The right costophrenic angle is obliterated suggestive of an effusion on the right.

The patient had right upper quadrant pleuritic pain. A d dimer test was performed in addition to other tests to rule out biliary pathology. Elevated d dimer test prompted a CTPA test which confirmed right sided segmental PE.

A coronal CTPA image from the same case –

Pleural effusion can be a chest x-ray finding in a patient with pulmonary embolism.

Reference: https://accessmedicine.mhmedical.com/content.aspx?bookid=1944&sectionid=143516056#1136413018