Background: The etiology of exudative pleural effusion (EPE) is challenging in clinical practice, with malignancy often being suspected. Computerized tomography (CT) is reported to have a high sensitivity and specificity for determining etiology, especially in cases of suspected malignant disease and preparation for medical thoracoscopy (MT).

Aims: To investigate the role of CT in the detection of malignant pleural disease before a more invasive approach in patients with EPE of undetermined etiology.

Methods: Between November 2020 and December 2022, a retrospective review of MT procedures was conducted at the University hospital centre Zagreb. Forty-two patients with EPE of undetermined etiology underwent chest CT scan with contrast. CT report was evaluated for signs of malignancy by an independent radiologist. 

Results: Patohistological diagnosis of malignancy was determined in 29 (69 %) cases, predominantly: mesothelioma 15 (35,7 %), non-small cell lung cancer 9 (21,4 %), non-Hodgkin lymphoma 3 (7,1 %) and metastatic breast cancer 2 (4,8 %). Non-malignant causes of pleural effusion were 1 case of (2,4 %) amyloidosis and inflammatory pleuritis in 12 (28,6 %) cases. CT with malignant findings was reported in 26 cases with a sensitivity of 68.9 % and specificity of 53.8 %. Of the 16 CT scans without malignant characteristics, 9 (56,3 %) cases were false negative, and 7 (43,7 %) were reported with no signs of malignancy.

Conclusion: Although our study shows lower CT sensitivity and specificity for diagnosing pleural diseases than other studies, CT still represents a necessary diagnostic tool in pleural space evaluation and preparation for MT.