Adrenal Incidentaloma: When CT Findings Matter | UMH

An adrenal incidentaloma is a mass on your adrenal gland that nobody was looking for. Someone scanned your belly for kidney stones, back pain, or a check-up — and the radiology report mentions a “1.8 cm nodule on the right adrenal, likely benign adenoma, recommend correlation.” That sentence sends thousands of men to my clinic every year, most of them terrified the scan has found a cancer. The truth is more interesting and much more reassuring. The majority of these masses are harmless. A small but important minority are quietly producing a hormone that is wrecking your blood pressure, your sleep, your bones, or your heart — and you would never know without the right tests. A smaller minority again are early cancers that need to come out. Your job, and mine, is to sort which one you’ve got. For the full overview of how a urologist thinks about screening tests at your age, see our complete Men’s Wellness Hub. This guide walks you through exactly how I work up an adrenal incidentaloma, what the imaging numbers mean, and when surgery is the right answer.

What an Adrenal Incidentaloma Actually Is

You have two adrenal glands. They sit like small triangular caps on top of each kidney, weigh about 5 grams each, and are responsible for an outsized share of your daily physiology. The outer layer (cortex) makes cortisol (your stress hormone), aldosterone (which controls your blood pressure and potassium), and a small amount of sex hormones. The inner core (medulla) makes adrenaline and noradrenaline. Almost every adrenal incidentaloma arises from the cortex.

The word “incidentaloma” is a clinical mash-up — incidental + adenoma. It means a mass found by accident on imaging done for some other reason, typically a CT for abdominal pain, back pain, kidney stones, or trauma. Modern CT scanners are so sensitive that they now find a nodule on roughly 4-7% of adult scans, and closer to 10% in men over 70.[1] Most are not new — they have been sitting there silently for years.

Here is the breakdown of what these masses turn out to be, drawn from the largest published series and the 2023 European Society of Endocrinology / ENSAT guideline:[2]

• ~80% benign non-functioning adenomas — silent, harmless, no treatment needed.
• ~10% functioning adenomas — making cortisol, aldosterone, or catecholamines in excess.
• ~5% pheochromocytomas — medullary tumors releasing adrenaline.
• ~2-5% adrenocortical carcinoma or metastasis — the cancer fraction, almost always in masses over 4 cm.

Your odds are weighted heavily toward the benign 80%. But that does not mean you skip the workup. The whole point of finding the mass is to identify which 20% you might be in.

The Imaging Features That Change Everything

The single most useful number in your CT report is the density of the mass on non-contrast CT, measured in Hounsfield units (HU). Hounsfield units measure how much radiation a tissue absorbs — water is 0 HU, fat is around –100 HU, and most solid tissue is between 30 and 50 HU. Benign adrenal adenomas are full of lipid, so they read low on non-contrast CT.

A mass measuring less than 10 HU on non-contrast CT is nearly always a benign adenoma — the specificity is around 98%.[3] If your report mentions “lipid-rich adenoma” or “HU < 10,” your urologist will visibly relax. If it does not include a non-contrast measurement, ask for one. A contrast-only CT cannot make this distinction reliably.

The other imaging features I look for in a radiology report:

• Size. Under 4 cm is reassuring. Over 4 cm raises the cancer risk meaningfully — about 6% of masses 4-6 cm and 25% of masses over 6 cm are carcinoma.[2]
• Border. A smooth, round, well-circumscribed mass favors adenoma. Irregular margins favor malignancy.
• Homogeneity. Uniform internal texture favors benign. Necrosis, calcifications, or heterogeneous patches raise suspicion.
• Washout. If you’ve had a contrast CT, the radiologist can calculate absolute washout: how quickly contrast leaves the mass. Over 60% absolute washout (or over 40% relative washout) means adenoma. Slow washout means it could be a pheochromocytoma, carcinoma, or metastasis.
• Growth. A stable size over 12 months strongly favors benign. Growth of more than 0.5 cm in a year is a red flag.

If the non-contrast CT is equivocal — say 12 or 15 HU — the next step is usually an adrenal MRI with chemical shift imaging, which detects intracellular lipid that CT can miss. Adrenal MRI is the most accurate test we have short of histology.

The Three Hormone Tests You Actually Need

Every adrenal incidentaloma — even a small, lipid-rich one that looks textbook-benign — needs a hormone workup. The reason is that “non-functioning” on imaging is not the same as “non-functioning” biochemically. Roughly 10-15% of incidentalomas that look benign on CT are quietly producing excess cortisol, and another 1-5% are pheochromocytomas hiding in plain sight.[4] Both can damage your cardiovascular system for years before they’re identified.

