Unenhanced chest CT lung window image of patient with swine flu. Image source: American Journal of Roentgenology

Researchers using CT scans have found that patients with severe cases of the H1N1 virus are at risk for developing severe complications, including pulmonary emboli, according to a study to be published online  today in the American Journal of Roentgenology.

The study, performed at the University of Michigan Health Service, included 66 patients diagnosed with the H1N1 flu. The researchers formed two study groups—one of which consisted of 14 patients who were severely ill and required intensive care unit (ICU) admission; and the other consisted of 52 patients who were not severely ill and did not require ICU admission.

All 66 patients underwent chest x-rays for the detection of H1N1 abnormalities. Ten patients from the ICU group and five patients from the largely outpatient group, underwent CT scans, according to the authors.

“Pulmonary emboli were seen on CT in five of 14 ICU patients," said lead author Prachi P. Agarwal, MD, radiologist at the University of Michigan in Ann Arbor.

"Our study suggests that patients who are severely ill with H1N1 are also at risk for developing pulmonary emboli, which should be carefully sought for on contrast-enhanced CT scans," she said.

"With the upcoming annual influenza season in the United States, knowledge of the radiologic features of H1N1 is important, as well as the virus's potential complications. The majority of patients undergoing chest x-rays with H1N1 have normal radiographs. CT scans proved valuable in identifying those patients at risk of developing more serious complications as a possible result of the H1N1 virus, and for identifying a greater extent of disease than is appreciated on chest radiographs," said Agarwal.

The study will be published in the December issue of the American Journal of Roentgenology.