title: Influenza A (H1N1) pneumonia: HRCT findings.
abstract: OBJECTIVE
  To describe aspects found on HRCT scans of the chest in patients infected with the influenza A (H1N1) virus.
  
  
  METHODS
  We retrospectively analyzed the HRCT scans of 71 patients (38 females and 33 males) with H1N1 infection, confirmed through laboratory tests, between July and September of 2009. The HRCT scans were interpreted by two thoracic radiologists independently, and in case of disagreement, the decisions were made by consensus.
  
  
  RESULTS
  The most common HRCT findings were ground-glass opacities (85%), consolidation (64%), or a combination of ground-glass opacities and consolidation (58%). Other findings were airspace nodules (25%), bronchial wall thickening (25%), interlobular septal thickening (21%), crazy-paving pattern (15%), perilobular pattern (3%), and air trapping (3%). The findings were frequently bilateral (89%), with a random distribution (68%). Pleural effusion, when observed, was typically minimal. No lymphadenopathy was identified.
  
  
  CONCLUSIONS
  The most common findings were ground-glass opacities and consolidations, or a combination of both. Involvement was commonly bilateral with no axial or craniocaudal predominance in the distribution. Although the major tomographic findings in H1N1 infection are nonspecific, it is important to recognize such findings in order to include infection with the H1N1 virus in the differential diagnosis of respiratory symptoms.
authors.affiliation: Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Viviane Brandão
authors.initials: VB
authors.lastname: Amorim
authors.forename: Rosana Souza
authors.initials: RS
authors.lastname: Rodrigues
authors.forename: Miriam Menna
authors.initials: MM
authors.lastname: Barreto
authors.forename: Gláucia
authors.initials: G
authors.lastname: Zanetti
authors.forename: Bruno
authors.initials: B
authors.lastname: Hochhegger
authors.forename: Edson
authors.initials: E
authors.lastname: Marchiori
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000000981:diagnostic imaging*; D008168:Lung / Q000002:abnormalities; D008297:Male; D008875:Middle Aged; D011024:Pneumonia, Viral / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult