Chapter 26: Abdominal Trauma

• Blunt abdominal trauma is proportionally more common in children and results in more injuries and deaths than penetrating trauma.

• The spleen and liver are the most commonly injured organs as a result of blunt abdominal trauma. Liver injuries constitute the most common cause of death.

• Computed tomography (CT) scan provides diagnoses of abdominal injuries. However, CT scan is not without risk and must be used judiciously using the ALARA standard (as low as reasonably achievable).

• Perforations of the duodenum and proximal jejunum are the most common intestinal injuries and are usually associated with lap belt or bicycle handlebar injury.

Trauma is the most common cause of death in children. Abdominal trauma accounts for close to 200,000 visits to US emergency departments each year.¹ Serious abdominal injuries account for approximately 8% of admissions to pediatric trauma centers. Only 15% of these injuries require surgery and the majority of these are for penetrating wounds.

Abdominal trauma is the third leading cause of traumatic death, behind head and thoracic injuries in children.

Blunt abdominal trauma is proportionately more common in children and results in more injuries and deaths than penetrating trauma. Blunt trauma accounts for 85% of pediatric abdominal trauma. Penetrating abdominal trauma accounts for approximately 15% of the total cases and 6% of these will die primarily from the penetrating wound.

Children are susceptible to different injury patterns than adults. Blunt trauma from motor vehicle collisions (MVCs) causes more than half of the abdominal injuries and is the most lethal. Penetrating injuries in the pediatric population are increasing particularly in young adolescents. Accidental impalement occurs more often in children younger than 13 years and may involve such diverse items as scissors or picket fences.

Management of pediatric abdominal trauma requires a coordinated effort between the emergency physician, trauma surgeon, and pediatric referral center. Immediate stabilization and transfer of the most severely injured children to an appropriate trauma center when indicated will result in greatly improved outcomes.^2,3

Motor Vehicle Collisions

Multisystem trauma, along with abdominal injury, is common when an automobile strikes a child (Table 26-1). Waddell's triad (Fig. 26-1) demonstrates a pattern of pediatric pedestrian injury with impact first to the upper leg, then chest and abdomen, followed by head. The head and extremity components of Waddell's triad should not divert attention from intra-abdominal injury that may include life-threatening hemorrhage. In countries in which motorists drive on the right side of the road, the most common injuries are on the left side as children are often struck crossing the street, and frequently result in splenic injuries. The lap belt complex in the restrained child is characterized by ecchymosis, abrasion, or erythema in the pattern of a lap belt (seat belt sign) across the abdomen (Figs. 26-2 and 26-3) and flanks (Grey–Turner sign) and occurs in up to 10% of restrained children. The injury is thought to occur because of an improperly applied restraint that allows the lap belt to ride up and compress the abdomen as the child slides forward under the belt. Presence of the “seat belt sign” always warrants further evaluation and has been associated with increased risk of gastrointestinal injury.^4,5

Bicycle Crashes, Sports Injuries, and Falls

Head trauma remains the predominant injury in bicycle crashes, although abdominal injury can occur if the child is impacted by the handlebars or falls to the ground. Handlebar injuries (Fig. 26-4) are particularly obscure, as most children show no serious sign of injury for hours to days after the impact. The mean elapsed time to onset of symptoms is almost 24 hours and as many as one-third are discharged home initially. The seriousness is illustrated by a mean length of stay exceeding 3 weeks for children who require admission for a handlebar injury. Traumatic pancreatitis, often with pseudocyst formation, is the most common handlebar injury followed by injuries to the kidneys, spleen, and liver, duodenal hematoma, and bowel perforation. Consult a trauma surgeon and observe children with a suspicion for this injury. Sports-related trauma typically produces isolated organ injury because of a direct blow to the abdomen. The spleen, kidney, and gastrointestinal tract are particularly vulnerable. Falls rarely cause isolated serious abdominal injury unless there is a direct blow to the abdomen or fall from great height, usually twice their height.

Child Abuse

Significant abdominal injury occurs in approximately 5% of child abuse cases. The diagnosis can be obscured by the inherent delay in seeking treatment, the surreptitious nature of the visit, and the lack of external signs of trauma in up to one-half of these patients. Common patterns of injury are to the liver and spleen with associated rib fractures.

