What radiographic sign is commonly associated with aortic dissection?

The widened mediastinum is a significant radiographic sign often associated with aortic dissection. This condition occurs when there is a tear in the inner layer of the aorta, leading to blood collecting between the layers of the aortic wall. On a chest X-ray, this can manifest as an increase in the mediastinal width, which reflects the presence of fluid or hematoma within the mediastinal space. Recognizing this sign is critical for prompt diagnosis and intervention, as aortic dissection can be life-threatening and requires immediate medical attention.

The other options, while they may appear on radiographic images due to various conditions, do not specifically indicate aortic dissection. For instance, a bulging diaphragm is typically associated with other processes, such as diaphragmatic hernia or elevated intrathoracic pressure. An increased cardiac silhouette suggests cardiomegaly, which is not specific to aortic dissection, whereas air under the diaphragm usually indicates perforation of a hollow viscera, not relating to the aorta. Understanding the significance of the widened mediastinum is crucial for differential diagnosis in emergency and critical care settings.