A contusion differs from an abrasion in that it characteristically involves which of the following?

Question

Accepted Answer

D. Rupture of blood vessels in the dermis and subcutaneous tissue with intact overlying skin. ## Contusion: Mechanism and Pathophysiology

### Definition and Core Feature

**Key Point:** A contusion (bruise) is a blunt force injury characterized by rupture of blood vessels with hemorrhage into surrounding tissues, while the overlying skin remains intact.

### Pathophysiology of Contusion

**High-Yield:** The hallmark of a contusion is **intact skin overlying hemorrhage**. This distinguishes it from lacerations (which breach skin) and abrasions (which remove epidermis).

### Mechanism

1. Blunt force applied to skin and underlying tissues
2. Compressive and shearing forces rupture capillaries and small vessels
3. Blood extravasates into dermis and subcutaneous tissue
4. Overlying epidermis remains unbroken
5. Visible discoloration (ecchymosis) develops as hemoglobin is metabolized

### Color Changes Over Time (Forensic Dating)

| Timeline | Color | Mechanism |
|----------|-------|----------|
| **0–2 days** | Red, blue, purple | Oxyhemoglobin, deoxyhemoglobin |
| **3–5 days** | Green | Biliverdin formation |
| **5–7 days** | Yellow-brown | Bilirubin formation |
| **7–10 days** | Brown, fading | Hemosiderin |
| **>2 weeks** | Resolved | Complete reabsorption |

**Clinical Pearl:** Contusions are common in assault cases and accidental trauma. Multiple contusions in different stages of healing suggest repeated trauma over time — a red flag for abuse.

### Distinction from Other Injuries

| Injury | Skin Integrity | Bleeding | Depth |
|--------|---|---|---|
| **Contusion** | Intact | Subcutaneous hemorrhage | Dermis + subcutaneous |
| **Abrasion** | Disrupted (removed) | Minimal capillary ooze | Epidermis + superficial dermis |
| **Laceration** | Disrupted (torn) | Profuse | Full thickness |

**Mnemonic:** **C**ontusion = **C**losed (skin intact), **C**ollection of blood underneath.

Answer

A. Superficial scraping of the skin surface without any subcutaneous involvement

Answer

B. Disruption of the epidermis with visible dirt particles embedded in the wound

Answer

C. Full-thickness laceration of skin with irregular wound margins

A contusion differs from an abrasion in that it characteristically involves which of the following?

Explanation

Contusion: Mechanism and Pathophysiology

Definition and Core Feature

Pathophysiology of Contusion

Mechanism

Color Changes Over Time (Forensic Dating)

Distinction from Other Injuries

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Timeline	Color	Mechanism
0–2 days	Red, blue, purple	Oxyhemoglobin, deoxyhemoglobin
3–5 days	Green	Biliverdin formation
5–7 days	Yellow-brown	Bilirubin formation
7–10 days	Brown, fading	Hemosiderin
>2 weeks	Resolved	Complete reabsorption

Injury	Skin Integrity	Bleeding	Depth
Contusion	Intact	Subcutaneous hemorrhage	Dermis + subcutaneous
Abrasion	Disrupted (removed)	Minimal capillary ooze	Epidermis + superficial dermis
Laceration	Disrupted (torn)	Profuse	Full thickness