title: Paratracheal air cysts: prevalence and correlation with lung diseases using multi-detector CT.
abstract: BACKGROUND
  The purpose of this study was to determine the prevalence of paratracheal air cysts (PACs), their correlation with different lung diseases and their connection with the trachea by chest multi detector computed tomography (MDCT).
  
  
  METHODS
  We retrospectively reviewed chest MDCT images of 8240 consecutive patients obtained from January 2010 to December 2011 with a 16-detector multi-detector CT scanner. PACs were assessed for prevalence, location, level, size and the presence of visible communication with the trachea. MDCT diagnoses were classified as normal, primary or metastatic malignancies, chronic obstructive pulmonary disease (COPD), pneumonia and other lung diseases. We randomly selected 330 patients who had no visible PACs for the control group. We evaluated the associations between patients' demographic findings (age and sex), MDCT findings of lung and the presence of PACs. The findings of the PACs and control groups were compared. Statistical analysis used chi-squared test and Mann-Whitney U-test for evaluation.
  
  
  RESULTS
  PACs were presented in 301 patients (4%); 204 men and 97 women, ranging in age from 14 to 91 years (median = 57 years). There was no significant difference in the presence of PACs by age (P > 0.05). Male subjects showed higher prevalence (P = 0.005). Fifty PACs (16.6%) showed communication with the trachea or main bronchus. Although the relation between COPD and PACs was statistically significant (P < 0.001), there was no relation between primary or metastatic malignancies, pneumonia and other lung diseases and PACs.
  
  
  CONCLUSIONS
  PACs are common in MDCT and should not be misdiagnosed as pneumomediastinum. It should be kept in mind that PACs may be associated with COPD.
authors.affiliation: Department of Radiology, Faculty of Medicine, Ondokuz Mayis University, Samsun, Turkey.
authors.forename: Ahmet Veysel
authors.initials: AV
authors.lastname: Polat
authors.forename: Muzaffer
authors.initials: M
authors.lastname: Elmali
authors.forename: Ramazan
authors.initials: R
authors.lastname: Aydin
authors.forename: Adile
authors.initials: A
authors.lastname: Ozbay
authors.forename: Cetin
authors.initials: C
authors.lastname: Celenk
authors.forename: Naci
authors.initials: N
authors.lastname: Murat
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006801:Humans; D008171:Lung Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008297:Male; D008476:Mediastinal Cyst / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000706:statistics & numerical data*; D015995:Prevalence; D013902:Radiography, Thoracic / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors; D013223:Statistics as Topic; D014421:Turkey / Q000453:epidemiology; D055815:Young Adult
keywords: chronic obstructive pulmonary disease; multi-detector computed tomography; paratracheal air cyst; pneumomediastinum