Introduction

Well over 90% of abdominal injuries in children are the result of blunt trauma. While penetrating injuries are increasing in incidence in the adolescent population, this remains an unusual phenomenon in most Australasian communities. Abdominal injuries resulting from blunt trauma commonly affect the solid organs, particularly the liver and spleen. Overall mortality is generally <5%, but obviously this depends on injury mechanism.¹ In children with multitrauma, the subtle early clinical findings of intra-abdominal injury may be masked by change in conscious state, and chest and limb injuries, and require repeated abdominal examination.

There are unique characteristics of children that predispose them to intra-abdominal injuries. The rib cage does not extend as far distally as in the adult, the ribs are more compliant, and the abdominal wall and musculature frequently thinner and less protective. The organs are closely packed together and there is less ‘padding’ soft tissue to absorb the kinetic energy transmitted by the impact.² The upper abdominal viscera are more at risk of injury, and relatively minor forces can be transmitted, resulting in a serious disrupting injury.³

The bladder is not as well protected by the bony pelvis as in the adult, increasing the risk of bladder injury in lower abdominal trauma. Gaseous distension of the stomach from air swallowing during crying or bag–valve–mask ventilation occurs rapidly and can impair ventilation. Likewise, acute gastric dilatation or a large bladder can seriously impede clinical assessment of the abdomen. The very compliant body of the child is capable of absorbing considerable amounts of kinetic energy without external signs, yet be associated with significant internal derangement.³ Children are generally healthy, with few comorbidities and on few, if any, medications. In physiological terms, they are therefore able to compensate extremely well for blood loss.²

Early surgical involvement in treating children with abdominal injury is vital to care in the emergency department. The child with multiple injuries requires senior experienced clinicians involved in decision making during the resuscitation. Because such a patient invariably requires the involvement of several specialties, a trauma team approach, with clear leadership of the resuscitation, is imperative.

History

Obtaining details of the exact mechanism of injury cannot be over-emphasised. This often gives a clue to the potential injury pattern. Information can be obtained from witnesses, ambulance officers, family, friends, or care-givers. One member of the trauma team should be delegated to obtain this information, so that the primary survey can occur simultaneously.

Mechanisms of injury in children include pedestrians struck by motor vehicles, falls, occupants of motor vehicles involved in crashes, bicycle-related injuries, contact sports, assaults, and abuse. Falls are the most common mechanism. The events leading to the fall, and fall height and surface are all pertinent information that can usually be obtained rapidly. Information such as the aspect of the child when struck and likely speed of vehicles is useful in predicting injury patterns. Likewise, factors such as the use of restraint devices, type used, and wearing of a bicycle helmet, where appropriate, are helpful in defining the resulting injuries. Lap belts can be associated with rib and lumbar spine fractures, and upper abdominal organ injuries. Handlebar injuries may cause serious blunt intra-abdominal injuries. The resultant injuries to pancreas and duodenum can be subtle and delay the diagnosis. Hence the threshold for observation or imaging may need to be varied accordingly in children presenting with this mechanism of injury.

Small children are particularly at risk of being unsighted and backed over in driveways by reversing vehicles, and may sustain major internal injuries. The recognition of abuse as a causal mechanism in younger children and infants is important in patients with abdominal trauma. There may be minimal signs of external injury, and the reported history may suggest a minor incompatible mechanism or no history of injury at all. The emergency physician needs to maintain an index of suspicion in the infant who presents in shock or with an altered level of consciousness (see Chapter 3.2).

Other information, such as medications, allergies, and significant past history, should be obtained.

Examination

Primary survey focuses on the ABCs and may result in early interventions such as intubation or treatment of shock. The examination of the abdomen is usually delayed until the secondary survey. Where endotracheal intubation has already occurred, this invariably involves chemical sedation and paralysis. The information obtained by palpation of the abdomen in this situation is somewhat limited, and these children often require abdominal computerised tomography (CT) scanning, provided their vital signs are satisfactory and not deteriorating.

Vital signs are essential, particularly the respiratory rate, pulse rate, non-invasive blood pressure, and oxygen saturations. Attention should be given to the child’s peripheral perfusion to detect early hypovolaemia and treat prior to the occurrence of hypotension. The blood pressure needs to be measured with an appropriately sized cuff for the child’s habitus. Automated blood pressure machines, while useful in freeing staff to attend to other aspects of care, can be unreliable when hypotension exists and can result in delays in obtaining these recordings. Single vital sign recordings are of limited use, but it is the progression of recordings and the monitoring of perfusion that more accurately reflect volaemic state. In the critically ill child, pulse and blood pressure should be measured at 3–5-minute intervals.

