Penetrating abdominopelvic trauma

Penetrating abdominopelvic trauma usually occurs in the setting of gunshot and stab injuries and is associated with high morbidity and mortality. CT is the modality of choice in imaging if the patient is stable enough before surgery. The most common injuries include small bowel, large bowel, liver, spleen and intra-abdominal vasculature¹.

Pathology

Mechanisms of injury include ^1,2:

• primary penetrating foreign body:

  • stabbing

  • impalement

  • bullet

  • explosive material/shrapnel

• secondary:

  • bullet fragment

  • bone fragment

The penetrating foreign body either remains within the tissue or passes through it. When it exits the body, it can be termed a perforating injury, with an associated entry and exit wound. These are sometimes marked with a radiodense material to help trace the trajectory ¹.

In the case of projectiles, the extent of tissue damage depends on the kinetic energy of the foreign body and the type of tissue encountered. High kinetic energy projectiles often form a cavity as a result of forceful soft tissue damage upon initial penetration. Secondary cavitation can occur whereby a temporary cavity is formed by the initial force displacing tissues that then return back into place. This may result in transmission of force and damage to structures distant to the foreign body tract. Projectiles may ricochet, fragment or cause bony fragments that also cause diffuse damage. Tracts may also image differently to initial path due to patient position (arms above head for CT) and respiration ². 

Giving due consideration for widespread injury, it is important to trace the path of the foreign body/projectile. This should begin from subcutaneous fat to termination of the foreign body tract ². Useful features include:

• fat stranding

• subcutaneous gas

• retained projectile fragments

• beveling of bone

  • inward for entry

  • outward for exit

Location

The likely organ(s) involved largely depend on force and projectile path. Common injuries include ^1,2:

• hollow viscera:

  • small and large bowel, including anorectum

  • bladder

• solid viscera:

  • spleen

  • liver

  • pancreas

  • kidney

• mesentery

• intra-abdominal vasculature

• diaphragm

Less common structures injured include the gallbladder, stomach, adrenal glands, ureter and spine.

Radiographic features

Ultrasound

US can be useful to screen for abdominopelvic free fluid in an unstable patient, performed as part of the FAST scan ³. A FAST scan is not used to diagnosis or exclude solid or hollow visceral injury.

Plain Radiograph

X-rays views lack specificity and sensitivity for significant abdominopelvic injuries and can be limited by restricted views in the context of trauma i.e. supine. There is no indication for X-rays following penetrating injury to the abdomen or pelvis if CT is available immediately.

X-rays can be useful for detecting ³:

• pneumoperitoneum

  • suggestive of peritoneal violation

  • suggestive of, though not specific for, hollow viscus injury

• foreign body

  • location and number of foreign body(s)

• pneumothorax or hemothorax

  • suggestive of chest involvement or diaphragm rupture/injury

• large amount of pelvic free fluid

• rib fractures

• thoracolumbar fractures

• pelvic fractures

CT

Contrast enhanced CT is the modality of choice for evaluating injuries in penetrating abdominopelvic trauma. Some institutions have made use of enteric contrast, however this may delay management and has become unnecessary in the setting of improved resolution of CT ². There is evidence for the use of CT tractography, injection of contrast through entry wound, in detecting peritoneal violation for stab wounds ⁴.

CT is more sensitive for detecting indirect signs of intra-peritoneal violation and organ injury including ²:

• free fluid

  • hemoperitoneum

  • retroperitoneal hemorrhage

  • found in dependent positions: pouch of Douglas, Morison's pouch, paracolic gutters

  • caution should be made in interpreting hypoattenuating free fluid as this can be due to aggressive resuscitation

• pneumoperitoneum

  • not specific for visceral injury as air can enter through wound tract

• pneumothorax/hemothorax

Any foreign body tract that is adjacent to an organ should raise suspicion for injury, as temporary cavitations and shock wave forces can cause proximity damage e.g. contusion or serosal damage to bowel. Organ adjacent stranding, hematoma or pneumoperitoneum also suggest local injury.

Solid viscera organ injury is classified using the AAST scoring scale, which can help guide assessment of extent of injury. These include ²:

• splenic trauma

• hepatic trauma

• renal trauma

• pancreatic trauma:

In addition to the above CT can help screen for:

• gastrointestinal tract trauma:

  • intramural hematoma

  • discontinuity of bowel wall, focal wall thickening

  • mesenteric stranding

  • diffuse bowel wall thickening (which can occur in hypoperfusion state and/or aggressive fluid resuscitation)

  • leakage of enteric contrast

  • in anorectal injuries it is important to differentiate intra vs extra peritoneal (latter more common) ²

• mesenteric injury:

  • focal caliber change or discontinuation of mesenteric vessels

  • pseudoaneurysm

  • beading of vessels

  • active pooling of contrast (intra-mesenteric free fluid/blood takes polygonal shape as it pools within mesenteric sheets)

  • mesenteric stranding (misty mesentery sign)

• bladder trauma:

  • though relatively uncommon, bladder injuries are best assessed with a cystogram⁵

  • projectile tract near or through bladder

  • pelvic free fluid or pre-vesical hematoma

• vascular trauma ^2,6:

  • commonly involved vessels: abdominal aortic injury, SMA, iliac arteries and veins, IVC and portal vein

  • usually complete transection or partial wall defect

  • indirect signs

    • end organ hypoperfusion

    • perivascular hematoma

    • fat stranding

  • direct signs

    • active pooling/hematoma

    • focal caliber change

    • intraluminal flap

    • intramural hematoma

    • pseudoaneurysm

    • thrombosis

    • AV fistula

    • bullet embolism (suspect if bullet found remote to projectile tract)

• ureteric injury

• thoracolumbar spinal injury

• diaphragmatic rupture/injury

• hypoperfusion complex

See also

• penetrating trauma

• Penetrating thoracic trauma