Chest CT Angiograms to Diagnose Pulmonary Embolism Twice as Likely to Find Other Pathology
By Fran Lowry
Medscape Medical News
November 23, 2009 — Chest computed tomography angiograms (CTAs) to evaluate patients for acute pulmonary embolism in the emergency department are more than twice as likely to find an incidental pulmonary nodule or adenopathy as they are to find a pulmonary embolism, according to the results of new research published in the November 23 issue of the Archives of Internal Medicine.
"Small pulmonary nodules on chest CT scans could indicate bronchogenic carcinoma; however, these lesions are much more likely to be benign," William B. Hall, MD, from the University of North Carolina at Chapel Hill, and colleagues write. "Incidental findings of pulmonary nodules can be a source of great anxiety for patients and often generate multiple follow-up radiographic studies and other diagnostic interventions."
The aim of this study was to determine the prevalence and management implications of such incidental findings.
The investigators reviewed the results of 589 pulmonary CTAs that were ordered in the emergency department of a large academic tertiary care hospital that had 50,000 visits annually.
The mean age of the patients was 53 years (range, 34 – 72 years), and 63% were women.
The investigators report that pulmonary embolism was found in 55 CTAs (9%) and that 195 patients (33%) had findings indicative of other diagnoses.
A total of 141 patients (24%) had a new incidental finding that required clinical or radiologic follow-up.
Pulmonary nodules were the most common incidental finding and were found in 127 patients (22%). Of these, 73 were a new finding.
"Using current clinical guidelines, follow-up [CT] or another procedure would be recommended for 96% of patients with new incidental pulmonary nodules," the authors note.
In addition, new adenopathy requiring follow-up was found in 51 patients (9%).
The authors note that the primary limitation of their study is that it was carried out at a single tertiary care center, and therefore results may not be generalizable to other settings. The retrospective study design, which could have introduced bias in patient selection, is another limitation.
They conclude that systematic approaches to determining clinical risk and higher yield indications for CTA are recommended during assessments of acute pulmonary symptoms in the emergency department.
"Primary care physicians should become familiar with recommended approaches for evaluation of pulmonary nodules," the authors add, "because increasing use of CTA in the acute setting will lead to the discovery of a large number of these lesions."
In an accompanying editorial, Ami Schattner, MD, from Kaplan Medical Center, Rehovot, Israel, called this an important study.
"These findings highlight the abundance of incidental asymptomatic findings, outnumbering [pulmonary embolism] by a factor of 2.5, and may prompt us to critically examine some of the problems associated with the proliferating use of CTA in [pulmonary embolism]," he writes.
These problems include exposure to radiation and contrast during CTA. Abnormal renal function and allergy to contrast material make the procedure risky for patients with these conditions, and the radiation risk is considerable, particularly in women, younger patients, and all patients who have repeated examinations.
"The many patients in whom a symptomatic pulmonary or thoracic disease is revealed by the CTA may seem a compelling reason to support the test," Dr. Schattner writes. "However, the data reported by Hall et al strongly suggest that most of the patients have common conditions, and the differential diagnosis of dyspnea or chest pain can be made by clinical methods and simple ancillary tests such as a good-quality (e.g., not portable) chest radiography and electrocardiography."
Dr. Schattner concludes that CTA should be reserved for inpatients or patients with indeterminate findings on ventilation/perfusion scans, abnormal findings on chest radiography, discordant findings, or unusual presentations such as those compatible also with aortic dissection.
"Expected advances in scanning techniques such as single photon emission [CT ventilation/perfusion] scintigraphy are likely to further reduce the number of nondiagnostic studies and help swing the pendulum back to a more balanced evaluation of suspected cases of [pulmonary embolism]," he writes.
Dr. Hall and Dr. Schattner have disclosed no relevant financial relationships.
