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.