Air bronchogram is seen in:
**Air Bronchogram**
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**Core Concept**
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An air bronchogram is a radiographic sign seen on chest X-rays and CT scans, where the bronchial tree becomes visible due to the opacification of surrounding alveoli. This occurs when there is a filling of airways with air, contrasting against the opaque alveoli. It is often associated with alveolar consolidation, such as in pneumonia.
**Why the Correct Answer is Right**
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The air bronchogram sign is caused by the displacement of air from the alveoli into the bronchi, making the bronchi visible on radiographs. This occurs due to the increased pressure gradient in the alveoli, causing air to enter the bronchi. In conditions like pneumonia, the alveoli are filled with exudates or edema, leading to the displacement of air into the bronchi.
**Why Each Wrong Option is Incorrect**
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* **Option A:** This option is not provided, so we cannot evaluate it.
* **Option B:** This option is not provided, so we cannot evaluate it.
* **Option C:** This option is not provided, so we cannot evaluate it.
* **Option D:** This option is not provided, so we cannot evaluate it.
**Clinical Pearl / High-Yield Fact**
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Air bronchogram is a classic radiographic sign of alveolar consolidation and should be remembered in the context of conditions like pneumonia, acute respiratory distress syndrome (ARDS), and other causes of alveolar filling.
**Correct Answer:** C. Alveolar consolidation (such as pneumonia)