Abdominal Trauma, Imaging

Basics

Description

In unstable trauma patients, prompt US can be used to determine the need for emergent laparotomy. In stable trauma patients in whom intra-abdominal injury is suspected, CT, with IV contrast only, is the diagnostic test of choice

Diagnosis

Signs and Symptoms

  • Abdominal trauma can be seen in a variety of patients ranging from those with isolated abdominal injury to multisystem trauma
  • Abdominal trauma is divided into blunt and penetrating injuries. Penetrating abdominal injuries can further be divided into stab wounds and gunshot wounds
  • Hemodynamic status should be the primary initial focus of evaluation. Most unstable patients will require early surgical management, while many stable patients with abdominal trauma may be managed nonoperatively

History
  • History should include mechanism of injury, restraint use and type, airbag or helmet use, prehospital vital signs, initial mental status, and change in mental status
  • AMPLE history (allergies-to-medications and radiographic contrast agents, medications taken, past medical and surgical history, last meal, events leading up to the injury)

Physical Exam
  • A comprehensive physical exam should start with ABCDE survey and include full exposure of the patient and careful palpation of all abdominal quadrants
  • The abdominal physical exam can be inaccurate in intoxicated, uncooperative, and acutely ill patients. Serial exams increase sensitivity for occult injuries

Essential Workup

See “Abdominal Trauma, Blunt” and “Abdominal Trauma, Penetrating”

Diagnostic Tests and Interpretation

General approach to imaging in abdominal trauma:
  • Unstable trauma patients:
    • Unstable patients should have a bedside FAST performed immediately as part of the primary survey (circulation). A positive FAST suggests that intra-abdominal bleeding is the source of hypotension. A negative FAST suggests either a retroperitoneal bleed, blood loss in the field, bleeding from an unstable pelvic fracture, or hemorrhage into another body cavity
    • A surgeon should be consulted immediately to prepare for definitive operative care of the patient
  • Stable trauma patients: The 2 main diagnostic tools in hemodynamically stable abdominal trauma patients include:
    • US: Initial screening test of choice for hemodynamically stable patients. While there is some evidence it is low yield, a positive FAST in the stable trauma patient warns the clinician about the possibility of impending hemodynamic deterioration. CT scan and surgical consult should be rapidly facilitated in this group of patients
    • CT scan: The definitive test for stable abdominal trauma patients. CT scanning will diagnose solid organ and retroperitoneal injuries. CT imaging allows a determination of whether an embolization procedure is warranted for hemorrhage control. It is indicated in all stable patients with stab wounds if violation of the peritoneum is suspected. It is also indicated in patients with gross hematuria to look for renal injury

Lab
  • Blood type and screen
  • CBC
  • Electrolytes and creatinine
  • UA

Imaging
  • US: FAST exam focuses on dependent intraperitoneal areas where blood can accumulate which include: Hepatorenal space (Morison pouch), splenorenal space, suprapubic region (bladder and pouch of Douglas), pericardium
    • Advantages:
      • Rapid, noninvasive, portable
      • Good sensitivity for significant (∼500 mL) intraperitoneal free fluid
    • Disadvantages:
      • Operator dependent
      • Does not reliably identify solid organ (e.g., spleen and liver lacerations), bowel, or retroperitoneal injuries. May be negative with pelvic fractures despite significant hemorrhage
    • Limitations:
      • Obesity; subcutaneous emphysema
    • Positive test:
      • Adequate exam includes visualization of the right upper quadrant, left upper quadrant, suprapubic/pelvis, and cardiac areas
      • Sensitivity increases with serial exams
  • CT scan:
    • Advantages:
      • Sensitive and specific for hemoperitoneum, solid organ injury, retroperitoneal injury, and adjacent spinal injury
      • Guides nonoperative approach to solid organ injuries, which may be managed with observation or interventional radiology mediated embolectomy
    • Disadvantages:
      • Exposes patients to radiation and contrast
      • Diaphragmatic, mesenteric, pancreatic, and bowel injuries may be missed, especially if performed immediately after injury
    • Indications:
      • Hemodynamically stable patients when abdominal injury suspected
    • Contraindications:
      • Pre-existing indication for exploratory, laparotomy, hemodynamic instability, previous contrast reaction
    • Considerations:
      • “Pan-scans,” which include CT imaging of head, C-spine, chest, and abdomen/pelvis are controversial. While they may find occult injuries, many of these injuries may be inconsequential
      • IV contrast is sufficient in the abdominal trauma patient. Oral and rectal contrast is rarely needed
      • Angiography:
        • Unstable patients and pelvic fractures
        • This approach can embolize vessels from pelvis, spleen, etc.

