Incidental findings commonly result when a sensitive imaging test such as CT or MRI is used to image organs and other body parts that have low risk for important disease. There are strong parallels in the clinical outcome of this construct to the results of intentionally screening low-risk patients with whole-body imaging, a practice that has been refuted by the American College of Radiology and challenged by the U.S. FDA owing to the low probability of identifying important disease and the high probability of downstream, low-value care [31, 32].

Incidental findings are not connected to the chief concern [1–3]. Therefore, the patient is considered low risk with respect to the incidental finding unless they happen to have a comorbid condition that coincidentally aligns with it (e.g., high-risk smoking history and incidental pulmonary nodule identified in a patient imaged for right lower quadrant pain). In most cases, an incidental finding will not be connected to a high-risk history, sign, or symptom because the imaging test is, by definition, being performed for a different indication. These factors predict the low-value care observed following the identification and management of incidental findings [1, 6, 8–15, 31, 32]. If the patient is at low risk of disease (e.g., most incidental findings, which by definition are unrelated to suspected disease) and the test is sensitive (e.g., CT or MRI), false-positive results will be common, indolent disease will be detected more often than aggressive disease, and overdiagnosis and overtreatment will dominate, all while giving the illusion of improved care through early identification. This outcome is analogous to what results from screening a low-risk population.

Although most incidental findings result from clinically indicated, diagnostic (i.e., not screening) examinations, the probability that an incidental finding is important is heavily influenced by analogous biases of screening. Consider this: an ideal screening test is inexpensive (i.e., low patient cost, low system cost), valid (i.e., few false-positives, few false-negatives), targeted (i.e., directed toward patients with highest disease prevalence), and useful (i.e., detects preclinical disease that otherwise would become clinically important, in a sufficient time to intervene with effective therapy that produces a superior outcome) [29, 30]. In the following section, the common biases of screening will be linked to incidental findings to help explain why low-value care is observed cascading from their detection [1, 6, 8–25, 28, 31–36].

Screening has several well-known, common biases [29, 30]. These biases inflate the apparent effectiveness of screening and provide insight into incidental findings management. This is because incidental findings result from inadvertently screening parts of the body at low risk for disease.

Detection of some incidental findings can improve morbidity or mortality through early detection. This is especially so if the patient coincidentally has risk factors for the detected disease (e.g., an incidental 3.2-cm solid renal mass in a patient with von Hippel–Lindau syndrome imaged with CT for suspected diverticulitis). This is because coincidental risk factors enrich the prevalence of meaningful disease and consequently the likelihood an incidental finding is meaningful. Meaningful in this context refers to the ideal result of a screening test: preclinical detection when effective treatment would produce a superior result if administered before symptom onset. However, coincidental risk factors are uncommon because, definitionally, incidental findings are unrelated to the chief concern.

Lack of evidence and incomplete understanding of the complex interplay between diagnostic and downstream risk make it difficult to determine during routine clinical practice whether pursuit of most incidental findings will produce high-value care. This uncertainty generally results in radiologists and referring practitioners erring on the side of diagnostic sensitivity and discounting the risks of collateral harm [2, 9, 16–19]. In that common context, ascribed benefit of managing an incidental finding is instinctual or by gestalt rather than evidence based. For example, benefit might be assigned to detection of a kidney or thyroid mass that was removed and confirmed to be cancer—detection of cancer seemingly proof enough that benefit has been conferred.

However, the reality is not so straightforward [1, 6, 8–25, 28, 31–36]. Numerous studies [8, 11, 12, 14, 15, 33, 36] have shown that intervention on incidental findings, including those that are cancer, can result in low-value care and cause harm (e.g., detecting a cancer that—had it not been identified—would otherwise not have affected a patient's life or detecting a cancer for which intervention does not change disease trajectory). These factors diminish the effectiveness of managing incidental findings. In addition to questionable efficacy, there also are harms, including false-positive results, need for confirmatory testing or follow-up, cost, complications of diagnosis and therapy, and acute and chronic anxiety [1, 6, 8–25, 28, 31–33].

The challenge in incidental finding management is determining which incidental findings require management and which do not. Additionally, if management is required, it must be done in a way that maximizes patient value. This is nonintuitive, requires detailed study, and necessitates incorporation of many factors beyond imaging features: patient risk, disease risk, patient preference, available therapies, harms of confirmatory diagnosis, and harms of therapy. It is complicated. Odds favor incidental finding management causing harm. There are numerous unfortunate examples in the literature. In the following section, three specific examples are provided.

Population-based studies have reported harm and low-value care resulting from the detection of incidental findings. These situations follow predictable, common, stepwise themes, tragically similar for many common incidental findings [1–3, 16–19, 21–32, 35]. Initially, there is enthusiasm about the potential for early diagnosis of cancer through detection of the incidental finding. The incidental finding is thus viewed as a secondary benefit of imaging. Guidelines and recommendations for management are developed to ensure patients receive the maximum benefit from early detection. Systems are instituted to ensure appropriate imaging and clinical follow-up. However, subsequent large, population-based studies have difficulty proving benefit—especially when viewed in the context of screening biases—and uncover harms that have been exerted on populations who were purported to be helped. The incidental finding is associated with a preponderance of false-positives, diagnosis of indolent or clinically unimportant disease, and no meaningful change to disease-related mortality. After a multiyear process and much collateral cost and harm, a fuller picture of the low-value care that resulted emerges. The initially aggressive approach diminishes, and the incidental finding becomes viewed as a harm of imaging.