The use of the terms unstable and stable is discouraged when conveying information regarding the child’s status to colleagues. They are non-specific and are defined differently by individual practitioners. It is more useful, when relaying the circulatory status of a child, to convey the actual vital signs, progression over time, and response to fluid to indicate volaemic state. Other parameters, such as capillary refill time, have some limitations but can add to the assessment.

In children with less severe trauma, the technique of abdominal examination is important to reliably exclude significant intra-abdominal injury clinically. Where physical examination is to be relied on as the major indicator of abdominal injury, it should ideally be performed regularly by the same observer. With serial examination and vigilance to vital signs, changes are detected early and appropriate management implemented. The aim of the abdominal examination is to elicit physical signs, such as tenderness, rebound, guarding, or rigidity, which may require evaluation by CT scanning.

Pain from injuries and other distress all add to the difficulty of abdominal assessment. Judicious and early use of parenteral opiates is safe, decreases a child’s distress, and allows a more accurate clinical assessment. Abdominal examination must be performed by gentle palpation with warm hands. There should be a brief but careful visual assessment of the abdominal wall for the distribution of any penetrating wounds, bruising, or marks (e.g. seat belt or handlebar). The presence of these warrants a prolonged observation period by admission, even for the child with no other positive findings.

Gastric dilatation may greatly impede examination as well as impair ventilation. Insertion of a nasogastric tube may facilitate examination by decompressing the stomach, while also reducing the risk of aspiration and improving diaphragmatic excursion. Aspiration of blood from the nasogastric tube usually signifies the presence of a significant intra-abdominal injury. A persistently distended abdomen after nasogastric tube insertion may signify intra-abdominal bleeding.

Information from clinical examination can usually be obtained by gentle palpation with occasional use of percussion tenderness. This technique is acceptable in children with minor trauma who require careful re-examination. Auscultation of the abdomen has limited usefulness. Rectal and vaginal examinations are rarely indicated in the child with minor abdominal trauma.

In the child with only minor injuries, the way the child moves around the emergency trolley or walks can be a useful screening tool as to whether intra-abdominal injury exists.

Investigations

General management

The assessment begins with primary survey and any life-saving interventions, while historical details are obtained simultaneously. Oxygen should be administered and vital signs monitored regularly. Vascular access is obtained early and appropriate blood samples for blood cross-matching, haematology, and biochemistry. Where there is delay in obtaining venous access, intraosseous access remains an effective method of resuscitation. Trauma series films of chest, pelvis, and lateral cervical spine should be obtained, when indicated, during the resuscitation. Views of thoracic and lumbar spine may also be required if indicated on mechanism or clinical findings. In the severely injured child, CT scanning may provide much of this information.

The abdominal examination is usually reserved until the secondary survey. Attention should be exercised to ensure that the child is warm to prevent the development of hypothermia during resuscitation.

Fluid therapy should begin with 20 mL kg^–1 of warmed crystalloid (normal saline) and repeated if required. If further fluid therapy is required after two crystalloid boluses, blood should be used in volumes of 10 mL kg^–1. The rapidity of blood loss may rarely dictate the use of O-negative or group-specific blood rather than waiting for full cross-matched blood.

Early consideration of gastric decompression with a nasogastric tube assists abdominal assessment and aids ventilation. The insertion of a urinary catheter may be necessary, depending on the requirement to aid haemodynamic monitoring of fluid resuscitation and to detect haematuria. Perineal haematoma and blood at the external urethral meatus are contraindications to routine catheter insertion and mandate retrograde urethrogram or cystogram to assess the urethral integrity. In this situation, surgical opinion should be sought.

FAST ultrasound, when available, can be performed, often within the first 20 minutes of the patient’s arrival, and may or may not show evidence of free fluid. Ongoing management is usually dictated by the haemodynamic response of the child to fluid resuscitation. CT examination is ideal but may not be possible in a very small number of exsanguinating children with deteriorating vital signs despite fluid resuscitation. In this situation, early surgical consultation regarding urgent laparotomy is required.

Surgical issues

Selective non-operative management of solid visceral injury in children is now well established. It is clear that bleeding from an injured spleen, liver, or kidney is generally self-limiting.¹¹ Success rates in excess of 90% with non-operative care mean that operative management is an exceptional event at many institutions. Pancreatic injuries, however, usually result in a higher incidence of operative intervention. Operative management is the rule for hollow viscus injuries. Some injuries, such as duodenal haematoma without evidence of perforation, may be managed without surgery. The decision about operative versus non- operative management is made by the surgeon who will have ongoing care of the child. This decision is strongly influenced by clear details regarding progression of vital signs, response to fluid therapy, and associated injuries. A non-operative approach must take place only in an institution with an available surgeon with a commitment to the injured child and dedicated paediatric intensive care or high-dependency facility.¹³ This may necessitate the transfer of the child to a regional centre.

