CT of viral lower respiratory tract infections in adults: comparison among viral organisms and between viral and bacterial infections.
OBJECTIVE
We retrospectively compared the CT findings of consecutive viral and bacterial lower respiratory tract infections (LRTIs) to determine their imaging appearance and any definable differences among the causative viruses and between the viral and bacterial infections.


METHODS
Imaging features of LRTI caused by influenza virus, respiratory syncytial virus (RSV), parainfluenza, adenovirus, and bacteria over a 33-month period were reviewed by three radiologists blinded to clinical and diagnostic information. Individual CT features and the dominant pattern of infection were recorded for each examination. Imaging characteristics were compared among the four respiratory viruses and between viral and bacterial infections.


RESULTS
One hundred fifteen chest CT scans were analyzed (60 influenza virus, 19 RSV, 10 adenovirus, four parainfluenza virus, and 22 bacterial pneumonia LRTIs). Individual imaging findings and imaging patterns were seen in similar frequencies when we compared viral and bacterial LRTIs, with the exception of the diffuse airspace pattern, which was seen more frequently in bacterial infections. Although there was overlap in the imaging appearance of individual viruses, RSV and adenovirus tended to have characteristic imaging appearances. RSV presented with an airway-centric pattern of disease (13/19 cases [68%]) characterized by varying mixtures of tree-in-bud opacities and bronchial wall thickening, with or without peribronchiolar consolidation. Adenovirus typically appeared as multifocal consolidation or ground-glass opacity without airway inflammatory findings (7/10 cases [70%]).


CONCLUSIONS
There is considerable overlap in the imaging appearance of viral and bacterial respiratory infections. However, some characteristic differences can be seen, especially with RSV and adenovirus infections.
Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA. millerw@uphs.upenn.edu
Wallace T
WT
Miller
Timothy J
TJ
Mickus
Eduardo
E
Barbosa
Christopher
C
Mullin
Vivanna M
VM
Van Deerlin
Kevin T
KT
Shiley
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000000981:diagnostic imaging* / Q000382:microbiology; D003287:Contrast Media; D006801:Humans; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012141:Respiratory Tract Infections / Q000000981:diagnostic imaging* / Q000382:microbiology / Q000821:virology; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014777:Virus Diseases / Q000000981:diagnostic imaging* / Q000821:virology
D003287:Contrast Media; D007472:Iohexol