David B. Burbulys, MD
An 8-year-old boy who was riding downhill on a bicycle crashed into a tree and was transported to the local trauma center by emergency medical services. On arrival he was brought to the pediatric emergency department, where the paramedics report that the bike handlebars struck the child’s abdomen. The boy reports dizziness and vomits several times. Initial vital signs show a heart rate of 135 beats per minute, blood pressure of 105/60 mm Hg, oxygen saturation of 98% on room air, and a respiratory rate of 24 breaths per minute. The abdomen is flat but tender to palpation in the mid- epigastric region and left upper quadrant.
1. What are the most common mechanisms of intra-abdominal injury in children?
2. What are the diagnostic studies used to evaluate abdominal trauma?
3. What is a simple rule for establishing the lower limit of normal blood pressure in children when assessing a child for shock?
4. What are the basic components of the treatment of shock that occur after abdominal trauma?
Abdominal trauma is the leading preventable cause of fatal injury in trauma patients. Death results when the extent and nature of abdominal injuries are neither appreciated nor appropriately managed, fluid replacement is inadequate, and airway maintenance and surgical intervention are not implemented soon enough. Primary abdominal trauma is the third leading cause of traumatic death, after head and thoracic injury. Clinicians should be knowledgeable about mechanisms of injury that result in abdominal trauma, early manifestations of shock, and methods of aggressive treatment of hemorrhagic shock.
Twenty-five percent of children who sustain multisystem trauma have significant abdominal injury, and 9% die from abdominal-associated trauma. The risk of death is higher with simultaneous head and abdominal injury than with the occurrence of either injury alone. Blunt-force mechanisms are responsible for nearly 85% of abdominal injuries, with the remainder resulting from penetrating injuries. Examples of blunt-force mechanisms, presented in order of frequency from most to least frequent, include motor vehicle crashes, which also are the most lethal; pedestrian versus automobile collisions; falls; bicycle injuries; sports injuries; and direct blows from abuse and assault. Injuries to the spleen and liver predominate, followed by injuries to the kidney, bowel, and pancreas. In patients with multiple injuries, the incidence of trauma involving pelvic bones and organs (eg, bladder, ureter, iliac vessels) is also high. A straddle injury (eg, a fall that occurs when climbing over a fence) can also result in abdominal and pelvic trauma.
Pain, tenderness, ecchymoses, and peritoneal signs (ie, voluntary or involuntary guarding, rebound tenderness) are among the more reliable signs of pathology, whereas abdominal distention and absence of bowel sounds are less consistent markers of injury. (See Box 76.1 for signs and symptoms suggestive of abdominal trauma.) It is particularly important to note that no sign is completely reliable and that acute hemorrhage into the abdomen does not result in peritoneal irritation initially. A high index of suspicion must be maintained in situations in which it is warranted based on the severity of the mechanism of injury, despite minimal initial physical findings. Unexplained hypotension or shock mandates further investigation with ultrasonography or computed tomography (CT) to assess for intra-abdominal hemorrhage.
Box 76.1. Signs and Symptoms Suggestive of Abdominal Trauma
•Peritoneal signs (eg, absent or diminished bowel sounds, rebound tenderness, guarding)
•Seat belt marks
•Urine, stool, or nasogastric aspirate positive for blood
•Unexplained hypotension or other signs of hypovolemic shock
Blunt trauma largely involves injury to solid, not hollow, intra- abdominal organs (ie, spleen and liver rather than small bowel) for a variety of reasons. First, the rib cage is flexible in children. As a result, rib fractures are less likely to occur, thereby reducing the potential for penetration of hollow abdominal organs by broken ribs. Second, children have less well-developed abdominal musculature and less adipose tissue than adults and larger organs relative to overall body size. Thus, in children blunt force is more easily and more diffusely transmitted to the solid organs. Third, because the diaphragm is oriented more horizontally in children than in adults, the liver and spleen lie more anteriorly and caudally within the abdomen.
