A 32-year-old man is brought to the emergency department following a gunshot wound to the left chest. On examination, he has a single entry wound over the left anterior axillary line at the 5th intercostal space with minimal external bleeding. The exit wound is noted over the left posterior axillary line at the same level, with beveling of the skin edges. Chest X-ray shows a pneumothorax and pulmonary contusion. Which of the following features of the exit wound is most characteristic and helps differentiate it from the entry wound?

Explanation

## Exit Wound Characteristics **Key Point:** Exit wounds are typically larger than entry wounds and have everted (turned outward) margins without soot deposition, as the bullet exits from inside the body. ### Distinguishing Features of Exit vs Entry Wounds | Feature | Entry Wound | Exit Wound | |---------|-------------|------------| | **Diameter** | Smaller (usually matches bullet caliber) | Larger (due to tissue destruction and temporary cavity) | | **Margins** | Inverted (inrolled inward) | Everted (rolled outward) | | **Soot/Fouling** | Present (soot from bullet surface) | Absent (no soot deposition) | | **Abrasion collar** | Present (tissue abraded by bullet) | Absent or minimal | | **Bleeding** | Minimal external bleeding | Profuse external bleeding | | **Shape** | Regular, round/oval | Irregular, stellate (if high velocity) | **High-Yield:** The presence of an abrasion collar is pathognomonic for an entry wound. Exit wounds never have an abrasion collar because the bullet is exiting, not entering. **Clinical Pearl:** In this case, the beveled skin edges at the exit wound represent tissue destruction from the temporary cavity created by the bullet's passage through the chest, resulting in the characteristic everted appearance. ### Mechanism of Exit Wound Formation 1. Bullet penetrates skin from outside → creates entry wound with inverted margins 2. Temporary cavity expands within tissues → maximum at exit point 3. Bullet exits, pushing tissue outward → everted margins 4. No soot reaches exit because bullet surface has already deposited fouling at entry **Warning:** Do not confuse exit wounds with entry wounds based on size alone—some high-velocity entry wounds can be large. The combination of everted margins + absence of soot + larger diameter is diagnostic for exit wounds.