Abdominal Trauma

Abdominal Trauma

• When evaluating a patient for abdominal trauma, it is necessary to think of the abdomen as three separate areas, which consist of the peritoneal cavity, pelvis, and the retro peritoneum. There are a wide variety of complex structures in each of these areas each with their own unique problems when injured.
• The organs found in each of these areas can be broken down into two basic types, solid organs and hollow organs.
• The liver, spleen, pancreas and kidneys are solid organs.
• Hollow organs are small intestine, large intestine, stomach and bladder.
• The diaphragm must also be considered when evaluating abdominal trauma as subtle diaphragmatic injuries can often be missed.
• It should be remembered that the diaphragm in expiration may rise as high as the fourth intercostals space.
• The presence of intra-abdominal contents located under the lower thoracic cage means that clinical evidence of lower chest trauma places the patient at risk for injury to intra-abdominal structures in the upper abdomen.

Penetrating Abdominal Trauma

• Penetrating intra-abdominal injuries may be caused by direct contact of the injured structure(s) with the penetrating object or by blunt/sheering forces created by cavitations that occurs along the path of a high kinetic energy penetrating object (bullet).
• In general with penetrating abdominal trauma, the amount of tissue injury is directly related to the amount of kinetic energy that the penetrating object transmits to the patient’s abdomen. The stab wound has much lower kinetic energy and generally only cause tissue injury to structures directly in its path.
• Stab wounds to the abdomen only require exploratory laporatomy in approximately 25% of patients.
• Gunshot wounds because of their much higher kinetic energy result in exploratory laporatomy in approximately 80-90% of abdominal trauma cases. The gunshot wound will not only injure structures directly in its path but because of the explosive cavitation effect may injure by secondary blunt force far from the bullets path.
• A bullet with a high level of kinetic energy may cause intraperitoneal tissue injury without ever having entered the peritoneum. Gunshot wounds therefore have much higher morbidity and mortality rates.
• Shotgun wounds represent a special case in the discussion of gunshot wounds.
• Due to the rapid decrease in velocity of the shotgun pellets and the scattering of the pellets over a wide area, less tissue injury may occur. If the victim is more than 7 yd away from the shotgun, the pellets can in most cases only penetrate fascia and subcutaneous tissue. Certainly the closer the victim is to the shotgun at the time of discharge the greater the kinetic energy delivered per pellet and more pellets will make contact with the victim increasing the potential for tissue injury. A shotgun injury at less than 3 yd range will create tremendous amounts of tissue injury.
• Explosions with fragmentation/shrapnel injuries behave similarly to shotgun injuries.
• Knowledge regarding the number of shots fired or stab wounds inflicted is useful.
• Looking at the relationships between entrance and exit wounds can give the emergency physician some estimate of the trajectory of the penetrating object which in many cases is suggestive of structures which may have been injured. This relationship is not 100% reliable as often bullets ricochet or fragment off various bony structures changing their direction of flight.

Blunt Abdominal Trauma

• The most common causes of serious blunt abdominal trauma in the United States are motor vehicle accidents and falls.
• Blunt abdominal trauma can occur through several mechanisms, which include direct blows or sudden rapid compression of the patient’s abdomen. Other mechanisms include sheering forces caused by sudden rapid deceleration such as occurs in motor vehicle accidents or falls from significant heights.
• Solid organs are injured more frequently than hollow organs in blunt abdominal trauma.
• Solid organs sustain burst type lacerations of their parenchyma secondary to the blunt force mechanisms described. The lacerations lead to hemorrhage with development of subsequent tachycardia, hypotension and other signs of hypovolemic shock.
• The most commonly injured organ in blunt trauma is the spleen (solid organ).
• Hollow organ injury occurs secondary to rupture caused by compressive forces. The rupture of hollow intra-abdominal organs causes hemorrhage and also the contamination of the peritoneum with their contents.
• Many cases of trauma demonstrate simultaneous solid and hollow abdominal organ injuries.
• Vascular attachments may be torn or avulsed leading to further hemorrhage and possible ischemic parenchymal injury.
• It should be noted that the elderly and alcoholic patient populations are at increased risk for intra-abdominal injuries because of the decreased abdominal wall tone.

