Traumatic pneumoperitoneum following combined abdominal and thoracic injury.

Pneumoperitoneum following blunt abdominal trauma in the absence of other signs of severe intraabdominal injury is a rare finding. Although the vast majority of all cases of pneumoperitoneum are due to a ruptured intraabdominal hollow viscus, free abdominal air may result from significant barotrauma to the thorax. This type of secondary pneumoperitoneum can occur in the absence of chest x-ray evidence of a pneumothorax or pneumomediastinum. The complications associated with a missed visceral injury warrant an exploratory laparotomy, even if an extraabdominal source for the pneumoperitoneum is suspected.