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Table 5 Other signs described in pleural effusion [8, 37, 38]

From: Lung ultrasound—a primary survey of the acutely dyspneic patient

Signs Cause Significance
Quad sign Pleural effusion Shape of effusion collection
Spine sign Large effusion Large effusion allowing visualisation of the spine
Plankton sign Blood, fibrin Hemothorax, exudate
Air-fluid level Air Air within effusion
Jellyfish sign Compressive atelectasis No consolidation of underlying lung
Sinusoid sign Jellyfish sign in M-mode No consolidation of underlying lung
Suspended microbubble sign Air within lung abscess Distinguish lung abscess from empyema