**Question:** All the following are radiological features of Chronic Cor pulmonale except:

A. Pulmonary vasculature dilatation (pulmonary arterial dilatation)
B. Increased pulmonary vascular markings
C. Atelectasis
D. Pleural effusion

**Core Concept:** Chronic Cor pulmonale is a type of right heart failure caused by chronic obstructive pulmonary disease (COPD), bronchiectasis, pulmonary fibrosis, or other chronic lung diseases. The radiological features of Chronic Cor pulmonale include pulmonary arterial dilatation, increased pulmonary vascular markings, and pulmonary vascular congestion.

**Why the Correct Answer is Right:**

1. **Atelectasis (Diffuse interstitial infiltrate):** Atelectasis refers to the collapse of alveoli, leading to a diffuse interstitial infiltrate on radiographs. This is a feature of acute respiratory distress syndrome (ARDS) and not Chronic Cor pulmonale.

2. **Diffuse interstitial infiltrate (Atelectasis):** Similar to option A, a diffuse interstitial infiltrate is a common feature of acute respiratory distress syndrome (ARDS) rather than Chronic Cor pulmonale.

3. **Pleural effusion (A):** Pleural effusion occurs due to increased hydrostatic pressure in the pulmonary capillaries and interstitium, which leads to fluid leakage into the pleural cavity. This is a feature of congestive heart failure (CHF) and not Chronic Cor pulmonale.

**Why Each Wrong Option is Incorrect:**

1. **Pulmonary vasculature dilatation (A):** Pulmonary arterial dilatation is a key feature of Chronic Cor pulmonale, occurring due to increased pulmonary arterial pressure and volume load on the right ventricle.
2. **Increased pulmonary vascular markings (B):** Increased pulmonary vascular markings are seen on chest X-ray due to increased pulmonary vascular congestion in Chronic Cor pulmonale.
3. **Pleural effusion (D):** Pleural effusion is a feature of congestive heart failure (CHF) and not Chronic Cor pulmonale.

**Clinical Pearl:** Chronic Cor pulmonale is a common complication of chronic lung diseases such as COPD, bronchiectasis, and pulmonary fibrosis. The radiological features include pulmonary arterial dilatation, increased pulmonary vascular markings, and pulmonary vascular congestion. Atelectasis, diffuse interstitial infiltrate, and pleural effusion are more commonly seen in congestive heart failure (CHF) rather than Chronic Cor pulmonale.