Ancillary imaging observations potentially linked to the aetiology of a unilateral pleural effusion
| Aetiology | Examples of ancillary findings |
| Benign asbestos pleural effusion | Calcified pleural plaques may be present |
| Cardiac dysfunction | Usually bilateral; cardiomegaly; pericardial effusion |
| Postcardiac surgery | Temporal relationship with surgery; usually left sided |
| Traumatic | Rib fractures; signs of active bleeding on CT; high density on CT in the acute phase |
| Abdominopelvic pathology | Signs of cirrhosis; adnexal mass |