title: Ultrasound in peripheral pulmonary air-fluid lesions. Color Doppler imaging as an aid in differentiating empyema and abscess.
abstract: BACKGROUND
  The aim of this study was to reevaluate the clinical significance of sonographic appearances, in particular the application of color Doppler ultrasound imaging, in discriminating peripheral air-fluid lung abscess from empyema.
  
  
  METHODS
  We retrospectively studied patients who had had peripheral air-fluid lesions due to empyema or lung abscess and who had undergone color Doppler ultrasound and grayscale ultrasound examinations between January 2003 and October 2007. A total of 34 patients with confirmed lung abscess and 30 patients with empyema were identified. The four sonographic characteristics observed and analyzed were the wall characteristics of the lesions (wall width, luminal margin, outer margin, and chest wall angle), split pleura sign, internal echogenicity (suspended microbubble sign, complex-septated effusions, and passive atelectasis), and identification of color Doppler ultrasound vessel signals in pericavitary lesions (consolidation or atelectasis).
  
  
  RESULTS
  Among the sonographic characteristics, complex-septated effusions and passive atelectasis were specific for empyema, but the sensitivity was only 40% (n = 12 of 30) and 47% (n = 14 of 30), respectively. The identification of color Doppler ultrasound vessel signals in pericavitary consolidation was the most useful and specific for identifying lung abscesses. In our series, if we define the identification of color Doppler ultrasound vessel signals in a pericavitary consolidation as a predictor for peripheral lung abscess, we can achieve sensitivity, specificity, positive predictive value, and negative predictive value of 94%, 100%, 100%, and 94%, respectively.
  
  
  CONCLUSIONS
  Color Doppler ultrasound is a powerful tool for differentiating the peripheral air-fluid abscess from empyema, with high specificity and without any risk.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Hung-Jen
authors.initials: HJ
authors.lastname: Chen
authors.affiliation: Department of Internal Medicine, China Medical University Beigang Hospital, Yunlin, Taiwan.
authors.forename: Yang-Hao
authors.initials: YH
authors.lastname: Yu
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Chih-Yen
authors.initials: CY
authors.lastname: Tu
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Te-Chun
authors.initials: TC
authors.lastname: Hsia
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Kuen-Daw
authors.initials: KD
authors.lastname: Tsai
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Chuen-Ming
authors.initials: CM
authors.lastname: Shih
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan. Electronic address: hsuwh@mail.cmuh.org.tw.
authors.forename: Wu-Huei
authors.initials: WH
authors.lastname: Hsu
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D015331:Cohort Studies; D003937:Diagnosis, Differential; D016724:Empyema, Pleural / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008169:Lung Abscess / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011336:Probability; D001261:Pulmonary Atelectasis / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution; D018615:Ultrasonography, Doppler, Color