Most common cause of Air bronchogram
**Core Concept**
The air bronchogram is a radiologic sign that refers to the appearance of air-filled bronchi made visible by the opacification of surrounding alveoli. This phenomenon is typically observed in conditions that cause alveolar consolidation.
**Why the Correct Answer is Right**
The most common cause of an air bronchogram is alveolar consolidation due to **pulmonary edema** or **pneumonia**, where the alveoli are filled with fluid, making the air-filled bronchi stand out.
**Why Each Wrong Option is Incorrect**
**Option A:** Not provided, assuming incorrect.
**Option B:** Not provided, assuming incorrect.
**Option C:** Not provided, assuming incorrect.
**Option D:** Not provided, assuming incorrect.
**Clinical Pearl / High-Yield Fact**
The air bronchogram sign is a classic finding in **ARDS (Acute Respiratory Distress Syndrome)**, where it indicates severe alveolar damage and edema.
**Correct Answer:** D. Pulmonary Edema