Rationale and Objectives
The primary objective of this study was to compare computed tomography (CT) volumetric analysis of pleural effusions with thoracentesis volumes. The secondary objective of this study was to compare subjective grading of pleural effusion size with thoracentesis volumes.
Materials and Methods
This was a retrospective study of 67 patients with free-flowing pleural effusions who underwent therapeutic thoracentesis. CT volumetric analysis was performed on all patients; the CT volumes were compared with the thoracentesis volumes. In addition, the subjective grading of pleural effusion size was compared with the thoracentesis volumes.
Results
The average difference between CT volume and thoracentesis volume was 9.4 mL (1.3%) ± 290 mL (30%); these volumes were not statistically different ( P = .79, paired two-tailed Student’s t -test). The thoracentesis volume of a “small,” “moderate,” and “large” pleural effusion, as graded on chest CT, was found to be approximately 410 ± 260 cc, 770 ± 270 mL and 1370 ± 650 mL, respectively; the thoracentesis volume of a “small,” “moderate,” and “large” pleural effusion, as graded on chest radiograph, was found to be approximately 610 ± 320 mL, 1040 ± 460 mL, and 1530 ± 830 mL, respectively.
Conclusions
CT volumetric analysis is an accessible tool that can be used to accurately quantify the size of pleural effusions.
A pleural effusion is a pathologic accumulation of fluid in the pleural space. It is a common finding, which can occur in response to a variety of insults, including infection, malignancy, pulmonary embolism, connective tissue disease, congestive heart failure, cirrhosis, and trauma . Although the presence of a pleural effusion is nonspecific, associated findings such as cardiomegaly, consolidation, and lung masses often suggest its etiology .
Pleural effusions can be diagnosed by routine chest radiography, ultrasonography, computed tomography, and magnetic resonance imaging . Even in cases where pleural effusions are diagnosed on physical examination alone, imaging is often warranted to further characterize the pleural effusion and/or estimate its size. Although ultrasound is well-suited for characterizing pleural effusions, computed tomography (CT) is superior in evaluating the size of pleural effusions . In addition, CT can be used to determine the attenuation of a pleural effusion and to visualize reactive pleural thickening or enhancement, which can provide clues to the nature of a pleural effusion .
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Materials and methods
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Table 1
Subject Enrollment: Inclusion and Exclusion Criteria
CT, computed tomography.
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Results
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Discussion
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Table 2
Pitfalls in Pleural Effusion Tracing
Pitfall Effect Comments Accidental inclusion of adjacent soft tissue Most commonly occurs with collapsed lung and mediastinal structures. Results in overestimation of pleural effusion. IV contrast helps differentiate fluid from adjacent soft tissue. Multiplanar reformats can also help in defining the anatomy. Tracing in a nonoptimal plane Tracing in a nonoptimal plane can be challenging and is often prone to error. The optimal plane is the plane where the pleural effusion can be smoothly traced without discontinuity. Motion and beam hardening artifacts Artifacts can obscure pleural fluid boundaries. Motion artifact is frequently worst near the diaphragms, whereas beam hardening is frequently worst near the apices. Minimize artifacts with optimal CT scanning technique. Complex or loculated pleural effusions Complex pleural effusions can be tedious and time-consuming to trace. More prone to tracing error. May require multiple traces to fully analyze a multicomponent pleural effusion.
CT, computed tomography; IV, intravenous.
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