Incidental imaging finding

Based on Wikipedia: Incidental imaging finding

The Accidental Discovery Problem

Imagine you go to the doctor for back pain. They order an MRI of your spine. The scan comes back, and your doctor calls with unexpected news: "Your back looks fine, but we noticed something on your adrenal gland."

You didn't know you had adrenal glands. You certainly didn't know there was something on one of them. Now what?

Welcome to the strange world of the incidentaloma—a tumor or abnormality found by accident while doctors were looking for something else entirely. The term itself is a bit tongue-in-cheek, a medical portmanteau combining "incidental" with the suffix "-oma," which typically denotes a mass or tumor. But there's nothing funny about the cascade of anxiety, testing, and difficult decisions these surprise findings can trigger.

Why This Is Happening More Often

Modern medical imaging is extraordinarily powerful. A CT scan can reveal structures smaller than a centimeter. An MRI can distinguish between different types of soft tissue with remarkable precision. This technological marvel comes with an unintended consequence: the more carefully we look at the human body, the more abnormalities we find.

And we're looking a lot.

The use of CT scans has increased dramatically over the past few decades. Emergency rooms order them routinely. Preventive health clinics offer whole-body scans to anxious patients willing to pay out of pocket. Every politician and celebrity, it seems, gets comprehensive imaging as part of their "executive physical."

The numbers are striking. About one in three cardiac MRIs—scans of the heart—turn up something unexpected. Chest CT scans show similar rates, with roughly thirty percent revealing an incidental finding. When researchers studied whole-body screening CT scans, they found lung abnormalities in fourteen percent of patients who had no symptoms whatsoever.

These aren't rare events. They're routine.

The Adrenal Gland Surprise

Let's return to those adrenal glands, since they're among the most common sites for incidental discoveries. You have two of them, small triangular organs perched atop your kidneys like little hats. They produce hormones including cortisol (which helps you respond to stress), aldosterone (which regulates blood pressure), and adrenaline (which powers your fight-or-flight response).

Between six-tenths of a percent and 1.3 percent of all abdominal CT scans reveal an unexpected mass on an adrenal gland. That might sound small, but given the millions of abdominal scans performed each year, it adds up to an enormous number of surprised patients.

Here's the crucial context: less than one percent of these adrenal incidentalomas turn out to be cancer.

Less than one percent.

So the overwhelming majority of people who receive this alarming news—"we found a mass"—have something completely benign. Often it's an adenoma, a harmless cluster of cells that will never cause any problems. Sometimes it's a myelolipoma, a tumor made of fat and blood-forming tissue that sounds frightening but is entirely innocent. Occasionally it's just a cyst, a fluid-filled sac of no clinical significance.

But that doesn't mean we can simply ignore these findings. That remaining fraction of a percent matters enormously to the people who have it.

The Diagnostic Cascade

Once an incidentaloma is discovered, a process begins that doctors sometimes call the "cascade effect." One test leads to another, which leads to another, which may lead to a biopsy, which may lead to surgery, which may lead to complications from the surgery—all for something that might never have caused any harm if left undiscovered.

For adrenal masses, clinical guidelines have evolved to navigate this treacherous territory. The first consideration is size. Masses larger than four centimeters are generally recommended for surgical removal because larger masses are more likely to be malignant. The surgery, called an adrenalectomy, involves removing the entire adrenal gland.

Smaller masses get a more nuanced approach. Doctors want to know two things: Does it look dangerous? Is it producing excess hormones?

The imaging appearance provides important clues. On a CT scan, benign adenomas typically appear less dense than surrounding tissue because they contain fat. Radiologists measure this density in Hounsfield units, named after the Nobel Prize-winning engineer who invented the CT scanner. A measurement of ten Hounsfield units or below is considered diagnostic of an adenoma—essentially confirming it's benign without needing to cut it out.

There's another clever test involving contrast dye. When you get a CT scan with contrast, the dye is injected into your bloodstream and temporarily makes various structures more visible. Adenomas have a characteristic property: they wash out the contrast dye rapidly. If fifty percent or more of the contrast medium has cleared after ten minutes, that's another strong indicator of a benign adenoma.