In general, guidelines governing the management of incidental findings lack cost-effectiveness support that they result in high-value care. If incidental findings in low-risk patients are common and important—as indicated by incidental finding management guidelines—then argumentation might follow that broad-based screening should be performed in the general population (i.e., expand incidental finding management into population-level detection efforts). That has been tried and is harmful [10, 11, 31, 32]. One might argue the value proposition improves if the incidental finding is already detected (i.e., rather than trying to seek it). What follows are three prevalent examples—among many—in which that approach also has led to harm and low-value care.

It is increasingly recognized that incidental findings are incompletely understood, expensive, and surprisingly harmful. Rather than a benefit of imaging, they are usually a harm. They are not sought, the odds of them being important is low, and they create tremendous uncertainty and low-value care. The pragmatic challenge is what to do about it in the near and medium term. Some have wondered if certain incidental findings should not be reported at all [63]. The medicolegal environment complicates matters [2, 35, 63]. Some incidental findings are cancer. Sophisticated understanding of the biases that predict low-value care—that early detection of some cancers can produce a paradoxically worse outcome than had those cancers never been detected—is not a reasonable thing to expect of patients or the legal system in 2022; it is difficult for medical practitioners to understand. However, we (radiologists) should not simply maintain the status quo. Here are several recommendations.

First, we should heed the call to action raised by some asking us to be more aware of the harms of overdiagnosis and overtreatment cascading from the detection of incidental findings [16–19]. Incidental findings are a complication of diagnostic imaging—inadvertent harm despite positive intent—like bleeding following an image-guided biopsy. The specific harms of incidental finding management are more opaque than bleeding and harder to understand, but this simply means we should take a more active role in studying and managing them. It is our complication and our challenge to solve.

Second, we should advocate for incidental findings guidelines, especially our own but others as well, to explicitly incorporate and recommend appropriate studies to confirm they are working as intended. “Working as intended” means producing high-value care. We should expect incidental findings guidelines to emphasize the creation of high-value care rather than an exclusive or overweighted focus on maximizing diagnostic sensitivity. This is not a radiology-only dilemma. Incidental findings guidelines exist in many medical and surgical specialties, and we should work collaboratively with colleagues in those fields to promote a high-value approach.

Third, we should advocate for funding organizations to priori-tize the study of incidental finding management. We have a compelling argument. Incidental findings are ubiquitous and an enormous burden on the health care system [1, 3]. Randomized trials could be conducted in which deferral of aggressive diagnosis and management is a treatment arm. The emergence of active surveillance as a valid strategy for many cancer types is a precedent we can follow, apply, and expand on here.

Fourth, we should avoid being alarmist in our reporting. Yes, at present, we should follow the guidelines we support until stronger evidence arises, but we also should recognize that most incidental findings are not harmful if left alone in low-risk patients. Low prevalence of disease and the biases inherent to screening help explain why this is so. When in doubt about the significance of an incidental finding for which guidelines are unclear or give leeway, err on the side of minimizing it.

Fifth, because the clinical importance of an incidental finding is highly dependent on patient risk, we should pursue information technology solutions, in collaboration with referring practitioners, to make relevant risk factors more visible to radiologists (e.g., hypertension uncontrolled with multiple medications [adrenal nodule], unreported head and neck cancer [liver lesion]). In current practice, radiologists often rely on a brief historical snippet focused on the chief concern to interpret an examination. Incidental findings are definitionally unrelated to the chief concern and therefore not always informed by it.

Sixth, in our reporting, we should attempt to balance diagnostic sensitivity with other competing risks. We should understand the cascading harm that can result from management of an incidental finding and allow that potential for harm to influence our recommendations. We are still largely ignorant about which incidental findings are important and how best to manage (or ignore) them. In the years between now and a clear solution, we should do our best to minimize collateral harm to the patients we are trying to help.

Incidental findings are analogous to the results of screening tests when screening is applied to unselected, low-risk patients. They generally result in low-value and potentially harmful care. Patients with incidental findings but low risk for disease are likely to experience length bias, lead-time bias, overdiagnosis, and over-treatment that create an illusion of benefit while conferring harm. This includes incidental detection of many types of cancers that, although malignant, would have been unlikely to affect a patient's health had the cancer not been detected. Detection of some incidental findings can create high-value care, but most do not, and differentiation is often unclear at the time of identification. Higher patient- and disease-related risk increase the likelihood an incidental finding is important. Clinical guidelines for incidental findings should more deeply integrate patient risk factors and disease aggressiveness to inform management. However, lack of outcome and cost-effectiveness data lead to reflexive management strategies that create low-value, expensive, potentially harmful care. Radiology needs outcome and cost-effectiveness data to inform its management recommendations for incidental findings.