Abdominal Ultrasound in Pediatric Trauma Patients

Abstract

Source: Holmes JF, Gladman A, Chang C. Performance of abdominal ultrasonography in pediatric blunt trauma patients: a meta-analysis. J Pediatr Surg. 2007;42(9)1588–1594; doi:10.1016/j.jpedsurg.2007.04.023According to the CDC Vital Statistics Reports, blunt trauma remains the leading cause of death and disability in children.1Because pathognomic physical examination findings may not be present in many children with blunt abdominal injury, abdominal computed tomographic (CT) scanning has become the standard for identifying intra-abdominal injuries.Increasing awareness of the risk of radiation-induced malignancy has led to the search for alternative diagnostic strategies.2 Consequently, the use of abdominal ultrasound (US) in adult patients with blunt abdominal trauma has increased, and the Focused Assessment with Sonography for Trauma (FAST) exam has become routine in many major trauma centers across the country as a ready means of identifying adult patients with hemoperitoneum.The use of the FAST exam in children with blunt trauma remains controversial. Studies on the use of abdominal US in pediatric trauma patients have yielded conflicting results, and variability in study methods and protocols has led to confusion and disagreement about the usefulness of US in this setting.3The authors, from the University of California at Davis, performed a systematic review of the literature and meta-analysis to assess the test performance of abdominal US in children with blunt traumatic injury. Both prospective and retrospective studies were included if they used abdominal US for the detection of intraperitoneal fluid or intra-abdominal injury in blunt trauma patients less than 18 years of age.Data was then abstracted from the articles and the methodological quality of the articles was graded. Raw data related to US detection of intra-abdominal injury was abstracted from each study and used to generate conservative estimates of sensitivity, specificity, and likelihood ratios. The search yielded more than 1,000 abstracts for initial review. Of those, 25 studies (all cohort studies) involving a total of 3,838 children met all inclusion criteria and were included in the meta-analysis.For identifying children with hemoperitoneum, abdominal US had a sensitivity of 80% and specificity of 96%. When only the most methodologically stringent articles were used (six studies), the combined sensitivity of the FAST exam for identifying children with hemoperitoneum was 66% with a negative likelihood ratio of 0.36 (95% CI, 0.27–0.47). (For a discussion of likelihood ratios, see AAP Grand Rounds Weighing the Evidence, January 2007;17:9.)Sensitivity for detection of all children with intra-abdominal injuries (including those without hemoperitoneum) was even lower at 50%. The authors conclude that ultrasonography has questionable utility as the sole diagnostic test to rule out the presence of intra-abdominal injury in children with blunt trauma.Dr. Cavett has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.FAST examination in children with blunt abdominal trauma has only a modest degree of sensitivity for detection of hemoperitoneum. As stated above, the FAST exam will correctly identify only 66–80% of children with blood in their abdomen following blunt trauma. This 20–34% false negative rate is unacceptably high. This low sensitivity may reflect the difficulty of recognizing the small amounts of fluid in the abdominal cavity sometimes seen in children with intra-abdominal injury.A negative FAST exam cannot rule out an intra-abdominal injury. The greatest limitation of the FAST exam is in the child with intra-abdominal injury with no hemoperitoneum, which can include up to 34% of children with intra-abdominal injury.4–6Addition of solid organ imaging added little to the sensitivity of the exam, and then only when a radiologist interpreted the images. A hemodynamically stable child with a positive FAST exam following blunt abdominal trauma should immediately undergo abdominal CT scan for further evaluation of intra-abdominal injury.It remains challenging for the clinician at the bedside to determine whether abdominal CT remains indicated after FAST. My personal view is that abdominal US can provide helpful reassurance when evaluating the child who is alert and cooperative and has a benign abdomen on clinical examination without other distracting injury, but whose mechanism of trauma is concerning.The study reported here illustrates the utility of the accumulation of case series and the rigorous scientific analysis of such data.