The Hormone Question

Even benign tumors can cause problems if they're churning out excess hormones. An adenoma that's producing too much cortisol can cause Cushing's syndrome, a condition marked by weight gain, high blood pressure, diabetes, and weakened bones. One producing excess aldosterone can cause dangerous hypertension. A pheochromocytoma—a tumor of the adrenal medulla, the inner part of the gland—can flood your system with adrenaline and related hormones, causing episodes of severe high blood pressure, rapid heartbeat, and sweating.

This is why all adrenal incidentalomas receive hormonal evaluation, regardless of how benign they appear on imaging. The workup typically includes something called an overnight dexamethasone suppression test. Dexamethasone is a synthetic steroid. In a healthy person, taking a small dose at night will suppress the body's own cortisol production by morning. If cortisol levels remain high despite the dexamethasone, that suggests the adrenal gland is producing cortisol autonomously, ignoring the normal feedback signals that should tell it to stop.

Doctors also collect a twenty-four-hour urine sample to measure catecholamines and their breakdown products, called metanephrines. These are the hormones associated with pheochromocytomas. And in patients with high blood pressure, they'll check aldosterone levels and something called plasma renin activity to look for autonomous aldosterone production.

If all the hormone tests come back normal and the imaging looks reassuring, many guidelines recommend a period of watchful waiting: repeat imaging at six, twelve, and twenty-four months, along with annual hormone testing for four years.

But here's where it gets philosophically interesting.

The Harm of Looking

Follow-up imaging and testing might seem like simple prudence. What's the harm in keeping an eye on something? The harm, it turns out, is substantial and measurable.

Those follow-up scans frequently show changes that trigger further investigation. The false-positive rate—cases where something looks concerning but turns out to be nothing—is remarkably high. Studies suggest that for every case of adrenal carcinoma detected through this surveillance process, roughly fifty patients undergo unnecessary additional workup for findings that prove benign.

Fifty to one.

Each of those fifty patients experiences anxiety. Many undergo additional imaging, with its associated radiation exposure. Some have biopsies, with risks of bleeding and infection. A few end up having surgery they didn't need. All of them spend time in waiting rooms and medical offices, burning hours they'll never get back, for a problem they never actually had.

This is the fundamental tension at the heart of modern medicine's incidentaloma problem. We can see more than ever before. But seeing something is not the same as understanding it, and understanding it is not the same as knowing what to do about it.

The Pituitary Paradox

Perhaps no organ better illustrates this dilemma than the pituitary gland. This pea-sized structure sits at the base of your brain, connected to the hypothalamus by a thin stalk. Despite its tiny size, it's sometimes called the "master gland" because it produces hormones that regulate other hormone-producing glands throughout the body.

Autopsy studies—examinations of people who died from unrelated causes—suggest that roughly ten percent of adults harbor pituitary adenomas. One in ten. These masses are almost universally "endocrinologically inert," meaning they don't produce excess hormones and don't cause any symptoms. Most are tiny. Most will never grow. The vast majority of people who have them live their entire lives unaware of their existence.

But if you happen to get a brain MRI for some unrelated reason—headaches, dizziness, an injury—and your pituitary adenoma shows up on the scan, suddenly you're a patient with a brain tumor.

The words "brain tumor" carry enormous psychological weight, even when doctors explain that it's benign and likely insignificant. You now know something about your body that you can't unknow. You'll wonder about it. You'll worry about it. You'll probably want to monitor it, which means more scans, more medical visits, more opportunities for something to look different and trigger more worry.

For larger pituitary adenomas—those exceeding one centimeter—guidelines recommend comprehensive hormonal testing. This makes sense because larger masses are more likely to be clinically significant. The workup includes measuring thyroid-stimulating hormone (TSH), prolactin, insulin-like growth factor 1 (IGF-1, which reflects growth hormone activity), cortisol, and reproductive hormones appropriate to the patient's sex.

But for the incidentally discovered small pituitary mass in a patient with no symptoms? The right answer might simply be: nothing. Leave it alone. Pretend you never saw it.

That's hard advice to follow.

