Fluid bronchogram sign

The fluid bronchogram sign can be seen on chest CT or ultrasound as the presence of fluid attenuation material within respiratory bronchioles with surrounding collapsed or consolidated lung.

The presence of this sign suggests endobronchial obstruction as a precipitating cause for consolidation/collapse . This can result from a number of processes:

• foreign body aspiration (children)
• endobronchial tumors
• infection (including aspergillus)
• mucus plugging

Radiographic features

Importantly, this sign is not visible on plain radiographs since collapsed lung and bronchial fluid is indistinguishable in density.

Ultrasound

Anechoic tubular structures representing fluid-clogged bronchi are seen within relatively echogenic collapsed lung. The absence of Doppler flow confirms that these are not vessels, but airways.

CT

Contrast enhanced CT is required to differentiated tubular low attenuation representing fluid bronchograms from vessels. CT has the added benefit of localizing the possible cause or level of endobronchial obstruction.