Effectiveness of computed tomography attenuation values in characterization of pericardial effusion

Abstract

Objective: The aim of this study was to evaluate the effectiveness of computed tomography (CT) attenuation values in the characterization of pericardial effusion.

Methods: This study consisted of 96 patients with pericardial effusion who underwent pericardiocentesis. For further diagnostic evaluation of pericardial effusion, all the patients were assessed by thorax CT. CT attenuation values were measured from at least 5 different areas of pericardial fluid by specifying the largest region of interest. The average of these measurements was computed and considered as the CT attenuation value of the patient. The patients were classified into two groups: patients with transudative pericardial effusion and those with exudative pericardial effusion.

Results: CT attenuation values were significantly higher in patients with exudative pericardial effusion than in those with transudative pericardial effusion [14.85±10.7 Hounsfield unit (HU) vs. 1.13±4.3 HU, p<0.001]. CT attenuation values had a close correlation with the pericardial fluid albumin (r=0.829), protein (r=0.752), and LDH (r=0.708) levels; WBC count (r=0.564); protein ratio (r=0.739); and LDH ratio (r=0.689) as well as the albumin gradient (r=-0.725). A cut-off value of 4.7 HU had 80% sensitivity and 87.7% specificity for the identification of exudative pericardial effusion. In addition, a cut-off value of 6.5 HU had 71.4% sensitivity and 72.3% specificity for the prediction of cardiac tamponade.

Conclusion: In patients with pericardial effusion, CT attenuation values seem to be correlated with the characterization parameters of the fluid and may distinguish exudative pericardial effusion from transudative pericardial effusion. This parameter was also found to be a predictor of cardiac tamponade. CT attenuation values can be a useful tool in the clinical evaluation of patients with pericardial effusion.

Figure 1

(a) Contrast-enhanced axial CT scan of the heart at the level of the aortic valve in a 62-year-old female patient with loculated pericardial effusion. The mean attenuation value of the effusion (circle) was –2 HU. Pericardial fluid was demonstrated as a transudate after pericardiocentesis. (b) Contrast-enhanced axial CT scan of the heart at the level of 4-chamber view in a 19-year-old male with loculated pericardial effusion. The mean attenuation value of the effusion (circle) was 30 HU. The pericardial fluid was shown as an exudate after pericardiocentesis

Figure 2

(a) Pre- and (b) post-contrast-enhanced axial CT scan of the heart at the level of 4-chamber view in a 40-year-old female patient with circumferential pericardial effusion

Figure 3

Box plots showing the attenuation values for the transudate and exudate groups. The boxes stretch from the 25^th to 75^th percentile. The horizontal line across each box is the mean. The vertical lines with whiskers extending below and above the boxes indicate the minimum and maximum values, respectively HU - hounsfield unit.

Figure 4

Box plots showing the attenuation values for the types of pericardial effusion according to pathological characteristics. The boxes stretch from the 25^th to 75^th percentile. The horizontal line across each box is the mean. The vertical lines with whiskers extending below and above the boxes indicate the minimum and maximum values, respectively HU - hounsfield unit.

Figure 5

Correlation between CT attenuation values and pericardial fluid albumin level, protein level, LDH–albumin gradient, protein ratio, and LDH ratio. Each dot represents one patient; the straight line represents the best fit line obtained by linear regression analysis CT - computed tomography; HU - hounsfield unit; LDH - lactate dehydrogenase.