Certain anatomic features predispose children to multiple rather than single injuries. Proportionally larger solid organs, poorly muscled protuberant abdomen, and flexible thin ribs contribute to the increased incidence of significant abdominal injury and potential for hemorrhage. The diagnosis of a major intra-abdominal hemorrhage may be delayed because children have the capacity to maintain normal blood pressure and pulse rate for age, even in the face of significant blood loss. External signs of injury, abdominal tenderness, and absence of bowel sounds seldom give clues to the ultimate need for surgery. Abdominal distention may be because of hemoperitoneum, peritonitis, or most commonly, gastric distention from crying, and air swallowing. This can confound the examination by masking or mimicking serious abdominal injury or bleeding. Severe dilation can result in respiratory compromise because of interference with diaphragm motion, gastric aspiration, or vagal dampening of the normal tachycardic response. In children, the primary response to decreased cardiac output is increased heart rate; therefore, vagal dampening can lead to precipitous circulatory collapse in the presence of unrecognized hypovolemia.

General Principles

A team approach in the evaluation and treatment of abdominal injuries, that includes the emergency physician, trauma surgeon, anesthesiologist, and surgical subspecialists, is ideal. In reality, many emergency physicians find themselves as the only physician initially and must approach the injured child in a systematic way, utilizing consultants expeditiously. Blunt abdominal injuries rarely require surgical intervention, whereas penetrating trauma frequently does. Nevertheless, all unstable patients need immediate surgical consultation.

The basic principles of trauma evaluation and resuscitation should be followed in all cases of abdominal trauma. Evaluation of the abdomen is included in both the primary and secondary surveys. The following interventions are particularly important:

• Insert a nasogastric or orogastric tube to decompress the stomach and to check for blood or bile. Insert an orogastric tube if there is any suspicion of head trauma or basilar skull fracture.

• Place a urinary catheter to check for blood and urinary retention, if there is no gross blood at the meatus. Obtain a urinalysis.

• Complete a rectal examination to check for blood, prostate position in males, and rectal tone.

• Keep the child NPO because of the possibility of surgery or development of paralytic ileus.

• Blood should be obtained for type and cross-match, electrolytes, CBC, serum amylase, and liver transaminases.

The mechanism of injury is important and guides the secondary survey and the ordering of specific tests or procedures. It is always important to log roll the patient to inspect the posterior torso for additional wounds. External injuries such as abrasions, lacerations, bruising, and characteristic markings such as tire tracks and seat belt marks should be noted.

Children respond differently to trauma and stress. A traumatized child may be more difficult to examine and may not show the familiar signs of impending demise as seen with adults. History may be limited and the child's reaction to pain may be difficult to assess. Designate a team member or the parent or caregiver at the bedside to take care of the child's emotional needs and to comfort them through the ordeal of trauma evaluation and treatment. Over the past decade, many pediatric trauma centers have instituted policies on family member presence for trauma and pediatric resuscitation.^6–8

Penetrating Abdominal Trauma

The diagnosis and treatment of penetrating abdominal injuries in children does not differ greatly from that for adults, and initial management is not dependent on identifying any specific injury. The hollow organs, because of their large volume, are most commonly injured, followed by the liver, kidney, spleen, and major vessels.

In children, the abdomen begins at the nipples, so penetrating wounds between the nipples and the groin potentially involve the peritoneal cavity and should be considered contaminated. Location, size, and possible trajectory of entrance and exit wounds help to identify potential underlying injuries. Surgical evaluation, wound debridement, and possible exploration, along with broad-spectrum intravenous antibiotics, are necessary in all but the most minor of wounds. At a minimum, the following should be performed with significant penetrating abdominal trauma: placement of a nasogastric or orogastric tube; placement of a urinary catheter; upright and lateral (if possible) chest radiograph; supine, upright, and cross-table abdominal radiographs; obtain a CT scan of the abdomen with IV contrast for deep-penetrating stab wounds and all gunshot wounds unless their clinical condition is unstable and they need to go directly to the operating room. Gunshot wounds to the abdomen require immediate exploration. Most enter the peritoneal cavity and injure organs directly or indirectly through kinetic energy dissipation. The high morbidity and mortality associated with gunshot wounds is due to the destructive force of the missile and its fragments, rapid blood loss, complicated surgical repair, and postoperative complications.

