title: Occult pneumothoraces in Chinese patients with significant blunt chest trauma: radiological classification and proposed clinical significance.
abstract: BACKGROUND
  An occult pneumothorax (OP) is a pneumothorax not seen on a supine chest X-ray (CXR) but detected on abdominal or thoracic computed tomography (CT) scanning. With the increasing use of CT in the management of significantly injured trauma patients, more OPs are being detected. The aim of this study was to classify OPs diagnosed on thoracic CT (TCT) and correlate them with their clinical significance.
  
  
  METHODS
  Retrospective analysis of prospectively collected trauma registry data. Total 36 (N=36) consecutive significantly injured trauma patients admitted through the emergency department (ED) who sustained blunt chest trauma and underwent TCT between 1 January 2007 and 31 December 2008 were included. OP was defined as the identification (by a consultant radiologist) of a pneumothorax on TCT that had not been detected on supine CXR. OPs were classified by laterality (unilateral/bilateral) and location (apical, basal, non apical/basal). The size of pneumothoraces, severity of injury [including number of associated thoracic injuries and injury severity score (ISS)], length of hospital stay and mortality were compared between groups. The need for tube thoracostomy and clinical outcome were also analysed.
  
  
  RESULTS
  Patients with bilateral OPs (N=8) had significantly more associated thoracic injuries (median: 2 vs. 1, p=0.01), higher ISS (median: 35 vs. 23, p=0.02) and longer hospital stay (median: 20 days vs. 11 days, p=0.01) than those with a unilateral OP (N=28). Basal OPs (N=7) were significantly larger than apical (N=10) and non-apical/basal Ops (N=11). Basal OPs were associated with significantly more associated thoracic injuries (median: 2 vs. 1, p=0.01), higher ISS (median: 35 vs. 25, p=0.04) and longer hospital stays (median: 23 days vs. 17 days, p=0.02) than apical Ops, which had higher ISS (median: 35 vs. 25, p=0.04) and longer hospital stays (median: 23 days vs. 15 days, p=0.02) than non-apical/basal OPs. Non-apical/basal OPs were associated with more related injuries (median: 2 vs. 1, p=0.02) than apical OPs. All apical and non-apical/basal OPs were successfully managed expectantly without associated mortality.
  
  
  CONCLUSIONS
  This TCT classification of OP is proposed to help clinicians to decide on subsequent management of the OP. Basal OPs are significantly larger in size, and both basal and bilateral OPs are associated with higher severity of injury and longer hospital stay. These groups of patient may benefit from prophylactic tube thoracostomy instead of conservative treatment. On the other hand, apical and non-apical/basal groups is smaller in size, less severely injured and thus can be successfully managed expectantly.
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Chinese University of Hong Kong, the Prince of Wales Hospital, Shatin, New Territories, Hong Kong, Special Administration Region. leekalok2909@yahoo.com.hk
authors.forename: Ryan K L
authors.initials: RK
authors.lastname: Lee
authors.forename: Colin A
authors.initials: CA
authors.lastname: Graham
authors.forename: Janice H H
authors.initials: JH
authors.lastname: Yeung
authors.forename: Anil T
authors.initials: AT
authors.lastname: Ahuja
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Rainer
mesh_terms: D044466:Asian People / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D033162:Incidental Findings; D015601:Injury Severity Score; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D011030:Pneumothorax / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000209:etiology; D012189:Retrospective Studies; D013898:Thoracic Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000453:epidemiology; D013907:Thoracostomy / Q000706:statistics & numerical data*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014949:Wounds, Nonpenetrating / Q000150:complications / Q000000981:diagnostic imaging / Q000453:epidemiology