Right hemithorax with right side shift of mediastinum is due to –
**Core Concept**
The question is testing the understanding of **mediastinal shift** in relation to **thoracic cavity** conditions, specifically focusing on the effects of **volume increase** or **decrease** within the thorax on mediastinal positioning.
**Why the Correct Answer is Right**
A right hemithorax with a right side shift of mediastinum typically indicates a condition that increases volume or pressure within the right thoracic cavity, pushing the mediastinum to the right. This could be due to a **large pleural effusion**, **pneumothorax**, or other space-occupying lesions.
**Why Each Wrong Option is Incorrect**
**Option A:** Would typically cause a left shift of the mediastinum if it's a condition affecting the left side.
**Option B:** Conditions causing atelectasis would result in a shift of the mediastinum towards the affected side due to decreased volume.
**Clinical Pearl / High-Yield Fact**
Remember, the mediastinum shifts away from a condition that increases the volume of a hemithorax (like pneumothorax or large pleural effusion) and towards a condition that decreases the volume (like atelectasis).
**Correct Answer:** D. Right sided massive pleural effusion or tension pneumothorax.