Nominal free air in the left inguinal fossa due to perforation of the sigmoid colon in a case of blunt abdominal trauma: CT diagnosis.

We present a case of perforation of the sigmoid colon due to blunt abdominal trauma. Computed tomography showed nominal free air in the inguinal fossa. The distribution of free air may be a clue to the site of an injured intestine. Early detection of intestinal injury is difficult, but repeated computed tomography after several hours may reveal increased free air.