Clinical Evaluation

• Historical information should be obtained regarding the events and mechanism related to the trauma from the patient, family, friends, police, paramedics and any other available resource. This information is often helpful in evaluating the potential for certain types of traumatic injuries.
• One of the key decisions to be made rapidly in the abdominal trauma evaluation is whether this patient needs an emergent operative intervention such as an exploratory laparotomy.
• Clinical signs of shock may be present during the initial evaluation or can be a delayed finding. The importance of continual reassessment of the patient cannot be emphasized enough.
• The patient’s abdomen should be carefully examined by inspection, auscultation and palpation.
• Acute abdominal tenderness is a serious sign.
• Look carefully for any evidence of ecchymosis, abrasions or penetrating traumatic wounds.
• The presence of a seat belt sign described as a linear area of ecchymosis and/or abrasion located at the previous location of the seat belt/shoulder restraint indicates the application of a significant amount of force to the patient’s abdomen. The presence of a positive seat belt sign should increase the suspicion of an underlying intra-abdominal injury.
• Ecchymosis over the patient’s flank area referred to as Gray-Turner sign suggests possible retroperitoneal hemorrhage.
• Periumbilical ecchymosis (Cullen’s sign) also is suggestive of retroperitoneal hemorrhage.
• The patient should be carefully log-rolled as a unit maintaining full cervical spine immobilization and there back carefully inspected and palpated for any evidence of trauma.
• The rectal examination should be performed while the patient is in this lateral position checking for the presence of blood, sphincter tone and in male patients whether or not their prostate is high riding.
• The presence of normal bowel sounds does not exclude the possibility of intra-abdominal trauma. Shock also can cause a secondary ileus leading to a decrease in bowel sounds even in the absence of any abdominal traumatic injury.
• It should be emphasized that physical findings may be difficult to identify in the patient with altered mental status secondary to illicit drugs or alcohol or in the patient with a spinal cord injury which can affect pain perception.
• Physical findings and mechanism of injury should direct laboratory and radiographic studies that are obtained. A rapid bedside hemoglobin should be obtained initially and serially to help evaluate the amount of blood loss and help guide any necessary blood transfusion.
• Basic abdominal trauma labs should consist of a CBC, Basic Metabolic Panel, urinalysis, PT/PTT, liver function tests, type and cross match, lipase and pregnancy test in females of child-bearing age.
• A bedside ultrasound (FAST scan) should be one of the first radiological evaluations obtained in an attempt to identify free fluid in the abdomen.
• Plain radiographs are of limited value in the evaluation of abdominal trauma.
• Plain abdominal films are helpful in identifying the presence or location of an intra-abdominal foreign body.
• A chest radiograph is helpful with regards to abdominal trauma in identifying free air secondary to a hollow organ injury or the possible herniation of abdominal structures into the thorax secondary to a diaphragmatic injury.
• Pelvic x-ray may demonstrate pelvic fractures, which should increase the clinical suspicion for retroperitoneal injury.
• Diagnostic peritoneal lavage (DPL) is an option in the absence of the availability of bedside ultrasound to evaluate for intraperitoneal injury. DPL should be reserved for the hemodynamically unstable patient in the absence of bedside ultrasound. It serves as an alternative for these patients who by virtue of their injuries are too unstable to be taken to obtain a spiral CT scan of their abdomen and pelvis. A positive DPL or FAST scan mandates operative exploration in most cases.
• The hemodynamically stable patient with suspicion of intra-abdominal injury should obtain a CT scan of the abdomen and pelvis in an attempt to identify any traumatic injuries.
• Often these patients also require CT scans of multiple other body areas simultaneously as clinically indicated.
• The advantage of spiral CT scan is its ability to clearly delineate specific injuries than either ultrasound or DPL. This greater ability at localizing and identifying specific intra-abdominal injuries gives the surgeon a preview of what to expect during surgery.
• Also the CT scan allows evaluation of the retroperitoneal area which is not evaluated by either ultrasound or DPL.

Treatment

• The primary and secondary surveys along with appropriate resuscitation should be initiated as discussed previously in this chapter.
• The patient should be placed on cardiac, blood pressure and pulse oximetry monitors.
• Supplemental oxygen should be administered to the patient, and two large bore (14 or 16 gauge) intravenous lines should be established.
• In the patient manifesting signs of hypovolemic shock, initial volume replacement with crystalloid (normal saline or ringers lactate) intravenous solutions should be initiated.
• Blood, either O negative or type-specific, should be readily available for emergent transfusion when necessary.
• When necessary, surgical consultation should be obtained as early as possible.
• Indications for laparotomy include inability to stabilize a patient with signs of continued blood loss, evidence of peritonitis, evisceration, radiological evidence of significant organ injury.
• Other treatment modalities include angiographic embolization of bleeding sites. This is especially useful in pelvic trauma and retroperitoneal hemorrhage.

Special Considerations
Diaphragmatic Injuries

• These injuries can be caused by either blunt or penetrating trauma with penetrating trauma being the most common cause.
• The most common location of injury is the posteriorlateral area of the left hemidiaphragm.
• Diaphragmatic injury secondary to blunt trauma is most commonly secondary to motor vehicle accidents.
• The most common radiographic findings on plain films are visible abdominal contents in the thorax on a chest film, indistinct diaphragmatic border, nasogastric tube in the lower left chest and focal atelectasis.
• Spiral CT scan and ultrasound have low sensitivity for detecting diaphragmatic injuries.
• In suspicious cases laparoscopy can be a useful diagnostic tool.
• In many cases diaphragmatic injuries may go undetected for years until the patient presents with delayed complications such as bowel obstruction.

Retroperitoneal Injuries

• Clinical signs and symptoms may be subtle in the presence of retroperitoneal injuries.
• Structures found in the retroperitoneum include the pancreas, kidneys, aorta, vena cava and some segments of the colon and duodenum.
• The area is difficult to evaluate by physical examination and peritoneal lavage or ultrasound does not evaluate this area.
• Spiral CT scan is the most effective method for evaluating the retro peritoneum in the stable patient.
• The mechanism of injury should increase our suspicion about possible retroperitoneal injuries.
• Duodenal hematomas or rupture are examples of possible retroperitoneal injuries that are often difficult to detect on initial evaluation and may take several hours before symptoms develop enough to arouse clinical suspicion.
• Because of the difficulty isolating retroperitoneal structures, treatment with angiographic embolization is the first treatment option.