High-resolution Computed Tomography Findings from Adult Patients with Influenza A (H1N1) Virus-associated Pneumonia

Objective: The aim of this study was to assess the high-resolution computed tomography (HRCT) findings at presentation in patients diagnosed with Influenza A (H1N1) virus-associated pneumonia.

Materials And Methods: We reviewed the HRCT findings from 20 patients diagnosed with Influenza A (H1N1) and compared their HRCT scans with chest radiographs, obtained on the same day. The imaging studies were obtained 4-9 days after the onset of symptoms. The patients included 11 men and 9 women (ages 24-62 years; mean 42.7 years). All patients had a body temperature greater than 100.4 degrees F (>38 degrees C), tachypnea, and cough. Other common symptoms included diarrhea (60%) and sore throat (30%). The radiographs and HRCT scans were reviewed independently by two observers who reached a consensus decision.

Results: The predominant HRCT findings consisted of bilateral ground-glass opacities (n=12), bilateral areas of consolidation (n=2), or a mixed bilateral pattern of ground-glass opacities and areas of consolidation (n=6). The abnormalities were bilateral in all of the 20 patients, had a predominantly sub-pleural distribution in 13 patients, and had a random distribution in the remaining 7 patients. The predominant radiographic findings were consolidations. Normal radiographs were found in 4 out of the 20 patients.

Conclusion: HRCT may reveal parenchymal abnormalities in patients with Influenza A (H1N1) infection who have normal findings on radiographs. The predominant HRCT findings were bilateral, peripheral, ground-glass opacities and/or bilateral areas of consolidation. The patients who presented consolidations had more severe clinical course.