Unenhanced chest CT lung window image reveals that lingula, right middle lobe, and both lower lobes show patchy, peripheral, rounded, peribronchial ground-glass opacities with air bronchograms. Image source: American Journal of Roentgenology

Routine evaluation of imaging research exams by radiologists may result in a high number of incidental findings. Subsequent clinical action can result in early beneficial diagnosis or lead to harm and excessive costs resulting from evaluation of radiographically-suspicious incidental findings, according to research published online Sept. 27 in the Archives of Internal Medicine.

The frequency of incidental findings in imaging research exams and in clinical practice is common and varies significantly by imaging modality, body region and age, and clinical action can result in medical benefit to a small number of patients, explained Nicholas M. Orme, MD, from the department of radiology at the Mayo Clinic in Rochester, Minn., in an interview.

Orme and his colleagues sought to learn how often and what modalities were more associated with incidental findings and also to determine whether or not follow-up of incidental findings has positive outcomes for patients.

“We’ve seen both incidental findings picked up in a research study that led to an early diagnosis and treatment of significant disease, and we’ve seen incidental findings lead to unnecessary testing and procedures for a finding that wasn’t a disease after all,” he said. 

The researchers obtained medical records on 1,426 research participants undergoing a research imaging exam from a database of billing records from January 2004 through March 2004. Each radiology report was reviewed for incidental findings, imaging modality, body region imaged and was followed up after three years, as medical records were available for all participants through February 2007.

At follow-up, the researchers recorded demographic data and information about any clinical action performed as a result of the incidental finding, including further diagnostic imaging, referral to a subspecialist, diagnostic medical testing, invasive diagnostic procedures/biopsies, initiation of medical therapy and surgical intervention.

Following data collection, an expert panel consisting of six physicians, including four radiologists, reviewed all incidental findings generating clinical action to determine medical benefit or burden, Orme explained.

The debate continues

A total of 1,376 research participants (690 males, average age 58 years) underwent 1,426 research imaging exams. Of the exams, 39.8 percent presented with at least one incidental finding. The total number of incidental findings was 1,055; 284 exams had multiple findings. The risk of an incidental finding was found to increase significantly with age, as research participants presenting with incidental findings had an average age of 63 years. Additionally, abdomen/pelvis and thorax CT generated more incidental findings than other studies, at 61 percent and 55 percent, respectively, offered the researchers.

Of the 567 exams with an incidental finding, 6.2 percent generated clinical action, resulting in clear medical benefit in 1.1 percent and clear medical burden in 0.5 percent, said Orme, who noted that upon further review by the expert panel, the medical benefit or burden was determined to be unclear in 26 of the 567 cases.

Incidental findings are notorious for being benign, offered Orme. “I’m not surprised so many physicians chose to look at the whole clinical picture and if patient didn’t have any symptoms, chose not to look into them,” he noted, explaining that some of the findings were not suspicious and additional information was not warranted.

Despite the small number of incidental findings that were followed up, more people experienced a clear benefit than a clear burden in having their incidental finding worked up, said Orme. For many of the incidental findings presented in the research, however, “the jury is still out,” he stated.  

The authors suggested that “timely, routine evaluation of research images by radiologists can result in identification of incidental findings in a substantial number of cases that can result in significant medical benefit to a small number of patients.”

The research alluded to the fact that a majority of imaging research is done without trained radiologists reviewing films. “That’s one responsibility we have when we take these images as radiologists, is to try to look at them, and in an early fashion,” he concluded.

Incidental findings present ethical dilemmas for physicians, according to Bernard Lo, MD, of the University of California, San Francisco, in an accompanying editorial. “When planning a study, researchers need to develop a comprehensive plan for how they will respond to incidental findings, including what findings they will offer to disclose to patients,” wrote Lo, noting that Orme’s research is a step towards quantifying the impact of incidental findings.