A lung abscess is best defined by which imaging feature?

A lung abscess is best defined by which imaging feature?

• A. An air-fluid level within a cavity
• B. Diffuse interstitial edema
• C. A simple consolidation
• D. A large pleural effusion

Answer: (A)

A cavitary lesion in the lung parenchyma that contains an air-fluid level is the imaging hallmark of a lung abscess. In infection, tissue liquefies and forms a cavity; pus settles in the dependent portion while air from the bronchi enters, creating a distinct air-fluid interface. On chest X-ray or CT, this appears as a thick-walled cavity with a dependent fluid level. This distinguishes it from simple consolidation, which is just homogeneous opacity without a cavity or fluid level. It also differs from diffuse interstitial edema, which shows interstitial markings and edema rather than a defined cavity. And it’s not a large pleural effusion, which collects in the pleural space with a meniscus rather than as a parenchymal cavity.

A cavitary lesion in the lung parenchyma that contains an air-fluid level is the imaging hallmark of a lung abscess. In infection, tissue liquefies and forms a cavity; pus settles in the dependent portion while air from the bronchi enters, creating a distinct air-fluid interface. On chest X-ray or CT, this appears as a thick-walled cavity with a dependent fluid level.

This distinguishes it from simple consolidation, which is just homogeneous opacity without a cavity or fluid level. It also differs from diffuse interstitial edema, which shows interstitial markings and edema rather than a defined cavity. And it’s not a large pleural effusion, which collects in the pleural space with a meniscus rather than as a parenchymal cavity.