Ultrasonographic Evaluation of Physiologic Free Intraperitoneal Fluid in Healthy Children: A Prospective Observational Study

Objectives: The detection of intraperitoneal free fluid (FF) is an important finding in the sonographic evaluation of the pediatric abdomen, especially in the context of blunt abdominal trauma. One specific challenge is differentiating physiologic from pathologic FF. The purpose of this study was to determine with ultrasound the prevalence, location, and volume of intraperitoneal FF in healthy pediatric patients and its relation to pubertal status and gender.

Methods: Healthy children between the ages of 1 and 17 years who presented to the emergency department with non-abdominal complaints were evaluated for physiologic intra-abdominal fluid. Point-of-Care Ultrasound (POCUS) was performed, utilizing the Focused Assessment with Sonography in Trauma (FAST) examination.

Results: A total of 325 pediatric patients were analyzed. Intraperitoneal FF was found in 52 children (16.0%, 95% CI: 12.0-20.0%). The pelvis was the only region where FF was located. The prevalence of FF was nearly equivalent between male and female children (15.4% vs 16.7%, P = .76). There was a higher prevalence of FF identified in the prepubertal subgroup compared to the pubertal group (20.0% vs 11.3%, P = .03). Seventy-seven percent of children with FF had a fluid volume of less than 1 mL.

Conclusions: Physiologic FF of less than 1 mL within the pelvis is a common finding in the pediatric population. There was no difference in the rate of FF identified by gender, but there was a higher prevalence of FF among prepubertal children.