**Question:** Kerley B lines seen in:

A. Pleural Effusion
B. Pulmonary Edema
C. Pleural Effusion and Pulmonary Edema
D. None of the above

**Core Concept:** Kerley B lines are a specific radiological feature seen in certain medical conditions involving the lungs and pleura. These lines represent the interlobular septa within the lungs that are partially effaced due to increased interstitial fluid or air-fluid levels.

**Why the Correct Answer is Right:**

Correct Answer: C (Pleural Effusion and Pulmonary Edema)

Kerley B lines are primarily associated with two conditions:
1. **Pleural Effusion:** Effusion is the accumulation of fluid between the two pleural layers, causing the partial effacement of interlobular septa. This leads to the appearance of Kerley B lines.
2. **Pulmonary Edema:** Pulmonary edema is an accumulation of fluid in the pulmonary interstitium, the space between the alveoli and the pleura. This edema causes the interlobular septa to be partially effaced, resulting in the presence of Kerley B lines.

**Why Each Wrong Option is Incorrect:**

A. Pleural Effusion is a separate condition from pulmonary edema, which is characterized by fluid in the interstitium and alveoli. Kerley B lines are indicative of pleural effusion, not pulmonary edema alone.

B. Pulmonary Edema is a distinct condition, but Kerley B lines are seen in both pleural effusion and pulmonary edema, not just pulmonary edema.

C. Both pleural effusion and pulmonary edema can lead to the presence of Kerley B lines. The correct answer is a combination of both conditions.

D. None of the above: While the correct answer is a combination of pleural effusion and pulmonary edema, the other conditions are not correct because they do not involve the effacement of interlobular septa, which is the key feature of Kerley B lines.

**Clinical Pearl:**

Kerley B lines are a useful radiological finding in diagnosing pleural effusion and pulmonary edema, which are common causes of respiratory distress. A thorough clinical examination, history-taking, and chest X-ray are essential in making a proper diagnosis in such cases.