Stab wounds pose the greatest threat to blood vessels. Commonly injured vessels include the aorta, inferior vena cava, the portal vein, and hepatic veins. However, stab wounds enter the peritoneal cavity only one-third of the time and only one-third of these require a visceral repair.

Local exploration may be possible to rule out peritoneal penetration in minor stab wounds. Conservative management can be entertained if the patient meets the following criteria:

• No sign of shock or peritonitis with observation for 12 to 24 hours

• No blood in the stomach, rectum, or urine

• No evidence of free abdominal or retroperitoneal air on x-ray

• No history or evidence of bowel or omental evisceration

• Close observation with surgical consultation

Blunt Abdominal Trauma

Both isolated abdominal and multisystem trauma present challenges in the pediatric patient because information is inherently difficult to obtain. Multiple other injuries may overshadow often subtle early abdominal findings and the physical examination may be only 55% to 65% accurate. Minor mechanisms, such as falling from 2 ft to the ground, can still result in significant injury with minimal symptoms. Therefore observation, as well as repeat vital signs and serial abdominal examinations, may be warranted. Laboratory and radiologic studies may be necessary depending on clinical status, mechanism of injury, and suspicion for injury on physical examination.

Radiographs of the chest (supine or preferably upright posteroanterior plus a lateral) and supine abdomen and pelvis can give important clues to the diagnosis of abdominal injury (Table 26-2).

Laboratory Evaluation (Diagnostic Studies)

The child with blunt trauma is at high risk for intra-abdominal injury if any of the laboratory or physical examination findings listed in Table 26-3 are present.⁹ Hemoglobin and hematocrit are seldom useful early in the evaluation, but may be valuable for comparison to baseline later in the management of the patient. However, if the initial hematocrit is <30% with other signs of impending shock, this suggests significant hemorrhage.⁹ An initial hematocrit <24% is associated with high mortality, and transfusion should be initiated immediately.

A persistently distended abdomen after nasogastric tube placement, hemodynamic instability not immediately responsive to fluid resuscitation, recurrent hypotension, or signs of peritoneal irritation warrant immediate surgical intervention by a surgeon experienced in pediatric abdominal injuries.

Computed Tomography

Computed tomography (CT) scan has eliminated much of the difficulty surrounding the diagnosis of abdominal injuries and is the procedure of choice for stable trauma patients. Specialized studies should be ordered in consultation with the trauma surgeon to avoid unnecessary delay in definitive treatment. Indications for abdominal and pelvic CT scan are listed in Table 26-4. CT scan is useful for evaluation of the liver, kidney, spleen, retroperitoneum, and, to a lesser extent, gastrointestinal injuries. CT scan identification of pancreatic injury, diaphragm injury, and bowel perforation are much less sensitive and warrant a high index of suspicion with serial abdominal examinations to rule out occult injury.

Radiation exposure is the greatest risk associated with CT scan.¹⁰ Abdominal CT scan carries a significant lifetime cancer mortality risk with radiation-attributable risks from a single abdominal CT scan within the first and tenth years of life estimated at 1/550 and 1/700, respectively.^11,12 Variation in practice with respect to CT scan of the child with blunt abdominal trauma persists. Clinical decision rules are necessary to reduce variability in medical management by providing evidence-derived guidelines for clinical care; thereby, decreasing unnecessary radiation exposure.^13,14

The Pediatric Emergency Care Applied Research Network (PECARN) recently derived a prediction rule to identify children at very low risk for intra-abdominal injuries undergoing acute intervention and for whom CT can be obviated.

