How does a pulmonary embolus typically appear on a chest X-ray?

A pulmonary embolus often manifests as a peripheral wedge-shaped infiltrate on a chest X-ray due to the way it obstructs blood flow in the lungs. This type of infiltrate is commonly referred to as a "hampton's hump". The wedge shape occurs because the area of lung affected by the embolism is supplied by a blocked pulmonary artery, potentially causing infarction and localized edema.

In the case of a pulmonary embolism, this wedge-shaped appearance signifies that the distal lung region becomes hypoperfused, leading to the distinctive radiographic finding that aids in diagnosis. While other patterns exist on chest X-rays that may indicate various conditions, the peripheral wedge-shaped infiltrate is specifically associated with pulmonary emboli, marking its importance in clinical radiographic assessment.

The increased density from consolidation typically indicates diseases like pneumonia, while a ground glass appearance is more seen in conditions such as pulmonary edema or interstitial lung disease. A reticulonodular pattern may be seen in fibrotic lung diseases, but these appearances do not specifically indicate a pulmonary embolism. This distinction underscores why recognizing the characteristic peripheral wedge-shaped infiltrate is crucial in the evaluation of a suspected pulmonary embolism.