Key Points

• Chest radiography and computed tomography (CT) are the primary imaging modalities for evaluating pleural disease.
• The radiologic appearance of pleural fluid and air collections vary depending on their size, presence of loculations, and patient positioning.
• Typical imaging features of pleural masses include a peripheral location, sharp or partly sharp interface with the lung, and obtuse angles with the chest wall.
• Pleural malignancy should be suspected if multiple masses are present, or if parietal pleural thickening is greater than 1 cm, nodular, or circumferential or involves the mediastinal pleural surface.

Pleural abnormalities often are first discovered or suspected on chest radiographs. CT provides greater sensitivity in detecting and specificity in characterizing pleural disease and may help discriminate pleural, chest wall, and peripheral pulmonary processes in certain cases. The excellent spatial resolution now obtainable with multiplanar reformatting from multidetector CT scanning has further improved the CT depiction of anatomic regions more optimally evaluated by coronal and sagittal planes, such as the superior sulcus and the diaphragm. Magnetic resonance imaging (MRI) of pleural diseases provides diagnostic capabilities largely similar to those of CT, without the need for ionizing radiation. However, MRI requires greater time and expense and provides far less concomitant information about the lung parenchyma. Ultrasonography is used primarily to confirm the presence of pleural fluid and to provide imaging guidance for pleural fluid aspiration or percutaneous biopsy of pleural masses.