Table 4.

Signs differentiating atelectasis and pneumonia

Parameter	Atelectasis	Pneumonia
Air bronchograms and vessels	Crowded, parallel	± Normal (expanded, normal or crowded)
Air bronchograms	Static (~6% dynamic), absent (longstanding resorptive atelectasis)	Dynamic (~62%) and static, fluid
Abscesses, empyema, necrosis	Absent	May be present
Pleural line	Normal	Thickened, irregular
Lung sliding	Normal, abolished in massive atelectasis	Abolished
Mediastinal shift	May be present, in most cases towards atelectasis	If present, rather away from pneumonia
Elevation of diaphragm, narrowing of intercostal spaces	May be present	Rather absent
Margins	Well defined most of time	Blurred/irregular, sometimes well defined
Decrease in consolidation after drainage of pleural fluid	Present in compressive atelectasis	Absent or small in degree
Pleural fluid septations or gas	Mostly absent	May be present
Echogenicity of pleural fluid	Mostly anechoic	May be echogenic