Continuous diaphragm sign | Radiology Signs

Answer:

Air accumulation in the mediastinum (pneumomediastinum), pericardium (pneumopericardium), or peritoneal cavity (pneumoperitoneum) outlines the central diaphragm, making it continuously visible across the midline on an chest X-ray. Pneumomediastinum commonly arises from alveolar rupture (e.g., asthma exacerbation, mechanical ventilation), airway rupture, esophageal perforation (e.g., Boerhaave syndrome), or trauma; pneumoperitoneum from gastrointestinal perforation or postsurgical air; pneumopericardium from trauma, iatrogenic causes, or spontaneous rupture.

Why is it called so?

The sign is named for the continuous visualization of the entire diaphragm contour from right to left hemidiaphragm as a single uninterrupted line, unlike the normal appearance where the central portion is obscured by the heart and mediastinum. When air (radiolucent) interposes between these structures and the superior diaphragm, the central outline becomes visible on a chest radiograph, producing the Continuous diaphragm sign.

Pathophysiology

Normally, the central diaphragm is silhouetted by the adjacent heart and mediastinum due to similar radiographic densities, obscuring it on an chest X-ray and leaving only the peripheral hemidiaphragms visible against lucent lung. Free air in the mediastinum, pericardium, or subdiaphragmatic peritoneum interposes between the heart base and diaphragm superior surface, creating a lucent interface that outlines the central diaphragm due to density contrast with overlying soft tissues.

Alternative names: Continuous left hemidiaphragm sign (specific to lateral view or left-sided emphasis)

Other associated named signs: Naclerio’s V sign, Ring-around-artery sign (in pneumomediastinum)