## Visceral Pleural Line in Pneumothorax ### Definition and Appearance The visceral pleural line (also called the lung edge or pleural stripe) is the most direct and classic radiological sign of pneumothorax. **Key Point:** The visceral pleural line appears as a **thin, white, curvilinear opacity** that parallels the chest wall, with **lucency (darkness) medial to it** representing the pneumothorax space. ### Radiographic Characteristics | Feature | Detail | |---------|--------| | **Appearance** | Thin white line | | **Shape** | Curved, paralleling thoracic wall | | **Location** | Separates collapsed lung from chest wall | | **Medial to line** | Lucent (air-filled pleural space) | | **Lateral to line** | Normal chest wall and ribs | | **Thickness** | 1–2 mm | ### Pathophysiology 1. Air enters pleural space → visceral pleura is pushed inward 2. Lung collapses toward hilum 3. Pleural interface becomes visible on X-ray (normally invisible) 4. The collapsed lung tissue appears white; the pneumothorax space appears black (lucent) ### Clinical Significance - **Gold standard sign** for pneumothorax diagnosis on frontal CXR - Best seen on **erect, expiratory films** (increases contrast between lung and air) - May be absent or subtle in small pneumothoraces or supine patients - Should be sought systematically from apex to base **Mnemonic:** **PLEURAL LINE** = **P**erfect **L**ucency **E**dge **U**nder **R**ibs **A**nd **L**ungs **L**ine **I**ndicates **N**ew **E**ntry of air **High-Yield:** Expiratory films increase the visibility of the visceral pleural line by reducing lung volume and increasing the relative lucency of the pneumothorax. 
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