about removing the tumor-it’s about preparing for it. You need alpha-blockers for at least 7 to 14 days before surgery to prevent dangerous blood pressure spikes. This isn’t optional. Skipping this step can kill you.

For cortisol-producing tumors, surgery often reverses metabolic problems. For aldosterone tumors, blood pressure improves in up to 80% of cases. And for cancer? Surgery is the only chance for cure-if it hasn’t spread.

What If It’s Benign and Not Making Hormones?

If your tumor is under 4 cm, looks like a typical adenoma on CT, and hormone tests are normal-you’re probably fine. No surgery. No follow-up scans. No medication.

That’s right. No routine monitoring. Many patients panic and ask for yearly scans. But studies show that if the tumor is small and looks benign, the chance it turns cancerous is less than 1%. Repeated scans just expose you to radiation and cost money. The American College of Radiology and Endocrine Society both say: if it’s low risk, leave it alone.

There’s one exception: if you’re unsure. Maybe the CT was unclear. Maybe your cortisol was borderline. In those cases, a repeat scan in 6 to 12 months is reasonable. But if it doesn’t change, you’re done.

Why This Matters: The Real Risk Is Under- or Over-Treatment

The biggest danger isn’t missing cancer-it’s operating on a harmless tumor. Adrenalectomy is usually done laparoscopically and is safe. But you still lose an adrenal gland. You might need lifelong hormone replacement. You’ll have surgical risks. And if the tumor was benign, you’ve been through all that for nothing.

On the flip side, missing a pheochromocytoma or early cancer can be deadly. That’s why the evaluation has to be thorough. It’s not about being paranoid. It’s about being precise.

Specialized centers get this right more often. A 2023 survey found that 92% of patients treated at dedicated adrenal centers were satisfied with their care. At general hospitals? Only 68%. Why? Because these centers have endocrinologists, radiologists, and surgeons who talk to each other every day. They know which tests to order, how to interpret them, and when to act.

What’s Changing in 2026?

The guidelines are evolving. The Endocrine Society is updating its recommendations based on new data. One big change: if your post-dexamethasone cortisol is above 5.0 μg/dL, surgery is now strongly recommended-even if you don’t have classic Cushing’s symptoms. The evidence shows these patients have higher rates of heart disease and death.

Also, urinary steroid metabolomics is becoming more accessible. It’s not perfect, but it’s better than the dexamethasone test. Some insurance companies are starting to cover it. And for tumors that are 3 to 4 cm? More centers are now doing biopsies or molecular testing to check for cancer markers before deciding on surgery.

The message is clear: adrenal incidentalomas aren’t a one-size-fits-all problem. They’re a puzzle. Each piece-hormones, size, imaging, growth rate-has to fit together. Get it right, and you avoid unnecessary surgery. Get it wrong, and you risk your health.

Don’t panic if you’ve been told you have one. But don’t ignore it either. Ask for the right tests. Make sure your doctor knows the latest guidelines. And if you’re unsure, go to a center that sees these cases often. Your adrenal glands might be small-but the stakes aren’t.