PURPOSE: To assess retrospectively the chest radiograph and CT findings of influenza A pneumonia and to evaluate whether pattern analysis of CT scans helps predict clinical outcome.
METHODS: Radiograph and CT images obtained at clinical presentation from 25 adult patients with confirmed H1N1 influenza pneumonia were assessed. The findings were evaluated for the presence and distribution of parenchymal abnormalities including consolidation, ground-glass opacity, nodules and reticulation. After then, the parenchymal abnormalities were classified into three patterns: cryptogenic organizing pneumonia (COP) or cellular nonspecific interstitial pneumonia (NSIP) pattern [consolidation and ground-glass opacity showing lower lung zone predominance with distribution along the subpleural lungs or bronchovascular bundles], acute interstitial pneumonia (AIP) pattern [consolidation showing patchy and extensive distribution without zonal predominance], and bronchopneumonia [combination of consolidation, ground-glass opacity, small centrilobular nodules or tree-in-bud opacity] pattern. Clinical outcome was divided into two groups on the basis of clinical course: group 1 necessitating outpatient-based treatment only or hospitalization of brief stay without mechanical ventilation and group 2 necessitating long-term hospitalization and mechanical ventilation.
RESULTS: Parenchymal abnormalities observed in decreasing order were GGO (24/25), consolidation (15/25) and small nodules (9/25). Additional findings were pleural effusion (10/25), air bronchograms (7/25), interlobular septal thickening (9/25), and tree-in-bud pattern (9/25). The abnormalities showed bilateral (22/25), peribronchovascular distribution (19/25), or lower lung zone predominance (16/25). They were classified into being COP or cellular NSIP (8/25, 32%), AIP (6/25, 24%) and bronchopneumonia (10/25, 40%) patterns. Patients with bronchopneumonia pattern had a tendency to belong to group 1 in their outcome; accounted for 62% (8/13) of group 1 responses and only 17% (2/12) of group 2 responses.
CONCLUSIONS: CT findings of Influenza A pneumonia in adults can be classified into COP/NSIP, AIP, and bronchopneumonia patterns. Patients presenting with bronchopneumonia pattern have a tendency to show good prognosis.
CLINICAL IMPLICATIONS: In the clinical settings of suspicious Influenza A pneumonia, the parenchymal lesions can be classified into several patterns including COP/NSIP, AIP, and bronchopneumonia patterns, and such pattern approach enables one to predict patient prognosis.
DISCLOSURE: The following authors have nothing to disclose: Hee Kang, Kyung Soo Lee, Ho Yun Lee, Myung Jin Chung, Chin A Yi, Tae Sung Kim
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