36 years old male involved in shooting

Case provided by Jorge

History
36 years old male involved in shooting and presenting with abdominal gunshot wound.

Imaging findings
CT image A shows little gas and hemorrhage in the subcutaneous tissue at bullet entry site (left anterior abdominal wall) and bullet exit site (left posterior abdominal wall). There is a small amount of extraluminal gas and hemorrhage intraperitoneally next to small intestine and retroperitoneally next to descending colon as well (image B). The linear trajectory between bullet entry site und bullet exit site does not pass the intraabdominal space. Thus, there must have occurred deflection of the projectile in the body.

Diagnosis
Abdominal gunshot injury with perforation of small intestine and descending colon.

Discussion
The nature and severity of gunshot injuries depend on type of weapon, type of projectile, distance between weapon and victim, and local tissue factors. The longer the barrel of a weapon, the faster it will be when it leaves the gun. High-velocity bullets have higher kinetic energy than low-velocity bullets and have greater wounding potential. Wounding potential depends also on bullet construction in regards of deformability, fragmentation and intracorporal directional stability. Bullets deformed on impact decelerate faster, deliver more of their energy to a smaller volume of tissue and, thus, increase tissue damage.

Gunshot injuries are most severe in solid organs such as liver or brain, where damage may be caused by temporary cavitation remote from the actual bullet track. Dense tissues (bone) and loose tissues (fat) are more resistant to bullet injury. Bone can significantly alter the behavior of the projectile and its wounding capacity by slowing it down and changing its path. Particularly handgun bullets do not always follow a straight path in the body. They may bounce off of body structures or may follow fascial or tissue planes. Bullets that are deflected by anatomic structures or that follow tissue planes, tend to be traveling at lower velocity.

The objectives of imaging in gunshot injuries are to assess which tissues are injured, to estimate severity of organ damage, and to determine the path of the projectile. Accurate assessment of the bullet path and its direction of travel makes planning of surgical management more efficient.

When interpreting CT scans in gunshot injuries it is important to identify the wound track, which can be done by analyzing presence and distribution of gas and hemorrhage and assessing the localization of the projectile. If a projectile is not identified on imaging, a search must be made for a bullet exit point or a intracorporal bullet localization be outside the field of view (may need further imaging). An assessment of internal injuries including involvement of critical structures, active hemorrhage, etc. must be done. The possibility of embellished bullet fragments should be considered.

Teaching points

  • The severity of gunshot injuries depends on bullet velocity, bullet deformability, and local tissue factors.
  • Bullet injury is more severe in solid organs such as liver and brain due to temporary cavitation remote from the bullet path.
  • Assessment of the bullet path is the backbone of evaluating potential tissue damage and severity of injury.

Recommended reading

Mann et al.
Gunshot injuries: What does a radiologist need to know?
RadioGraphics. 1999; 19(5):1319–22.
http://pubs.rsna.org/doi/10.1148/radiographics.19.5.g99se331319

Hollerman et al.
Gunshot wounds: 2. Radiology.
American Journal of Roentgenology. 1990;155(4):691–702.
http://www.ajronline.org/doi/10.2214/ajr.155.4.2119096

Brogdon, Vogel, McDowell.
A Radiologic Atlas of Abuse, Torture, Terrorism, and Inflicted Trauma
CRC Press 2003
http://dx.doi.org/10.1201/9780203010853

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