Decubitus positioning in thoracic imaging helps identify layering of pleural fluid due to gravity by which finding?

• A. Fluid layers away from the dependent chest wall.
• B. Fluid layers along the dependent chest wall.
• C. No layering occurs with decubitus views.
• D. Decubitus views are only for bone assessment.

Answer: (B)

When a thoracic image is taken in decubitus position, gravity pulls pleural fluid toward the lowest, dependent side. The fluid then layers along the dependent chest wall, creating a distinct horizontal fluid level that follows the side lying on the table. This layering makes even small effusions visible on decubitus views because the fluid pools against the dependent border.

So the best description is that the fluid layers along the dependent chest wall. It would not layer away from the dependent side, and layering does occur in decubitus views—these views are specifically useful for detecting pleural fluid and distinguishing it from air, not solely for bone assessment.