O. John Ma
EPIDEMIOLOGY
The most common mechanism of blunt abdominal trauma in the United States is a motor vehicle crash.
PATHOPHYSIOLOGY
The injury pattern of blunt abdominal trauma is often diffuse. Blunt injuries involve a compression or crushing mechanism by direct energy transmission. If the compressive, sheering, or stretching forces exceed the tolerance limits of the organ tissue, then tissue disruption occurs.
Injury also can result from movement of organs within the body. Some organs are rigidly fixed, whereas others are mobile. Typical examples in the abdomen include mesenteric or small bowel injuries, particularly at the ligament of Treitz or at the junction of the distal small bowel and right colon.
Falls from a height produce solid organ injuries less commonly and hollow visceral injuries more commonly. Retroperitoneal injuries associated with significant blood loss occurs from falls because force is transmitted up the axial skeleton.
Gunshot wounds may injure the victim by having the bullet directly injure the organ or secondarily from missiles, such as bone and bullet fragments, or from energy transmission from the bullet.
CLINICAL FEATURES
SOLID VISCERAL INJURIES
Injury to the solid organs causes morbidity and mortality primarily as a result of acute blood loss.
The spleen is the most frequently injured organ in blunt abdominal trauma and is commonly associated with other intra-abdominal injuries. Kehr’s sign, representing referred left shoulder pain, is a classic finding in splenic rupture. Lower left rib fractures should heighten clinical suspicion for splenic injury.
The liver also is commonly injured in both blunt and penetrating injuries.
Tachycardia, hypotension, and acute abdominal tenderness are the primary physical examination findings associated with intra-abdominal injury.
Some patients with solid organ injury occasionally may present with minimal symptoms and nonspecific findings on physical examination. This is commonly associated with younger patients and those with distracting injuries, head injury, and/or intoxication.
A single physical examination and set of vital signs are insensitive for diagnosing abdominal injuries. Serial physical examinations on an awake, alert, and reliable patient are important for identifying intra-abdominal injuries.
HOLLOW VISCERAL INJURIES
These injuries produce symptoms by the combination of blood loss and peritoneal contamination. Perforation of the stomach, small bowel, or colon is accompanied by blood loss from a concomitant mesenteric injury.
Gastrointestinal contamination will produce peritoneal signs over a period of time. Patients with head injury, distracting injuries, or intoxication may not exhibit peritoneal signs initially.
Small bowel and colon injuries are most frequently the result of penetrating trauma. However, a deceleration injury can cause a bucket-handle tear of the mesentery or a blowout injury of the antimesenteric border.
Suppurative peritonitis may develop from small bowel and colonic injuries. Inflammation may take 6 to 8 hours to develop.
RETROPERITONEAL INJURIES
Duodenal injuries are most often associated with high-speed vertical or horizontal decelerating trauma. Duodenal injuries may range in severity from an intramural hematoma to an extensive crush or laceration.
Clinical signs of duodenal injury are often slow to develop. Patients may present with abdominal pain, fever, nausea, and vomiting, although these may take hours to become clinically obvious.
Duodenal rupture is usually contained within the ret-roperitoneum with blunt trauma.
Pancreatic injury often accompanies rapid deceleration injury or a severe crush injury. The classic case is a blow to the midepigastrium from a steering wheel or the handlebar of a bicycle.
Leakage of activated enzymes from the pancreas can produce retroperitoneal autodigestion, which may become superinfected with bacteria and produce a retroperitoneal abscess.
DIAPHRAGMATIC INJURIES
Presentation of diaphragm injuries is often insidious. Only occasionally is the diagnosis obvious when bowel sounds can be auscultated in the thoracic cavity.
On chest radiograph, herniation of abdominal contents into the thoracic cavity or a nasogastric tube coiled in the thorax confirms the diagnosis. In most cases, however, the only finding on chest radiograph is blurring of the diaphragm or an effusion.
CT is usually needed to diagnose a diaphragmatic injury. Occasionally, cavitary endoscopy or laparot-omy is necessary to make the definitive diagnosis.
DIAGNOSIS AND DIFFERENTIAL
PLAIN RADIOGRAPHS
A chest radiograph is helpful in evaluating for herniated abdominal contents in the thoracic cavity and for evidence of free air under the diaphragm.
An AP pelvis radiograph is important for identifying pelvic fractures, which can produce significant blood loss and be associated with intra-abdominal visceral injury.
ULTRASONOGRAPHY
The focused assessment with sonography for trauma (FAST) examination is an accurate screening tool for abdominal trauma. The underlying premise behind the use of the FAST examination is that most clinically significant injuries will be associated with the presence of free fluid accumulating in dependent areas.