Thyroid Nodules: A Case Study in Uncertainty

The thyroid gland, that butterfly-shaped organ wrapped around your windpipe, presents its own incidentaloma challenges. About nine percent of patients undergoing ultrasound examination of their carotid arteries—the major blood vessels supplying the brain—are found to have incidental thyroid nodules.

Nine percent.

Most thyroid nodules are benign. Thyroid cancer exists, but it's generally slow-growing and highly treatable. Yet distinguishing benign from malignant nodules isn't straightforward, and the consequences of getting it wrong run in both directions: unnecessary surgery for benign nodules, or delayed treatment for malignant ones.

Experts have developed ultrasound criteria that suggest malignancy. Concerning features include a solid, hypoechoic appearance (meaning the nodule appears darker than surrounding tissue because it doesn't reflect ultrasound waves as well), irregular or blurred margins, abnormal blood vessel patterns within the nodule, and microcalcifications—tiny calcium deposits that can indicate a certain type of thyroid cancer.

Current guidelines generally recommend biopsy for nodules larger than one centimeter that have concerning features. The biopsy is done with a fine needle, guided by ultrasound—a relatively simple procedure, but not without discomfort and small risks.

Interestingly, CT scans are considered inferior to ultrasound for evaluating thyroid nodules. This matters because many thyroid incidentalomas are first spotted on CT scans done for other reasons. The finding triggers an ultrasound, which triggers additional evaluation, which triggers decisions about biopsy—a cascade that began with a scan ordered for something entirely unrelated.

The Kidney Conundrum

Here's a remarkable statistic: most kidney cancers today are found incidentally. The classic presentation of kidney cancer—blood in the urine, flank pain, and a palpable mass—has become the exception rather than the rule. Instead, the typical patient has a CT scan for some other complaint and learns, to their surprise, that they have a renal mass.

Not all renal masses are cancer. Cysts are common and almost always harmless. But distinguishing a benign hemorrhagic cyst (one that has bled internally) from a renal cell carcinoma can be tricky on CT, since both can appear as dense, complex structures.

Doppler ultrasound helps here. This technology uses sound waves to detect blood flow through tissues. Kidney cancers typically have abnormal blood vessel patterns—newly formed vessels (neovascularization) and abnormal connections between arteries and veins (arteriovenous shunts). When ultrasound shows these patterns, cancer becomes more likely.

But some kidney cancers are hypovascular, meaning they have fewer blood vessels than typical tumors. These don't show the characteristic Doppler signals. For masses that don't clearly look like simple cysts but also don't show obvious signs of cancer, contrast-enhanced ultrasound provides another layer of evaluation. This technique is more sensitive than both Doppler ultrasound and CT for detecting these hypovascular tumors.

The good news is that incidentally discovered kidney cancers tend to be smaller and less aggressive than those found because they caused symptoms. Tumors less than three centimeters in diameter less frequently have aggressive histology. Finding them early, even by accident, may actually improve outcomes.

But "may" is doing a lot of work in that sentence. The natural history of small, incidentally discovered kidney tumors is still being studied. Some would never have caused harm if left alone. We're not always sure which ones.

The Spine's Many Surprises

Back pain is one of the most common reasons people seek medical care, and MRI has become a standard tool for evaluation. This has led to an explosion of incidental findings in the spine—most of which are clinically irrelevant.

Vertebral hemangiomas are among the most common. These are benign tangles of blood vessels within the vertebral body. They're present in perhaps ten to twelve percent of the population and almost never cause any problems. They light up distinctively on MRI, and once you know what they look like, they're easy to recognize.

Fibrolipomas—lipomas (fatty tumors) with fibrous areas—are another frequent finding. Tarlov cysts, fluid-filled sacs that develop around nerve roots, show up regularly as well. These cysts, named after the neurosurgeon who first described them, are usually asymptomatic and require no treatment.

The challenge is that patients often don't know this. They receive an MRI report that mentions "hemangioma" or "cyst," and they panic. The word "tumor" appears in medical terminology for hemangiomas. The word "cyst" sounds ominous even when it's not. The gap between what radiologists communicate and what patients understand can be vast and anxiety-provoking.

