**Question:** All are chest x-ray signs of pulmonary embolism except

A. Kerley B lines
B. Pleural effusion
C. Consolidation
D. Bronchial markings

**Correct Answer:** D. Bronchial markings

**Core Concept:**
Pulmonary embolism (PE) is a potentially life-threatening condition caused by the blockage of a pulmonary artery by a blood clot. Chest x-ray is a common initial imaging modality used to diagnose PE and detect its associated signs. Key findings on chest x-ray include:

1. Kerley B lines: Unilateral or bilateral, horizontal, symmetrical, and regular pleural lines, which represent increased interstitial fluid and edema.
2. Pleural effusion: An accumulation of fluid between the pleural layers, resulting in an increase in the distance between the pleural surfaces.
3. Consolidation: A region of decreased lung opacity due to alveolar filling by fluid, pus, or hemorrhage.

**Why the Correct Answer is Right:**
Bronchial markings are prominent and well-defined round structures that represent the outline of the bronchi on a chest x-ray. They are normal findings on a chest x-ray and do not represent any pathological processes like those seen in pulmonary embolism.

**Why Each Wrong Option is Incorrect:**
A. Kerley B lines are abnormal pleural lines seen on chest x-ray due to increased interstitial fluid and edema in conditions such as pneumonia, congestive heart failure, or pulmonary edema. They are a characteristic finding in pulmonary embolism and do not represent a negative sign for PE.
B. Pleural effusion is an accumulation of fluid between the pleural layers, which can be seen on chest x-ray as a decrease in the distance between pleural surfaces and an increase in opacity. Pleural effusion is a potential complication of pulmonary embolism, and its absence does not rule out the diagnosis.
C. Consolidation refers to a region of decreased lung opacity due to alveolar filling, which can be caused by various factors such as hemorrhage, infection, or fibrosis. It is not specific to pulmonary embolism and can be seen in other conditions like pneumonia or lung infarction.

**Clinical Pearl:**
It is essential for medical students and physicians to be familiar with normal radiological findings on a chest x-ray to correctly interpret abnormal findings and make an accurate diagnosis. A thorough understanding of normal chest x-ray findings is vital for differentiating between normal and abnormal findings and making an accurate diagnosis.