Penetrating trauma

Penetrating abdominal injury in a child usually requires exploration by laparoscopy or laparotomy. Because the abdominal wall is often thinner than in adults, penetration into the peritoneal cavity occurs more readily. A careful assessment, including a log roll for back examination, to exclude other injuries, is necessary. Gunshot wounds should be explored in theatre. The approach to initial resuscitation is identical to that for blunt trauma. An erect chest X-ray or lateral decubitus film helps to identify the presence of free air.

Pelvic fractures

A child who sustains a fractured pelvis has been exposed to severe trauma. These are uncommon injuries in children, occurring at half the frequency as in adults.¹⁴ There are several major differences in the bony pelvis between the child and adolescent or the adult. There is greater elasticity in the sacroiliac joints and pubic symphysis, and plasticity of the bone, in the paediatric pelvis, therefore greater amounts of kinetic energy must be involved to cause fracture. Avulsion fractures occur in children and adolescents because cartilage is weaker than bone. This occurs at the physis. Greater laxity of the joints in the paediatric pelvis means that single fractures occur more commonly, as opposed to the adult pelvis, where there is the double-break concept. Fractures occurring through epiphyseal and apophyseal growth centres may result in growth arrest, leg length discrepancy, and deformity. Children also have increased capacity for remodelling.¹⁵

The common mechanisms for pelvic fracture are motor vehicle accidents and motor vehicle-pedestrian collisions, followed by falls.¹⁵

There are several classification systems for pelvic fractures. None is ideal. Torode and Zeig described four groups of pelvic fracture but failed to include isolated acetabular fractures.¹⁶ This has been modified by Silber et al,¹⁵ whose classification by mechanism of injury and description is useful (Table 3.4.1).

Table 3.4.1 Classification of paediatric pelvic fractures

Type Mechanism Description 1 Avulsion Separation through or adjacent to an apophysis 2 Lateral compression Iliac wing fractures 3 Anteroposterior compression (usually) Simple ring fractures:

4 Anteroposterior compression (usually) Ring disruption fractures:

Originally described by Torode and Zeig¹⁶ and modified by Silber et al.¹⁴

Associated injuries increase in frequency with the increasing severity of fracture type. Other skeletal injuries are common, followed by head, abdominal, and pulmonary injuries. In one large series, 19% of the total group had visceral injures. Therefore, when a pelvic fracture is identified on initial X-ray, a thorough search for other injuries must be undertaken. The management of those other injuries usually takes priority over the pelvic fracture management.

Bladder injury, while more common than in the adult, is an infrequent association. In a review of 166 children with pelvic fractures, there was one urethral disruption and two bladder contusions.¹⁵ There is a strong association of these injuries with straddle-type mechanism. Children commonly receive ‘fall astride’ injuries related to playground equipment or while riding bicycles.

In Silber’s series, 97% of children were treated non-operatively.¹⁵ The majority of these injuries (63%) were type 3 fractures. The remainder were type 2 (17%) and type 4 fractures (17%). In this series, six children died; all these deaths were due to associated injuries. The mortality rate from paediatric pelvic fractures is consistently less than 6% in recent studies.¹⁴ In a study comparing paediatric and adult fractures, the mortality rate for children was 5.7% compared with 17.5 % in the adult group. Vascular injury and exsanguination in children is rare, in contrast to in adults. This is thought to be due to the greater skeletal flexibility and the greater ability of paediatric arteries to constrict after injury.

In those children in whom blood loss is significant, early involvement of an orthopaedic surgeon and interventional radiologist is essential to optimise management. External fixation and angiography have both been used successfully, particularly in adolescent children.

Disposition

Almost all children with significant abdominal or pelvic injury require admission from the emergency department. The nature and severity of the injuries and intended management determine the most appropriate location for this to occur. Surgical colleagues involved in the ongoing care of the child should have input into this decision.

Younger children who have experienced a significant mechanism of injury (e.g. fall from great height, high-velocity motor vehicle crashes, pedestrian hit, or run over by motor vehicle) but who are apparently injury-free or have only minor injuries should also be admitted for observation (for 12–24 hours). Abdominal injuries in young children may initially have minimal or subtle signs, which become more apparent after observation and serial examination. Because of the plasticity of the paediatric skeleton, significant internal derangement can occur without obvious external evidence of trauma.

In the older child, however, it may be appropriate to discharge the patient who is injury-free or has only minor injuries. This should occur after several assessments while in the emergency department and with arrangements for follow up with a medical practitioner within 24 hours. Parents should be instructed to return earlier should a child’s symptoms change. In general, children with ongoing abdominal pain after trauma should not be discharged, regardless of negative imaging results.