The FAST Exam in Children

FAST is a helpful adjunct to the initial evaluation of adult trauma patients. Unfortunately, due to small numbers the usefulness is not as clear in children. In part, this is due to the fact that many children (particularly small children < 10 years old) have a small amount of fluid in the abdomen at baseline. This makes interpreting a FAST exam after trauma more difficult.

Despite this, use of FAST in children is widespread. A survey of 124 US trauma hospitals in 2007 showed an interesting pattern of ultrasound usage. In adult-only institutions 96% use FAST, and at hospitals that see both adults and kids, 85% use it. Most of these centers that use FAST have no lower age limit, and the physician most commonly performing the exam was a surgeon. However, only 15% of children’s hospitals do FAST exams, and they were usually done by nonsurgeons! The reasons for this are not clear. It appears that the pediatric surgeons have not embraced this technology as much as their adult counterparts.

What about that confusing bit of fluid found in kids? Several groups have looked at this (retrospectively). Fluid in the pelvis alone appears to be okay, but fluid anywhere else is a good predictor of solid organ injury. Fluid seen outside the pelvis had a 90% sensitivity and 97% specificity for injury, and positive and negative predictive values were 87% and 97% respectively.

Bottom line: FAST exam is useful in pediatric victims of blunt abdominal trauma. Fluid in the pelvis alone is normal in most children, but fluid seen anywhere else indicates a high probability of solid organ injury.


  1. Use of focused abdominal sonography for trauma at pediatric and adult trauma centers: a survey. J Pediatric Surgery 44:1746-1749, 2009.
  2. Minimal pelvic fluid in blunt abdominal trauma in children: the significance of this sonographic finding. J Pediatric Surgery 36(9):1387-1389, 2001.
  3. Clinical importance of ultrasonographic pelvic fluid in pediatric patients with blunt abdominal trauma. Ulus Travma Acil Cerrahi Derg 16(2):155-159, 2010.
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