Trauma is the leading cause of morbidity and mortality in children older than 1 year.¹ Blunt abdominal trauma in children is relatively infrequent, accounting for approximately 2% to 8% of all trauma cases in children.^{2, 3 and 4} However, published mortality rates are as high as 13% to 45%, with concomitant traumatic brain injury implied as the major factor in fatal cases.^{4, 5 and 6} Intra-abdominal injuries from blunt trauma may be difficult to recognize clinically due to the inability of young patients to communicate effectively^5,7 or due to loss of consciousness or altered mental status. The majority (approximately 80%) of children able to be assessed following trauma present with abdominal pain.⁸ Whereas victims of high-velocity injuries—for instance, motor vehicle accidents or falls from significant heights—tend to present immediately to medical centers for care, children injured by lesser insults or by nonaccidental trauma (NAT) often receive delayed care.^4,7,9 In the pediatric population, differentiation between NAT and trauma becomes very important to ensure the future well-being of the child. The different patterns of injuries seen in these two distinct pediatric groups are discussed in this chapter as well as the appropriate diagnostic imaging for blunt abdominal trauma in the child.

Diagnostic radiologists, along with our pediatric clinical colleagues, have a critical role in protecting children from maltreatment. It has been estimated that the rate of abuse is approximately 4.9 children per 1,000,¹⁰ and some studies show that up to 17% of hospital admissions for abdominal trauma in infants are attributable to NAT.^11,12 Intra-abdominal injuries in children less than 4 years of age are more often caused by NAT than by accidents,^4,7,9,13 and as mentioned above, the presentation of affected children to health care centers is more likely to be delayed than when a child is injured accidentally. Intra-abdominal injuries from NAT are often more severe than are those seen with accidental trauma, with higher rates of emergent surgical exploration^5,11 and mortality^2,5,14 in NAT cases. Risk factors for abdominal trauma due to NAT are the same as other types of injuries caused by NAT and include poverty, single-mother families, and male gender.¹¹ Table 18.1 summarizes the types of injuries that are specific for NAT.¹⁵

Different patterns of intra-abdominal injuries have also been observed in children presenting after NAT compared with accidental abdominal trauma. Solid abdominal organs are usually injured with high-velocity accidents such as motor vehicle accidents and falls from heights above 10 feet, with the whole-body inertia leading to a “burst injury” (Fig. 18.1). In contrast, there is a disproportionately high rate of injuries to the pancreas and hollow viscus organs caused by NAT, due to a direct impact to the abdomen (see Table 18.2; Fig. 18.2).^4,8,9,14 The duodenum and proximal jejunum are the most commonly seen hollow viscus injuries in NAT victims, although stomach, bladder, and large bowel injuries have also been reported.^13,16

The observed injuries must be assessed in the context of the reported mechanism of injury. In cases of inflicted trauma, the injuries are commonly inconsistent with the type of trauma reported by the infant or child’s care provider.^7,17 For instance, a low-level fall is a frequently provided explanation in cases of abuse; however, hollow viscus injury is exceedingly rare in such falls.^16,18 A retrospective literature review by Huntimer et al.¹⁹ summarized that in 312 reported cases of small intestinal perforations, none was caused by a fall on stairs, and in 677 reported cases of falls on stairs, none resulted in intraabdominal injuries. While there is undoubtedly overlap in the intra-abdominal injury patterns of accidental and inflicted
trauma in the pediatric patient, NAT should be seriously considered in patients less than 4 years of age, in those with a pancreatic injury or hollow viscus injury, and in cases where the stated mechanism of injury is discordant with the severity of injuries.

Assessment by clinicians of the injured child in the emergency department requires a stepwise approach that primarily evaluates for immediately life-threatening injuries and then secondarily searches for less severe injuries. Upon initial presentation at an experienced trauma center, if intra-abdominal injury is suspected, focused assessment by sonography for trauma (FAST) may be utilized as an initial diagnostic tool for detection of hemoperitoneum.^20,21 The technique simply involves a rapid assessment of the four quadrants of the abdomen and the paracolic gutters by ultrasound to identify free fluid (Fig. 18.3). The use of FAST is controversial in children, and a thorough meta-analysis including review of 25 studies and 3,838 children published by Holmes et al.²² indicates that abdominal ultrasonography in the pediatric population performs modestly in detecting hemoperitoneum or intra-abdominal injury, with the following test characteristics: sensitivity of 80% (95% confidence interval [CI] 76% to 84%); specificity of 96% (95% CI 95% to 97%), positive likelihood ratio of 22.9 (95% CI 17.2 to 30.5), and negative likelihood ratio of 0.2 (95% CI 0.16 to 0.25). The high positive likelihood ratio supports prompt cross-sectional imaging of a hemodynamically stable child with suspected abdominal trauma and intraperitoneal fluid seen on FAST. However, a negative ultrasound is not sufficient to definitively rule out the presence of intra-abdominal injury, and therefore, if the pretest probability of injury is high enough, it is reasonable to utilize contrast-enhanced abdominal CT as the initial diagnostic imaging test. Clinicians may consider sonography as the sole diagnostic test in a limited cohort of trauma patients who have a low risk of intra-abdominal injury.