CT scan-detected pneumoperitoneum: an unreliable predictor of intra-abdominal injury in blunt trauma.

ABSTRACT

INTRODUCTION: Free intra-peritoneal air in blunt trauma is a classic sign associated with hollow viscus injury, traditionally mandating laparotomy. In blunt abdominal trauma, the CT scan has become the diagnostic modality of choice. The increased sensitivity of CT scans may lead to detection of free intra-peritoneal air that is not clinically significant. OBJECTIVE: To characterize conditions and findings that allow for the safe observation of blunt trauma patients with free air and to propose a patient management algorithm to decrease rates of non-therapeutic laparotomy. DESIGN: A retrospective review of 5877 blunt trauma patients who had an abdominal CT scan upon admission to our hospital from 2003 to 2011. A secondary CT review was performed by a single radiologist to further characterize the CT findings in the 74 patients with free air reported on initial scan. Management and hospital course were reviewed in these patients. RESULTS: Of the 74 patients with intra-abdominal free air, 36 patients with a benign clinical picture were observed and 38 patients underwent urgent exploratory laparotomy. Eleven patients received a non-therapeutic laparotomy. The majority (61%) of patients, 45 of 74, had free air and no significant injury suggesting the presence of benign free air. Patients who had intra-abdominal injury also typically had other clinical or radiologic signs of injury. Findings that were highly predictive of intra-abdominal injury in the setting of free air were free fluid (P<0.001), radiographic signs of bowel trauma (P<0.001) as well as clinical and/or radiographic seatbelt sign (P=0.004). CONCLUSIONS: CT scans may detect free air that is not always clinically significant. Free fluid, seatbelt sign or radiographic signs of bowel trauma in the presence of pneumoperitoneum is highly predictive of injury and these patients should be explored. Based on the results of our study, we created an algorithm to aid in identifying those patients with intra-abdominal free air who may be observed safely.