Objective: To clarify the usefulness of ultrasonography (US) as a diagnostic instrument for intraperitoneal free air (IPFA), which is thought to be useful in the fields of emergency medicine and traumatology.
Design: Prospective observational study.
Setting: Tertiary critical care and emergency center.
Patients: A total of 484 patients with severe chest-abdominal-pelvic blunt trauma or, in the absence of such trauma, severe acute abdominal pain were examined using US to detect IPFA. The exclusion criteria consisted of hemorrhagic shock with massive intraperitoneal fluid, penetrating or open abdominal trauma, and transfer to our center when general surgeons were absent.
Main outcome measures: The primary outcome measure was the sensitivity and specificity of US for the diagnosis of gastrointestinal perforation performed by gastroenterologic or general surgeons with more than 5 years of experience with US. A US diagnosis of IPFA was made if high-echoic spots in the ventral space of the liver were detected. Conclusive diagnosis of gastrointestinal perforation was made based on the operative findings or on radiologic and clinical observation for more than 4 days.
Results: Fifty-four patients were diagnosed as having gastrointestinal perforation. In patients with blunt abdominal trauma, sensitivity for the diagnosis of gastrointestinal perforation by US was 85.7% and specificity was 99.6%; in patients with severe acute abdominal pain, sensitivity was 85.0% and specificity was 100.0%.
Conclusion: Ultrasonography is useful for the diagnosis of IPFA with acute abdominal pain or blunt trauma, except in patients with gastrointestinal perforation without IPFA.