What does a concave superior interface or border in radiology usually indicate?

A concave superior interface or border seen in radiology typically indicates the presence of a pleural effusion. This is because, in cases of pleural effusion, fluid accumulates in the pleural space, which can create a characteristic appearance on imaging studies. The concave line refers to the fluid level that forms at the interface of the pleural fluid and the air in the lung, marking the upper border of the effusion.

In the context of other conditions:

• Pneumonia generally presents with consolidation, which is more likely to show an irregular or ill-defined border rather than a distinct concave shape.

• A pulmonary embolus typically does not create a visible concave border; it might lead to complications such as atelectasis or infarction but is not characterized by a concave superior border.

• Tuberculosis can result in various findings on imaging, such as cavitary lesions or infiltrates, but would not specifically produce a concave superior interface.

Thus, the presence of a concave superior interface on a radiological image is most consistently linked to pleural effusion.