Prevalence: 200,000 gun-related injuries per year; 31,224 firearm-related deaths in USA (2007)

Firearms: handgun, rifle (great energy), shotgun

Projectiles:

1. bullet:
   • jacketed bullet with mantle of copper
   • semi jacketed bullet = exposed lead at tip
   • non jacketed bullet
2. pellets of steel / lead:
   • birdshot = small pellets
   • buckshot =large pellets

Assessment of type of projectile:

• fully jacketed bullets show no trail of lead fragments
• semi- / non jacketed bullets distribute lead fragments along bullet track
• hollow-point bullets transform into mushroom shape
• “lead snowstorm” of high-velocity soft-point rifle bullets:
  • conical distribution with apex pointing toward entry site
• steel pellets remain round, lead pellets become deformed + fragmented

Assessment of trajectory:

• bullet tips points to entry wound (after tumbling through 180°):
  • impact deformation of bullet modifies tumbling
  • bullet + bone fragments deposited along track
  • bone fracture beveled toward the direction of travel

Location: liver >small bowel >colon >spleen >kidney >pancreas

Pathophysiology of gunshot: complex interaction of mass, velocity, path, type of organ

1. projectile: bullet imparts kinetic energy to surrounding tissue → tissue displacement radially away from path of bullet → temporary cavity much larger than bullet diameter (depending on mass, material, design, velocity of projectile)
2. tissue: damage depends on specific gravity (density) and elasticity of type of soft tissue ↓ density + ↑ elasticity: skin, lung (less damage) ↑ density + ↓ elasticity: liver, spleen, muscle
3. fluid: pressure wave → bursting of fluid-filled organ
4. bone: bone fragments = numerous secondary missiles

Cx: pellet embolization, magnetization in MRI