This clinical prediction rule consists of seven patient history and physical examination variables, easily available to clinician. The PECARN prediction rule for IAI was derived in over 12,000 children and had excellent performance characteristics with a negative predictive value of 99.9% and sensitivity of 97%; however, external validation of the rule is pending. The clinical prediction rule included the following seven variables in descending order of importance:

• No evidence of abdominal wall trauma or seat belt sign

• Glasgow Coma Scale Score > 13

• No abdominal tenderness

• No evidence of thoracic wall trauma

• No complaints of abdominal pain

• No decreased breath sounds

• No vomiting

In instances when abdominal CT is obtained and is negative, it might be safe to discharge a stable child home due to the high negative predictive value of abdominal CT for detection of intra-abdominal injury.^15,16

Use of oral and intravenous contrast media has traditionally been thought to increase the sensitivity of abdominal CT scan. However, oral contrast is rarely used in the trauma setting because of the technical difficulty of administration and increased waiting time before scanning, risk of aspiration, and apparent limited value because of frequent lack of bowel opacification.¹⁷

Diagnostic Peritoneal Lavage

Close observation, serial physical examinations, and particularly abdominal CT scan are utilized to the virtual exclusion of peritoneal lavage in pediatric patients. Diagnostic peritoneal lavage (DPL) may still be useful if these other modalities are unavailable or the child must undergo immediate general anesthesia for other injuries. Under these circumstances, DPL can often be performed in the operating suite. However, the usefulness of DPL remains questionable. It is neither organ-specific nor injury-specific, and cannot reliably assess retroperitoneal injury, and the decision to operate for liver or splenic injuries is not based on the amount of intraperitoneal blood in children. In addition, the introduction of air and fluid into the abdomen and the resulting peritoneal irritation make subsequent physical and radiographic examinations more difficult.

The technique for DPL in children is similar to that for adults, although a small supraumbilical incision to avoid the bladder is preferred in young children over the usual infraumbilical approach.

Abdominal Ultrasound

Bedside ultrasound (US) is more readily available and has significantly reduced the need for DPL. It is particularly useful in the unstable patient as an immediate triage tool and adjunct to the physical examination. As such, it is best used for detecting intra-abdominal injuries that require immediate attention (such as in the setting of hypotension) rather than for a definitive diagnosis.^18–21 It is also useful when CT scan is not available and its greatest utility is in detecting intraperitoneal hemorrhage and pancreatic injuries. Overall, CT scan is more sensitive than US at detecting intra-abdominal injury in children.^22–24 In addition, a highly experienced ultrasonographer is required to improve the sensitivity of the pediatric abdominal US. Abdominal US has 66% to 83% sensitivity for the detection of hemoperitoneum in the pediatric trauma patient and CT scan is recommended in the presence of a positive US.²⁵

The use of bedside US has become part of the core emergency medicine curriculum and is often taught using the FAST method. The FAST examination evaluates up to six areas of the abdomen with the principal objective of identifying hemoperitoneum. Children who are hemodynamically unstable with abdominal trauma will require laparotomy regardless of the US and those that are stable are often managed nonsurgically even with abdominal organ injury. Therefore, the exact role of US in assessing pediatric abdominal trauma is still being evaluated.

Solid Organs

Spleen

With blunt trauma, the spleen is the most frequently injured solid organ and second only to the liver in lethal injury. Penetrating injuries of all types can cause splenic injury and, as with liver stab wounds, it is often difficult to determine the extent of underlying injury based on the external signs of trauma. Mononucleosis, common in children, can result in splenic enlargement and predispose to splenic rupture with even mild impact. Patients with this condition should be warned about contact sports or any activity that could cause a blow to the abdomen until the spleen has returned to normal size, a minimum of 4 to 6 weeks.

Although diffuse abdominal pain may be the presenting complaint, typical findings with splenic injury are left upper quadrant abdominal pain, radiating to the left shoulder (Kehr's sign), associated with palpable tenderness on examination. Significant tenderness in the left upper abdomen and/or splenic enlargement should prompt surgical consultation and consideration of a CT scan. Frank splenic rupture may lead to shock and posttraumatic cardiac arrest. Persistent unexplained leukocytosis or hyperamylasemia also suggests splenic injury.

