Assessment of computed tomography for the diagnosis of exudative and transudative pleural effusion

Introduction: The basic computed tomography (CT) characteristics of pleural effusion (PE) were analyzed, and the association between demographic factors and prominent CT findings with different types of PE was assessed. The individual CT characteristics and Light’s criteria for exudative PE were also evaluated. In addition, a cutoff for attenuation values of CT scans for exudative PE was determined. Methods: A cross-sectional study among 92 participants with PE was carried out at Bir Hospital, Kathmandu, Nepal. The χ2 test, logistic regression analysis, and diagnostic statistics were calculated. The ethical clearance was obtained from the institutional review committee of Institutional review board of National Academy of Medical Sciences (NAMS), Bir Hospital (Ref. 876/076/77). Results: The study examined 92 cases of PE, with 78.3% occurring in males and the majority affecting individuals aged 55–74 years old. Results showed that on CT scans, pleural thickening [odds ratio (OR): 13.89, 95% CI: 4.96–38.86, P < 0.05], pleural nodules (OR: 12.72, 95% CI: 2.64–61.18, P < 0.05) and loculations (OR: 13.46, 95% CI: 4.03–44.89, P < 0.05) were significantly associated with exudative PE. Of these, pleural nodules had the highest specificity (96.4%) and positive likelihood ratio (9), whereas pleural thickening had the highest sensitivity (70.3%). When using the criterion “pleural fluid Lactate Dehydrogenase concentration as positive if it was over two-thirds of the upper limit of normal serum Lactate Dehydrogenase,” the CT scan had a positive likelihood ratio of 22.52. The study also found that an attenuation value ≥9.70 HU could indicate an exudative PE (area under the curve: 0.80, 95% CI: 0.70–0.90, P < 0.05). Conclusion: The CT characteristics, such as pleural thickening, pleural nodules, and loculations, were more likely to be present in exudative PE. In addition, the attenuation values of PE could also determine its nature as either exudate or transudate, with an attenuation value of >9.70 HU indicating an exudative PE.