It is important to emphasize that abdominal injury may result in excessive blood loss. The pathophysiology of hemorrhagic shock is discussed in detail in Chapters 74 and 75. The liver and spleen are highly vascularized organs that bleed profusely when lacer-ated. Even the accumulation of a subcapsular hematoma without rupture may cause a profound drop in hematocrit. Because intra-abdominal organs are not directly visible when a patient is examined, signs and symptoms of injury are not always obvious. Therefore, hemorrhagic shock should always be suspected in patients with abdominal trauma. Likewise, large volumes of blood can accumulate in the pelvis and retroperitoneum, and because of their proximity to the abdomen, they should always be considered as a reservoir for hemorrhage in abdominal as well as pelvic trauma.
Physicians should be familiar with the most common patterns of abdominal injury and should consider the possibility of specific injuries. Any solid abdominal organ can be injured by any mechanism, whether blunt or penetrating. The spleen is the most common intra-abdominal organ injured by a blunt force. Hepatic injuries are the most common fatal abdominal injuries, although they are less frequent than splenic injuries. The right lobe of the liver is injured more frequently than the left lobe.
Injuries to hollow viscera, such as the stomach and intestines, which represent only approximately 5% to 15% of injuries from blunt forces, are difficult to diagnose and often present late only after peritonitis manifests. Three mechanisms result in injury of hollow structures: “crush” between the anterior wall of the abdomen and the vertebral column; deceleration, which causes shearing of the bowel from its mesenteric attachments; and “burst,” which occurs when an air- or fluid-filled loop of bowel is closed at both ends at the time of impact. Peritonitis may manifest within 6 to 48 hours secondary to fecal spillage or devascularization as the result of any of these mechanisms. Occasionally, a diagnosis of hollow viscera injury is made incidentally or may be delayed more than 48 hours, which reinforces the necessity of observation and serial examinations. Duodenal and pancreatic injuries are examples of potentially delayed diagnoses that can have grave consequences. Leakage of bile and enzymes may activate autolysis of the pancreas and result in sepsis syndrome.
Determining which organ or organs may be injured as the result of abdominal trauma is difficult. Up to 50% of significant injuries are missed on initial physical examination. Children are often uncooperative or unable to assist with the evaluation. Physicians tend to focus on injuries to the extremities, pelvis, face, or chest that are painful and distracting to children and more clinically obvious to the examiner. Initial clinical impressions may be incorrect, causing delayed diagnosis or unnecessary surgical exploration.
The history should focus on the mechanism of injury and the physiologic response of the child, especially in the pre-hospital setting (eg, initial hypotension, tachycardia, cyanosis; Box 76.2). A poor history concerning the circumstances of the injury may contribute to a delayed diagnosis.
As stated previously, an abnormal physical examination may not always be indicative of pathology. Clinicians should avoid relying on physical examination alone as a predictor of abdominal injury. Studies have demonstrated that patients with and without proven injuries often showed no significant differences with respect to physical findings. In particular, children with abusive abdominal trauma often have no cutaneous evidence of bruising, especially immediately after the injury is inflicted (see Chapter 142). Thus, definitive evaluation of the abdomen is mandated for patients with significant mechanism of injury. Such evaluation often includes point of care ultrasonography, rapid CT, formal ultrasonography, diagnostic peritoneal lavage, laparoscopy, or laparotomy.
Vital signs should be monitored and trends followed. In children, the range for normal heart rate, respiratory rate, and blood pressure is age dependent. A simple rule for calculating the lower limit of normal systolic blood pressure is 70 + (2 age in years). Physicians should always remember that a drop in blood pressure is a very late sign in the development of shock in children (see Chapters 74 and 75).
Serial abdominal examinations increase the likelihood of detecting a previously missed condition. Inspection of the abdomen to evaluate for ecchymoses, distention, tire tracks, penetrations, or paradoxical motion should occur first. Auscultation for bowel sounds follows this inspection, and palpation should be done last. Palpation should be done in all 4 quadrants to elicit tenderness, rebound, and guarding. If a hepatic or splenic injury is initially suspected, palpation should be minimized to avoid further hemorrhaging.
Box 76.2. What to Ask
•How was the child injured?
•How long ago did the injury occur?
•What parts of the body were injured?
•Did the child receive any treatment before coming to the hospital, and what was the response?