Abdominal CT scan is the study of choice to identify splenic injury. Once a splenic injury has been identified in the stable patient, management is focused on salvaging the spleen. The thick elastic splenic capsule in children and the usual transverse orientation of lacerations parallel to the vessels commonly results in spontaneous cessation of bleeding and allows nonsurgical management in 90% of cases.

Conservative management includes initial hospitalization for a few days of bed rest for grade 1 or 2 injuries and longer for higher-grade injuries, followed by a regimen of limited activity.

Current data suggest it is safe to discharge stable patients within 3 days of splenic injury and lift restrictions on physical activity within 8 weeks of injury.^26,27

Although spontaneous healing of splenic lacerations and subcapsular hematomas occur in the overwhelming majority of cases, delayed spontaneous rupture can occur at any time and is most common on the third to fifth day. The commitment to conservative management includes close observation and frequent examination.

Children who develop hypotension not responsive to volume resuscitation require surgery. There is a marked increase in infection and a 65-fold increase in lethal sepsis in children with splenectomy, particularly with encapsulated organisms (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, and Escherichia coli). The pneumococcal and H. influenzae (HIB) vaccines should be given to any patient undergoing partial or complete splenectomy, even though antibody response may be inconsistent and temporary.

Liver

The liver ranks second among solid abdominal organs for major hemorrhage and significant injury, but it is the most common source of lethal hemorrhage. Mortality from serious liver injuries may be as high as 10% to 20%. However, the majority of liver injuries in children is minor and remains undetected unless discovered incidentally by abnormal liver enzymes or imaging studies. Serum aspartate aminotransferase (AST) greater than 200 U/L and alanine aminotransferase (ALT) greater than 125 U/L have been associated with intra-abdominal injury (Table 26-3).⁹ CT scan has revolutionized the diagnosis of liver injury and accounts for the increased recognition of this problem.

Mechanisms of injury are similar to those in splenic trauma. Symptoms depend largely on the extent of injury and range from nonspecific diffuse abdominal pain to posttraumatic cardiac arrest. Significant tenderness in the right upper abdomen and/or liver enlargement should prompt surgical consultation and CT scan evaluation.

Children with liver injuries who are not in shock or who respond to volume resuscitation rarely require surgery to control bleeding. However, nonsurgical management is not without complications. Those requiring late laparotomy have transfusion requirements greater than 50% of total blood volume (TBV) during the first 24 hours after injury and bleeding into the biliary tract (hematobilia) is not uncommon. Conservative management includes careful monitoring of vital signs, serial abdominal examinations, and serial hematocrit measurements.

Large stellate liver lacerations and subcapsular hematomas that have eroded through Glisson's capsule rarely stop bleeding without surgery. Direct suturing and drainage can manage most hepatic lacerations. In preparation for surgery, circulating blood volume should be restored since rapid hemorrhage can occur as blood clots are evacuated during repair.

Pancreas

The pancreas is rarely seriously injured in blunt pediatric trauma because of its deep position in the upper abdomen. However, it is in a fixed position anterior to the vertebral column and vulnerable to a direct blow to the upper central abdomen as seen with bicycle handlebar injury (Fig. 26-4). Pancreatic injuries are difficult to diagnose and signs such as elevated amylase and lipase may take up to 72 hours postinjury to present.

Traumatic pancreatitis without major pancreatic injury is most common, followed by pancreatic hematomas and, rarely, transection of the body or duct. Pancreatic transections often lead to pancreatic pseudocyst formation within 3 to 5 days and result in chronic intermittent attacks of abdominal pain, nausea, vomiting, and weight loss. Acutely, the leakage of pancreatic fluid into the lesser peritoneal sac causes a chemical peritonitis and pancreatic ascites. The classic triad of epigastric pain radiating to the back, a palpable abdominal mass with or without acute peritonitis or ascites, and hyperamylasemia are rarely detected in children.

CT scan may help identify severe pancreatic injury or evidence of pancreatic edema as an early indication of trauma but is not as helpful in determining management. US may be more useful but is also unlikely to change the early management. Simple traumatic pancreatitis is treated similarly to other types of pancreatitis with bowel rest, nasogastric suction, intravenous fluids, and pain medication. Severe pancreatic injury will typically require surgical drainage with repair or partial resection of the pancreas. Pancreatic pseudocyst treatment involves 6 to 8 weeks of total parenteral nutrition followed by a surgical drainage procedure.

