The role of CTPA in investigating a patient with a pleural effusion of unknown etiology

Abstract

Purpose: Pulmonary embolism (PE) represents the 4th-5th most frequent cause of pleural effusion. Chest Computed Tomography (CT) with intravenous administration of an iodine-containing contrast material (CT IVC) is usually performed during the initial investigation of a patient with a pleural effusion of unknown etiology. The radiological protocol of the chest CT IVC in this clinical scenario is still debatable. The purpose of our study is to demonstrate whether CT pulmonary angiogram (CTPA) can reveal PE as the leading or secondary cause of pleural effusion, even if PE is not the most likely diagnosis.

Methods: This is a multicenter, prospective, observational study of adult patients with pleural effusion of unknown etiology who underwent CT IVC for the investigation of the primary cause of the effusion. The radiological protocol followed was CTPA. Demographics, medication, duration of symptoms, laboratory investigation, predisposing factors, risk assessment of PE and the characteristics of the aspirated fluid were recorded. We also documented the most likely diagnosis of the effusion prior to CTPA and the final diagnosis after the completion of work-up.

Results: Until the time of submission of this abstract 122 patients with pleural effusion of unknown etiology who underwent CTPA were registered. 28 patients out of 122 (22.9%) were diagnosed with PE. Half of the patients of this subgroup (14 out of 28 patients with PE) had an estimated Wells’ score of 0-3.5 (PE unlikely).

Conclusion: The early outcome of this study shows that a low pre-test probability for PE should not be an exclusion criterion for performing CTPA during the investigation of a patient with a pleural effusion of unknown etiology.