Advantages of the FAST examination are that it is accurate, rapid, noninvasive, repeatable, portable, and involves no contrast material or radiation exposure to the patient. There is limited risk for patients who are pregnant, are coagulopathic, or have had previous abdominal surgery.
A major feature of the FAST examination is its ability to rapidly evaluate for free pericardial and pleural fluid along with a pneumothorax. It is also very useful when caring for the trauma patient who is pregnant.
A FAST-inclusive trauma protocol has been found to significantly decrease time to operative care in patients with suspected torso trauma, with improved resource use and lower medical charges.
Disadvantages include the inability to determine the exact etiology of the free intraperitoneal fluid and the operator-dependent nature of the examination. CT is the preferred diagnostic imaging study for evaluating the retroperitoneum.
Other disadvantages of the FAST examination are the difficulty in interpreting the views in patients who are obese and have subcutaneous air or excessive bowel gas, and the inability to distinguish intraperitoneal hemorrhage from ascites.
COMPUTED TOMOGRAPHY
With the increasing sensitivity and availability of CT scanners, CT has become the gold standard for the diagnosis of abdominal injury. Only CT can make the diagnosis of organ-specific abdominal injury.
A triple-contrast helical CT scan can quickly discern either contrast extravasation or the presence of air or fluid. The accuracy of triple-contrast CT as a single diagnostic study is reported to be 97% to 100% following penetrating trauma.
Advantages of CT include its ability to precisely locate intra-abdominal lesions preoperatively, to evaluate the retroperitoneum, and to identify injuries that may be managed nonoperatively, as well as its noninvasiveness.
The disadvantages of CT are its expense, radiation exposure, need to transport the trauma patient to the radiology suite, and the need for contrast materials.
DIAGNOSTIC PERITONEAL LAVAGE
Diagnostic peritoneal lavage (DPL) remains a good screening test for evaluating abdominal trauma if ultrasonography is not available. Its advantages include its relative speed with which it can be performed and low complication rate (1%).
Drawbacks include its invasiveness, the potential for iatrogenic injury, its misapplication for evaluation of retroperitoneal injuries, and its lack of specificity.
Laparotomy based solely on a positive DPL results in a nontherapeutic laparotomy approximately 30% of the time. Minor injury can produce hemoperitoneum sufficient to render DPL positive.
In penetrating trauma, DPL should be performed when it is not clear that exploratory laparotomy is indicated. DPL is useful in evaluating patients sustaining stab wounds where local wound exploration indicates that the superficial muscle fascia has been violated. Also, it may be useful in confirming a negative physical examination when tangential or lower chest wounds are involved.
In blunt abdominal trauma, the DPL is considered positive if more than 10 mL of gross blood is aspirated immediately, the red blood cell count is > 100,000 cells/µL, the white blood cell count is >500 cells/µL, bile is present, or vegetable matter is present.
The only absolute contraindication to DPL is when surgical management is clearly indicated, in which case the DPL would delay patient transport to the operating room.
Relative contraindications include patients with advanced hepatic dysfunction, severe coagulopathies, previous abdominal surgeries, or a gravid uterus.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Administer 100% oxygen and secure cardiac monitoring and two large-bore IV lines.
For hypotensive abdominal trauma patients, resuscitate with IV crystalloid fluid. Consider transfusion with O-negative or type-specific packed red blood cells in addition to crystalloid resuscitation.
Order laboratory work for abdominal trauma patients based on the mechanism of injury (blunt versus penetrating); it may include type and crossmatching, complete blood count, electrolytes, arterial blood gas, directed toxicologic studies, coagulation studies, hepatic enzymes, and lipase.
Table 167-1 lists the indications for exploratory laparotomy.
If organ evisceration is present, then cover it with a moist, sterile dressing prior to surgery.
The evolution of nonoperative therapy has been greatly advanced by the evolution of CT. CT not only can make the diagnosis of solid visceral injury but can also often rule out other injuries requiring surgery.
For the hemodynamically stable blunt trauma patient with a positive FAST examination, further evaluation with CT may be warranted prior to admission.
For an equivocal stab wound to the abdomen, surgical consultation for local wound exploration is indicated. If the wound exploration demonstrates no violation of the anterior fascia, the patient can be discharged home safely.
Local wound exploration is only appropriate for anterior abdominal stab wounds and not for those in the flank or back.
TABLE 167-1 Indications for Laparotomy
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide 7th ed., see Chapter 260, “Abdominal Trauma,” by Thomas M. Scalea, Sharon Boswell, Bonny J. Baron, and O. John Ma.