Blunt Abdominal Injury

Overview

Definition

Blunt abdominal injury is defined as damage to the abdomen and/or abdominal organs secondary to impact with a blunt (not penetrating) object or surface.

Epidemiology and etiology

• Blunt abdominal injuries make up 80% of all abdominal injuries presenting to emergency departments in the United States.
• Causes:
  • Most commonly caused by a motor vehicle collision (MVC)
  • Blows to abdomen and falls are also common causes.
• Most commonly injured organs: spleen and liver

Anatomy

• Peritoneal cavity: 
  • Subdivided into intrathoracic and abdominal segments
  • Intrathoracic segment includes:
    • Diaphragm
    • Liver
    • Spleen
    • Stomach
    • Transverse colon
• Retroperitoneum: 
  • Hard to access on physical exam and peritoneal lavage
  • Contains: 
    • Aorta
    • Vena cava
    • Pancreas
    • Kidney
    • Ureters
    • Portions of the duodenum and colon
• Pelvic compartment: contains pelvic organs (bladder, uterus/ovaries, or prostate)

Pathophysiology

Blunt abdominal trauma can occur due to several pathologic processes:

• Deceleration:
  • Shear forces cause organs and vasculature to tear from their points of attachment to the peritoneum.
  • Kidneys are the most vulnerable.
• Crushing:
  • Anterior forces trap organs between the anterior abdominal wall and the posterior thoracic cage.
  • Solid organs are sensitive to the crushing mechanism of injury.
• External compression:
  • A direct blow or external compression against a rigid fixed structure
  • Hollow organs are more vulnerable due to sudden ↑ in intra-abdominal pressure

Diagnosis

Because of the wide variety and severity of injuries associated with blunt abdominal trauma, a prompt but careful history and physical exam are necessary to direct investigation with imaging studies.

History

• Mechanism of trauma: 
  • May suggest severity of injury
  • MVC:
    • Position seated in the car
    • Other fatalities in the car
    • Amount of intrusion into the car (> 6 inches predicts serious injury)
• History of previous trauma
• Drug (illicit and prescription) or alcohol use by the patient 
• Last thing the patient had to eat or drink: important for intubation/anesthesia consideration
• Prior surgical history

Physical exam

• Airway, breathing, circulation (ABC) assessment:
  • Airway:
    • Look for foreign objects blocking airway (loose teeth are common foreign bodies in high-force trauma).
    • Assess for injury to the trachea (tracheal injury means intubation will be complex).
    • Listen for unusual breathing sounds (stridor suggests narrowing by a foreign body or edema).
  • Breathing:
    • Look at chest wall movement for even and spontaneous breathing (uneven chest movement suggests “flail chest”).
    • Listen to breath sounds (muffled or uneven may suggest pneumothorax or hemothorax).
  • Circulation:
    • Palpate pulses on all 4 extremities (tachycardia suggests hemodynamic instability or pneumothorax).
    • Assess capillary refill on extremities.
• Secondary survey: 
  • Examine patient head to toe.
  • Base imaging decision on exam findings.
  • External injury should prompt investigation for corresponding internal injury.
  • If the patient is alert and free from distracting pain, the most specific symptoms of blunt abdominal trauma are:
    • Abdominal pain
    • Abdominal tenderness
    • Peritoneal findings
  • Signs concerning for severe intra-abdominal injury:
    • Seat belt sign
    • Hypotension
    • Rebound tenderness
    • Abdominal distention
    • Abdominal guarding
    • Concomitant femur fracture

Imaging studies

• FAST (focused assessment with sonography for trauma): used in all patients (stable or unstable) to look for intraperitoneal blood and pericardial effusion: 
  • Hemodynamically unstable patients:
    • Positive FAST →  emergent laparotomy
    • Negative FAST → search for extra-abdominal bleeding sources (femur fracture)
    • Equivocal FAST → diagnostic peritoneal lavage (DPL) or stabilize patient and computed tomography (CT) scan
  • Hemodynamically stable patients: 
    • Positive FAST → emergent laparotomy
    • Negative FAST, low risk for intra-abdominal injury → observation
    • Negative or equivocal FAST with high risk for intra-abdominal injury → CT scan
• X-ray: directed by exam findings:
  • Chest X-ray: can show free intraperitoneal air, herniation of abdominal contents
  • Pelvic X-ray: Pelvic bone fractures can be a source of bleeding or bladder injury.
• CT scan abdomen with contrast:
  • Imaging of choice for stable patients 
  • Provides information regarding retroperitoneal structures, diaphragm, and solid abdominal organs

Other diagnostic studies

• Hematocrit: 
  • < 30% suggestive of intra-abdominal injury 
  • Normal hematocrit does not rule out severe injury.
• Urinalysis: Blood is suggestive of serious renal injury.
• Liver function tests
• DPL:
  • Invasive procedure used to evaluate the presence of blood in the abdominal cavity: A catheter is put into the peritoneal cavity and fluid is aspirated and evaluated.
  • Not often used: alternative when CT scan and FAST are not available

Features of abdominal injuries by organ

Management

Careful investigation will yield evidence of injured organs, directing further management.

Clinical Relevance

• Penetrating abdominal injury: typically involves the violation of the abdominal cavity by a gunshot wound or stab wound. Most commonly injured structures are small bowels, followed by the colon, liver, and vascular structures. Treatment is exploratory laparotomy.
• Splenic injury: In blunt injuries, the liver and spleen are the most commonly injured organs. Usually, splenic injury is associated with lower-left rib fractures. Features of splenic injury include hypotension, tachycardia, abdominal pain, left chest wall pain, and left shoulder pain (referred pain due to phrenic nerve irritation from splenic hemorrhage).
• Pelvic injury: Pelvic injuries and pelvic fractures are among the worst complications of blunt abdominal injuries. Clinical features include hypotension, pain with movement, gross hematuria, and peri-pelvic ecchymoses. A digital rectal examination is important to identify injury to the rectum and locate the prostate. Treatment is usually limited to supportive care, but surgical stabilization may sometimes be necessary.
• ABC assessment: The ABC assessment is an approach to managing critically ill patients. Airway, breathing, and circulation is the essential 1st step to perform when encountering a patient. The steps are easily adaptive to many situations, including unresponsive patients, cardiac arrests, and critical medical or trauma patients. For trauma patients, ABC includes the primary survey, the initial evaluation, and management of injuries.