What finding on an X-ray is characteristic of pleural effusion?

A pleural effusion occurs when excess fluid accumulates in the pleural space surrounding the lungs, and specific radiographic findings can help identify this condition on an X-ray. The characteristic finding of pleural effusion is the blunting or shunting of the costophrenic angles. This happens because the fluid collects in the pleural cavity, leading to a dulling of the sharp angle where the diaphragm meets the rib cage.

As the fluid fills the pleural space, the costophrenic angles, which are normally sharp and defined, appear rounded or obscured on the X-ray. This indicates a significant accumulation of fluid, and clinicians often use this finding as a pointer for further evaluation or intervention, such as thoracentesis.

Enlarged heart silhouette, increased lung markings, and pneumothorax are not characteristic findings of pleural effusion. An enlarged heart silhouette typically indicates cardiomegaly rather than fluid accumulation. Increased lung markings can suggest conditions such as pulmonary edema or interstitial lung disease, while pneumothorax presents differently and would show a visceral pleural line with associated chest wall changes. Thus, the appearance of blunting or shunting of the costophrenic angle is a definitive finding suggest