Diagnostic Procedures/Other
  • Diagnostic peritoneal lavage: Largely replaced by FAST and CT, but useful in certain situations:
    • Steps:
      • First, attempt aspiration of free peritoneal blood. Recovery of >10 mL of frank blood indicates intraperitoneal injury
      • Second, if aspiration negative, lavage is conducted by introducing fluid into the peritoneum, then recovered and analyzed
    • Advantages:
      • Can quickly discern if intra-abdominal injury is the source of hypotension in severely injured patients with equivocal FAST exam
      • Occasionally helpful in detecting mesenteric and hollow organ injuries in patients in whom other diagnostic tests and serial examinations are limited
      • Relatively simple to perform with low complication rate
    • Disadvantages:
      • Invasive; 1–2% complication rate
      • Does not identify specific organ injury
      • False-negative and false-positive tests can occur from technical failure
      • Extremely sensitive for hemoperitoneum; can lead to unnecessary laparotomy if done in stable patients
    • Contraindications:
      • Absolute: Pre-existing indication for exploratory laparotomy
      • Relative: Previous abdominal surgery, severe abdominal distention, second- or third-trimester pregnancy
    • Considerations:
      • Foley catheter and nasogastric tube placement is recommended before beginning the procedure
    • Positive test:
      • Aspiration of >10 mL of blood, bile, bowel contents, or urine
      • Diagnostic peritoneal lavage fluid in the urine or chest tube
      • Blunt trauma with >100,000 erythrocytes/mm3
      • Penetrating trauma >1,000 erythrocytes/mm3
  • Local wound exploration: Can be useful to determine depth of stab wounds. This is especially true of anterior abdominal stab wounds. If the wound is superficial to the abdominal cavity, patients can be safely discharged home if otherwise appropriate. Otherwise, further diagnostic study indicated

Pediatric Considerations
The diagnostic approach to pediatric abdominal trauma is generally the same as the approach to adult abdominal trauma


Pregnancy Considerations
  • General approach:
    • The first priority in pregnant trauma patients is to stabilize the mother, as maternal demise will lead to fetal demise
    • If the EGA is >20 wk (uterus palpated above the umbilicus), place the mother in 30 degrees left lateral decubitus as it may improve perfusion
    • Proceed as one would for a nonpregnant patient: FAST for unstable patients to determine need for emergent laparotomy and CT as needed in stable patients
    • The radiation dose of essentially all imaging studies used in the initial evaluation of trauma patients falls below the threshold of doses associated with fetal anomalies
    • IV contrast is recommended as the diagnostic benefit outweighs the potential harms to the fetus
    • Because of prolonged exam times, MR is rarely used in the acute evaluation of trauma patients
    • If after initial evaluation both mother and fetus are stable, a viable fetus (>24 wk) should undergo 4 hr of continuous cardiotocographic observation to ensure no placental abruption
    • Placental abruption occurs when inelastic placenta separates from the elastic uterus during sudden deformation of the uterus. US and CT can sometimes make the diagnosis but are not sufficiently sensitive. Thus, fetal monitoring test of choice

Differential Diagnosis

See “Abdominal Trauma, Blunt” and “Abdominal Trauma, Penetrating”

Treatment

Pre Hospital

All patients with a significant mechanism of injury or suspicion of major trauma should be triaged to a designated trauma center

Initial Stabilization/Therapy

Ed Treatment/Procedures

  • See “Abdominal Trauma, Blunt” and “Abdominal Trauma, Penetrating”
  • In the setting of hemorrhagic shock without immediate access to blood products, judicious use of isotonic fluids is appropriate
  • 2 large-bore IV catheters should be placed
  • Blood transfusion is indicated for all hemodynamically unstable abdominal trauma patients. O-negative or O-positive blood can be used in men/women beyond childbearing age
  • Hemodynamically unstable trauma patients with altered mental status and inability to protect airway will usually need endotracheal intubation prior to transfer to operating suite

Ongoing Care

Disposition

Admission Criteria
  • All unstable trauma patients require admission to the hospital and most will require surgical management
  • Most multisystem trauma patients who also have abdominal trauma will need admission
  • Pregnant women >24 wk gestation should be admitted for fetal–maternal monitoring
  • Stable trauma patients are divided into 3 classes:
    • Gunshot wounds to abdomen: Almost all will require admission. Rate of surgical exploration is high in this category due to elevated risk of organ injury
    • Stab wounds to abdomen: Patients with penetration of fascia will require admission. US, CT, local wound exploration, or physical exam will define patients who need operative management
    • Blunt abdominal trauma: US, CT, or exam will define patients who need admission

Discharge Criteria
Patients with stable hemodynamics during their ED course with a negative evaluation and reliable follow-up may be considered for discharge

Follow-Up Recommendations

A small subset of discharged patients may have an undiagnosed injury (most commonly intestinal or pancreatic). Patients must be instructed to return to the ED with worsening abdominal pain, distention, vomiting, or rectal bleeding

Pearls and Pitfalls

  • In unstable trauma patients, promptly complete a FAST exam to determine the need for emergent laparotomy
  • In stable trauma patients, CT is the test of choice to detect injury and guide treatment
  • In patients with a negative CT, consider the possibility of diaphragmatic, bowel, pancreatic, and mesenteric injury
  • Consider serial US exams. This is especially important if there is a change in the patient's hemodynamic status or physical exam
  • Many stable adult and pediatric trauma patients are now being managed nonoperatively based on CT findings
  • “Pan CT scan” decreases missed injury rate but exposes patients to radiation, contrast, and increased downstream testing
  • Pitfalls include:
    • Not recognizing that patients with a negative CT can still have clinically important injuries
    • Sending pregnant women >24 wk gestation home without fetal monitoring

Additional Reading

  • Puskarich MA, Marx JA. Rosen's Emergency Medicine. 8th ed. Philadelphia, PA: Elsevier Saunders; 2013.
  • Raptis CA, Mellnick VM, Raptis DA, et al. Imaging of trauma in the pregnant patient. Radiographics. 2014;34:748–763.
  • Rose Zeidenberg J, Durso AM, Caban K, et al. Imaging of penetrating torso trauma. Semin Roentgenol. 2016;51:239–255.

See Also

Authors

Richard Childers
Gary M. Vilke


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