title: Efficacy of Computed Tomography (CT) Attenuation Values and CT Findings in the Differentiation of Pleural Effusion.
abstract: BACKGROUND
  The aim of this study was to investigate the efficacy of computed tomography (CT) findings for characterizing pleural effusions with the use of attenuation values.
  
  
  METHODS
  One hundred and twenty eight patients with pleural effusions on thoracic CT who underwent thoracentesisis within two weeks were studied. Pleural effusions were classified as exudates or transudates according to the Light's criteria. A region of interest was placed for the measurement of Hounsfield Unit (HU) values in the area of the greatest amount of effusion on each slice of the three slices used. CT features that were evaluated for distinguishing pleural exudates from transudates included pleural nodules, pleural thickening and loculation.
  
  
  RESULTS
  Thirty three (26%) of the 128 pleural effusions were transudates and 95 (74%) were exudates. The mean HU values of the exudates (8.82±7.04) were significantly higher than those of the transudates (2.91±8.53), (p<0.001). No statistically significant difference was found between transudate and exudate patients in terms of pleural thickness, pleural nodules and loculation (p>0.05).
  
  
  CONCLUSIONS
  HU values can help in differentiating exudative pleural effusions from transudative pleural effusions. Because of overlapping HU values, correlation with clinical findings is essential.
authors.affiliation: Department of Radiology, Kartal Dr Lütfü Kırdar Training and Research Hospital, Istanbul, Turkey.
authors.forename: Kadihan
authors.initials: K
authors.lastname: Yalçin-Şafak
authors.affiliation: Department of Radiology, Kartal Dr Lütfü Kırdar Training and Research Hospital, Istanbul, Turkey.
authors.forename: Neslihan
authors.initials: N
authors.lastname: Umarusman-Tanju
authors.affiliation: Department of Radiology, Kartal Dr Lütfü Kırdar Training and Research Hospital, Istanbul, Turkey.
authors.forename: Muhammet
authors.initials: M
authors.lastname: Ayyıldız
authors.affiliation: Department of Biochemistry, Kartal Dr Lütfü Kırdar Training and Research Hospital, Istanbul, Turkey.
authors.forename: Nihal
authors.initials: N
authors.lastname: Yücel
authors.affiliation: Department of Radiology, Kartal Dr Lütfü Kırdar Training and Research Hospital, Istanbul, Turkey.
authors.forename: Tamer
authors.initials: T
authors.lastname: Baysal
keywords: Exudates and Transudates; Multidetector Computed Tomography; Pleural Effusion