The three tests I order on the first visit:

1. Overnight 1 mg dexamethasone suppression test (cortisol excess)

You take 1 mg of dexamethasone (a synthetic steroid) at 11 pm and have your blood cortisol checked at 8 am the next morning. A healthy adrenal will see the dexamethasone and shut down its own cortisol production overnight — your morning level should be suppressed below 50 nmol/L (1.8 mcg/dL). If your cortisol fails to suppress, that adrenal mass is autonomous — it is making cortisol regardless of what your brain tells it to do. This is called mild autonomous cortisol secretion (MACS) and it raises your risk of hypertension, type 2 diabetes, osteoporosis, and cardiovascular events.[2]

2. Plasma free metanephrines or 24-hour urine metanephrines (pheochromocytoma)

This screens for a pheochromocytoma — a medullary tumor releasing adrenaline and noradrenaline in bursts. Symptoms classically include episodic pounding headaches, sweating, palpitations, and high blood pressure that comes in spikes, but a third of patients have no symptoms at all. Catching one before surgery matters: operating on an undiagnosed pheochromocytoma can trigger a fatal hypertensive crisis on the table. The test is the same regardless of symptoms — order it on every incidentaloma.

3. Aldosterone-to-renin ratio (primary hyperaldosteronism)

Order this only if your blood pressure is elevated or your potassium is low. Around 1-2% of incidentalomas produce excess aldosterone — Conn syndrome — and the tip-off is hypertension that resists treatment, often combined with low potassium. The screening test is the morning aldosterone-to-renin ratio (ARR), drawn while sitting upright. If positive, an endocrinologist confirms with a salt-loading test. Renal hypertension and primary aldosteronism are the two surgically correctable causes of high BP — both worth catching.

When the Answer Is Surgery

The surgical treatment for an adrenal mass is adrenalectomy — removing the affected adrenal gland, almost always laparoscopically through three or four small abdominal incisions. Recovery is typically 2-3 weeks. The remaining adrenal gland takes over within hours, so a man with one healthy gland needs no hormone replacement long-term.

I recommend surgery when any one of the following is true:

• The mass is functioning — cortisol-secreting, pheochromocytoma, or aldosterone-secreting — regardless of size. Hormone excess is the indication; the lesion has to go.
• The mass is larger than 4 cm, even if non-functioning and benign-appearing. The risk of underlying carcinoma climbs steeply with size, and the European guideline sets 4 cm as the surgical threshold.[2]
• The mass has suspicious imaging features — irregular borders, density > 20 HU, slow washout, growth on serial scans, or heterogeneous internal texture.
• The mass grows by more than 0.5 cm between follow-up scans.

For a pheochromocytoma, surgery is preceded by 10-14 days of alpha-blockade (typically phenoxybenzamine or doxazosin) to prevent intraoperative hypertensive crisis. This is non-negotiable — taking a man with an unblocked pheochromocytoma to theatre is one of the few situations in urology where you can kill someone in minutes.

If your workup points to surgery, ask the operating surgeon two specific things: how many adrenalectomies they perform per year (volume matters — over 20 per year is the threshold for best outcomes), and whether the case will be discussed at a multidisciplinary meeting with endocrinology before the date is booked.

What Follow-Up Looks Like When We Watch and Wait

If your mass is small (under 4 cm), looks unambiguously benign on CT (< 10 HU, smooth borders), and all three hormone tests are normal, surgery is not on the table. You go into surveillance. The 2023 European guideline simplified the follow-up considerably — earlier guidance had patients returning for scans yearly for five years, which was expensive, anxiety-provoking, and not supported by outcome data.

The current approach for a clearly benign, non-functioning incidentaloma:

• No routine repeat imaging if the mass is < 4 cm and has classic benign features on the initial scan.
• Repeat imaging at 6-12 months only if any imaging feature was equivocal at baseline.
• Repeat hormone screening at 1 year, then only if your blood pressure changes, you develop diabetes, you gain unexplained weight around the trunk, or you develop osteoporosis — any of which could point to a slowly developing cortisol excess.
• Discharge from clinic at 2-5 years if everything has remained stable.

Two practical points men ask me about in clinic. First, you do not need to change your diet, lifestyle, or exercise because of an adrenal incidentaloma — the mass is not affected by what you eat. Second, your kidney function is not at risk from the adrenal mass itself. If your creatinine is rising in parallel, that is a separate issue worth investigating on its own merits (see our guide on what high creatinine means: High Creatinine Levels: Causes and When to Worry).

If you want a more structured read on which screening tests you should already be doing at your age, our 40+ Men’s Health Checklist covers the bigger picture. And for an estimate of how worrisome a specific adrenal nodule is based on your imaging and hormone results, the Adrenal Incidentaloma Risk Stratifier puts the numbers together for you. Many adrenal incidentalomas are also picked up alongside another vascular finding, which is why your urologist will usually want to know your blood pressure history at the same time — the BP & Kidney Damage Risk tool is the quickest way to gauge whether your readings are tracking into the danger zone.

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Dr. Muhammad Khalid

MBBS · FCPS (Urology) · MCPS (Gen. Surgery) · CHPE · CRSM · IMC #539472

Specialist urologist with 11+ years of clinical experience across tertiary teaching hospitals. Trained at Lady Reading Hospital and Khyber Teaching Hospital, Peshawar. Author of 5 peer-reviewed international publications in Cureus, WJSA, and AJBS. Procedural expertise: URS, PCNL, RIRS, TURP, TURBT, and major open urological surgery. Full profile →

This article is for educational purposes only and does not constitute medical advice. Always consult your physician or urologist for diagnosis and treatment decisions specific to your condition.