Arms, Hands, and the Diminishing Returns of Looking

An interesting pattern emerges when you compare incidental findings across different body regions. When doctors image the brachial plexus—the network of nerves that runs from the spine through the shoulder to the arm—they find incidental abnormalities in about seventy-two percent of symptomatic patients. Most are musculoskeletal in nature. About one in five patients with brachial plexus incidental findings ends up needing additional investigation or treatment.

But move further down the arm, past the elbow to the wrist and hand, and the picture changes dramatically. Only about one in four scans of the wrist and hand contain an incidental finding. Of these, only three percent of patients actually need additional tests or treatment. And of that three percent, almost all have benign pathology.

The closer you get to the periphery, it seems, the less likely incidental findings are to matter. Perhaps this reflects the anatomy: there's simply less variety of tissue types in the hand than in the chest or abdomen, fewer opportunities for surprises. Or perhaps it reflects selection bias in who gets imaged: people getting hand MRIs typically have specific, focused complaints, while people getting chest CTs often have vaguer symptoms that prompt broader investigation.

The Philosophical Problem

Some medical thinkers have criticized the very concept of the incidentaloma. They point out that these lesions have nothing in common except the accident of their discovery. An adrenal adenoma and a pituitary adenoma are completely different pathologically—different cell types, different behaviors, different implications. The only thing linking them is that neither was what the doctor was looking for.

This critique has merit. Lumping diverse findings under a single umbrella term may create a false sense of coherence. It may also create a false sense of threat: "incidentaloma" sounds vaguely sinister, as though anything found by accident must be dangerous.

Perhaps we should simply say these lesions were "incidentally found" and leave it at that—describing the circumstance of discovery without implying anything about their nature or significance.

But there's value in the term too. It captures a genuine phenomenon of modern medicine: our technology reveals more than we know how to interpret, and the gap between seeing and understanding creates real dilemmas for doctors and patients alike.

Living With Uncertainty

What should you do if you find yourself in this situation—the recipient of an unexpected finding from an imaging study done for something else?

First, understand that you're not alone. This is common. Millions of people have walked this path.

Second, context matters enormously. The same finding that warrants aggressive investigation in one patient might warrant nothing more than a note in the chart for another. Age, overall health, symptoms, personal and family history, the specific appearance of the finding on imaging—all of these factor into decision-making.

Third, don't be afraid to ask about the risks of further investigation, not just the risks of the finding itself. "What are the chances this will turn out to be nothing?" is a legitimate question. So is "What could go wrong if we biopsy this?" Doctors should be able to give you rough numbers, and those numbers often favor watchful waiting over intervention.

Fourth, recognize that uncertainty is inherent to medicine. We like to imagine that modern healthcare operates with scientific precision—that tests give definitive answers, that diagnoses are clear, that treatment decisions follow logically from evidence. In reality, medicine involves constant judgment calls under conditions of incomplete information. The incidentaloma is simply this truth made visible.

Finally, consider what kind of patient you want to be. Some people prefer to know everything, even if the knowledge brings worry. Others prefer to know only what's actionable, sparing themselves anxiety over findings that wouldn't change their care. Neither approach is right or wrong. But it helps to think about your preferences before you're in the situation, rather than after an unexpected finding has already disrupted your peace of mind.

The Bigger Picture

The incidentaloma phenomenon raises profound questions about the direction of modern medicine. We can now image the human body with unprecedented detail. Genetic testing can reveal variants of uncertain significance. Blood tests can detect molecules at vanishingly small concentrations. At every turn, we're generating more information.

But information is not knowledge, and knowledge is not wisdom. The challenge for medicine in the coming decades will be figuring out not just what we can detect, but what we should look for, what we should tell patients, and what we should do about what we find.

The incidentaloma, in all its accidental, anxiety-inducing glory, is a preview of this challenge. It's what happens when powerful technology meets the irreducible complexity of the human body. It's a reminder that every test has consequences beyond its intended purpose. And it's a call for humility—for doctors, for patients, and for a medical system that sometimes sees more than it understands.