Abdominal Wall

The muscles of the abdominal wall include the rectus abdominis anteriorly; the internal oblique, external oblique, and transversalis laterally; and posteriorly the erector spinae (sacrospinalis) muscle group, quadratus lumborum, latissimus dorsi, serratus posterioinferior, and the psoas (located deep and posterior). Hematomas of any of these muscles can occur as well as concomitant injury to the spine and other skeletal structures. The psoas muscle is particularly susceptible to hematoma formation, even with minor trauma, in patients with a bleeding diathesis such as hemophilia, or those on warfarin.

Tenderness, bruising, swelling, or a mass of the abdominal wall may indicate a hematoma or simply a contusion. However, certain types of ecchymosis (such as the “seat belt sign”) are indicative of intra-abdominal injury and the onset may occur several hours after the trauma. Grey–Turner sign is an ecchymosis in the abdominal or flank area and may represent a retroperitoneal hematoma. Cullen's sign is a bluish discoloration around the umbilicus and may represent an intraperitoneal hemorrhage. Abdominal wall injuries, other than large lacerations, are typically self-limited and consideration for other underlying injury is more important, as outlined in the previous sections. Differentiation between abdominal wall and deeper injury can be difficult, so a low threshold for abdominal CT scan is warranted.

Careful instructions should be given at discharge. Patients and caregivers are instructed to watch for vomiting, increasing pain, abdominal distention, hematuria, and fever. Ensure close follow-up for reexamination within 24 hours for any significant abdominal wall injury.

Hollow Organs

Hollow visceral organs are injured in only 1% to 5% of children with blunt abdominal trauma. Of those requiring laparotomy, up to 16% may have such injuries. Perforations of the duodenum and proximal jejunum are the most common and usually associated with a lap belt or bicycle handlebar injury. Penetrating trauma is more obvious and more likely to show early signs of injury, such as free air.

Without obvious evidence of free air on radiographs, the diagnosis of a perforated viscus in blunt trauma can be difficult. Tenderness may initially be localized and slowly worsen over 6 to 12 hours, accounting for the time necessary for peritonitis or obstruction to occur. Abdominal CT scan is not particularly sensitive for these injuries, and repeated physical examinations remain the most reliable indicator of enteric disruption. Surgical consultation should be obtained early in the management of these patients. Once the suspected diagnosis of perforated abdominal viscus has been made, treatment is straightforward with laparotomy to repair the injury. Most injuries can be repaired primarily; however, colon perforations often require a diverting colostomy.

Intramural hematomas of the duodenum or jejunum can cause symptoms of intestinal obstruction with pain, bilious vomiting, and gastric distention. The diagnosis can be made with US or upper GI series, which reveals the “coiled spring” sign. This problem rarely requires surgery. It may cause traumatic pancreatitis with involvement of the ampulla of Vater. Treatment is conservative and supportive including nasogastric suction and parenteral nutrition for up to 3 weeks.

When a large abdominal wall defect is present, as with a large stab wound or close-range shotgun wound, evisceration can occur. The bowel should be kept moist with saline-soaked gauze and not allowed to assume a dependent position that would increase edema of the bowel wall.

Evaluation and treatment of children with suspected abdominal trauma is challenging. Physiologic characteristics of children make vital signs and physical examination less predictive of serious injury than in adults. Therefore, other diagnostic clues such as mechanism of injury and maintaining a high suspicion for common injuries are paramount. Consult a trauma surgeon or transfer patients to an appropriate trauma center if you are concerned that the child has an intra-abdominal injury. An awareness of useful diagnostic tests such as abdominal CT scan and their limitations is also important. Finally, it is wise to identify resources for treatment of pediatric trauma well in advance. The ability to provide definitive care in an efficient manner through trauma teams or expeditious transfer to a trauma center optimizes the chances of survival and limitation of morbidity.

Special thanks to Wendy Ann Lucid and Todd Brian Taylor for their contributions to the previous edition of this chapter.