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Splenic Trauma in Children
Abdominal injury occurs in approximately 10% to 15% of pediatric trauma patients, with the spleen being the most commonly injured intraabdominal organ, accounting for a significant proportion of the management expenses incurred with blunt traumatic injuries. Historically the initial management of splenic injury was emergent splenectomy. However, as the immunologic importance of the spleen became evident with the recognition of postsplenectomy sepsis, spleen-preserving strategies were implemented, particularly in children. In 1952 King and Shumacher first reported two deaths among five infants who developed severe sepsis following splenectomy for hereditary spherocytosis. The spleen is now known to play important immune functions, including the eradication of such encapsulated bacteria as Streptococcus pneumoniae , Neisseria meningitidis , and Haemophilus influenzae type B. The rate of postsplenectomy sepsis in children less than 5 years of age is greater than 10%, compared with less than 1% in adults, with a reported life-long risk greater than 85 times that of the normal population and a mortality rate approaching 70%. Thus, following splenectomy, patients must take penicillin prophylaxis for varying periods of time to decrease the risk of developing postsplenectomy sepsis. In addition, splenectomy increases the risks of short-term hematologic complications and long-term cardiovascular complications. Comparisons of “quality-adjusted life expectancy” after blunt splenic trauma for the treatment options of observation, splenorrhaphy, and splenectomy have shown a decreased life expectancy for patients undergoing splenectomy. Long-term cost savings from splenic preservation could include prescription drug costs both from prophylactic antibiotics and vaccinations, as well as decrease in hospitalizations associated with postsplenectomy infections.
In light of these findings and the observation that bleeding from splenic injuries had often ceased by the time of laparotomy, the treatment of children with blunt splenic injuries evolved from emergent splenectomy to splenic preservation. Upadhyaya and Simpson first described in 1968 selective nonoperative management (NOM) of splenic injuries in children sustaining blunt trauma. Since this initial description, multiple guidelines and protocols have been described, all with success rates greater than 90%. Thus NOM is now the standard of care for blunt splenic injuries in children. Interestingly, the success of NOM in children prompted the application of NOM to blunt splenic injuries in adult trauma patients, although the success rate has been lower.
Spleen Anatomy and Physiology
The unique segmental blood supply of the spleen readily permits repair and resection of the injured spleen. Vascular anatomy usually consists of superior and inferior segments in 84% compared with superior, middle, and inferior segments in 16% ( Fig. 140.1 ). These segments are separated by avascular planes that pass obliquely to the longitudinal axis of the spleen and often do not traverse the full thickness of the spleen from the parietal to visceral surfaces. Intrasplenic vessels are lobar, segmented, and generally without intersegmental communication. Dixon et al. divided the spleen into three-dimensional zones (hilar, intermediate, and peripheral), with each zone requiring a specific technique for hemostasis. Bleeding from the peripheral zone may be managed with topical agents, whereas ligation is recommended for the trabecular and segmental vessels in the intermediate and hilar zones ( Fig. 140.2 ).
Compared with the adult spleen, the splenic capsule in children is relatively thicker and contains abundant myoepithelial cells that favor hemostatic control of hemorrhage. The more efficient contraction and retraction of splenic arterioles, as well as the lack of atherosclerosis, confer greater vascular compliance, further improving contraction leading to more effective hemostasis. Inferior rib fractures are commonly associated with splenic injuries in adults, with the broken rib often penetrating the splenic capsule. In contrast, rib fractures are rarely seen in children because their ribs have greater elasticity, allowing the ribs to recoil rather than fracture, thereby reducing the direct force to the spleen and the risk of penetrating the splenic capsule.
Evaluation of Splenic Trauma in the Child
Evaluation of the pediatric trauma patient proceeds systematically as outlined by Advanced Trauma Life Support (ATLS), prioritizing the assessment and management of the airway, breathing, and circulation. Sequential assessment and maintenance of airway patency, adequacy of gas exchange, and perfusion are the priorities of resuscitation, preventing and/or correcting hypoxemia due to inadequate oxygen delivery.
Many children with abdominal injuries have either equivocal or absent physical findings, with a reported overall accuracy of initial physical examination varying from 16% to 45%. Thus reliance on physical examination alone is an inadequate evaluation of the child with potential abdominal injury. Diagnostic adjuncts in the evaluation of the abdomen include focused assessment sonography in trauma (FAST) and computed tomography (CT). However, if the patient is hemodynamically unstable from an intraabdominal source, the child undergoes immediate surgical exploration. If the patient responds to resuscitation, more definitive diagnostic imaging can then be performed.
Ultrasound has many advantages, including portability, immediate availability, lack of ionizing radiation, noninvasiveness, and low cost. During the FAST exam, the operator focuses on identifying free fluid in the subxiphoid region (heart), left flank (spleen), right upper quadrant and Morrison pouch (liver), and pelvis and pouch of Douglas. Although fast, FAST does not reliably identify the injured organ or the quality of the identified free fluid (blood, succus, urine) and can miss solid organ injuries not associated with free fluid. Thus ultrasound may miss intraparenchymal injuries or downgrade injuries. In addition, the quality of the exam is dependent upon the operator in both performing and interpreting the exam. In a systematic review and meta-analysis, abdominal ultrasound was found to have modest sensitivity (66%) in the detection of hemoperitoneum in children sustaining blunt trauma but low specificity. Moreover, a negative ultrasound examination has questionable utility as the sole diagnostic test to rule out intraabdominal injuries in the pediatric trauma patient. Rather, the utility of FAST exam seems to be in the evaluation of the hemodynamically unstable patient to aid in the identification of areas of injury and help to prioritize interventions.
CT of the abdomen and pelvis is the current standard of care for the evaluation of the peritoneal cavity and retroperitoneum. Intravenous contrast provides maximal information regarding organ perfusion, presence of free intraperitoneal fluid, and characteristics of the bowel. Enteral contrast is generally not required in the acute trauma setting and can lead to aspiration. There is a reported correlation between the severity of the solid organ injury and the likelihood and volume of associated free fluid. The most common location of free fluid regardless of the site of injury (spleen or liver) is the pelvis. Free fluid is more common in splenic injury (82%) compared with liver injury (69%).
Due to concern regarding the long-term risk of radiation exposure, the use of any ionizing radiation in children has been particularly scrutinized and limited as much as possible. Although CT is an essential imaging modality, there is an obligatory exposure to ionizing radiation that has been demonstrated to increase the risk of cancer, particularly in children. Compared with adults, the cancer risk from radiation exposure in children is not insignificant and may be more pronounced due to a number of factors. The same amount of radiation exposure results in a relatively higher dose to children due to their smaller cross-sectional area, compared with adults. Tissues and organs that are growing and developing are more sensitive to radiation effects than mature tissue, and the oncologic effect of radiation may have a longer latent period. In addition, an infant or child has a longer life expectancy during which to manifest the potential oncologic effects of radiation compared with the adult. Thus, to decrease radiation exposure, radiologists use radiation doses that are as low as reasonably achievable (ALARA), which means that no more radiation should be used than is required to achieve the necessary diagnostic information and to perform these studies only when they are necessary.
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