Implications of Isolated Free Fluid in Pediatric Trauma Patients

The imaging finding of isolated free fluid in pediatric trauma patients is of unclear clinical significance. The study's purpose was to identify discriminatory features of isolated free fluid to determine which characteristics justify conservative management versus those concerning for radiologically occult injury, using a retrospective cohort study. We hypothesize that if free intraabdominal fluid is identified as an isolated finding in pediatric trauma patients by CT evaluation, then higher volume of fluid, fluid in more anatomic spaces, and more complex fluid may indicate a higher likelihood of an injury requiring surgical intervention.

A retrospective cohort study was performed on 100 pediatric trauma patients with CT evidence of isolated free fluid between 2007 through 2020. Philips Tumor Tracker was used to determine fluid volume and density. Patients were divided into two groups: those without intraoperative evidence of injury (n = 93) and those with intraoperative evidence of injury (n = 7). Fluid volume, density, and pockets of fluid were compared between groups.

Fluid volume, density, and number of fluid pockets were all statistically significantly different (p < 0.05). Average fluid volume was 4 ± 6 mL in non-injured patients and 31 ± 29 mL in injured patients. The highest density fluid collection was 13 ± 10 HU in non-injured patients and 40 ± 12 HU in injured patients. Specifically, a cutoff value of 5 mL had 100 % negative predictive value. 96 % of non-injured patients had free fluid in only one location, while 85 % of injured patients had fluid in multiple locations. All of the injured patients had fluid pockets other than or in addition to the pelvis. Additionally, fluid in the central mesentery was found only in injured patients.

Small volume, simple fluid in the pelvis of pediatric male or premenstrual female patients should not raise concern for underlying injury, even in a trauma setting.

Retrospective cohort study.

Level III.