Chest CT pegs inhalation anthrax at Virginia facility

CT imaging has moved to the forefront of radiology’s response to the recent bioterror attacks using anthrax (Bacillus anthracis) spores delivered via the U.S. mail. A group of radiologists in the Washington, DC, area is using the modality to successfully screen patients for advanced inhalation anthrax disease.

On October 19, a 56-year-old man arrived at the emergency department of the Inova Fairfax Hospital in Fairfax, VA, complaining of flu-like symptoms (fever, chills, chest heaviness, and a minimally productive cough of three days’ duration). He identified himself as a postal worker, and the emergency-room physicians ordered a posteroanterior (PA) projection chest x-ray and a chest CT study.

The initial evaluation in the ER revealed a widened mediastinum on the chest radiograph, and an order to rule out anthrax was sent to the radiology department. Dr. Donald Cerva Jr., the radiologist on duty, noted that the patient’s x-ray showed hilar and mediastinal masses. He also observed left-side hilar adenopathy and a small left infiltrate.

The patient was then referred for a chest CT exam. The procedure was conducted on a LightSpeed (GE Medical Systems, Waukesha, WI) spiral scanner. No contrast was used, and a standard 7-mm slice thickness chest protocol was employed.

Cerva observed a profuse and slightly hyper-attenuating paratracheal, anteroposterior (AP) window, subcarinal, hilar, and azygo-esophageal recess lymphadenopathy. In addition there was diffuse mediastinal edema, bilateral pleural effusions, bibasilar airspace disease, more pronounced on the left, and thickened peribronchial tissue (seen best on lung windows).

The following morning, a second postal worker, also a 56-year-old man, who worked at the same distribution center as the first patient, was admitted to Inova with a three-day history of progressively worsening headache, muscle aches, and a slight cough. Because he was linked epidemiologically to the index case of inhalation anthrax at the institution, a chest radiograph and chest CT scan were ordered.

Dr. Elise Berman was the radiologist on duty, and was aware of the earlier findings made by Cerva. She reviewed portable AP chest films and observed a widened mediastinum, bilateral hilar masses, bilateral pleural effusion, and perihilar airspace opacities.

A noncontrast CT scan was performed on the patient using the institution’s standard chest protocol. Berman found a profuse and slightly hyper-attenuating paratracheal, AP window, subcarinal, hilar, and azygo-esophageal recess lymphadenopathy similar to what Cerva had observed a few hours earlier in the first patient.

She also saw diffuse mediastinal edema, bilateral pleural effusions, and thickened peribronchial tissue. In this patient, however, bibasilar airspace disease was more pronounced on the right.

Cerva said noncontrast CT provided a good baseline for the studies.

"Contrast can always be done later if needed," she said. "Also, one patient developed some degree of renal insufficiency, which would be another reason to do a noncontrast scan," he said.

Berman offered this advice to fellow radiologists who may be called on to rule out anthrax: "If there’s any suspicion of inhalation anthrax, order a PA and lateral chest x-ray as well as a CT workup of the patient."