Small Bowel Perforation

  • Etiology: placement of a gastrojejunostomy tube, use of indomethacin to close a patent ductus arteriosus, bowel atresia, ischemic necrosis, blunt trauma
  • AXR left lateral decubitus: air above the liver (air between abdominal wall and liver)
  • AXR cross-table lateral: for small amounts of free air see tell-tale triangle sign of air between bowel loops, for large amounts of free air see air superiorly between abdominal wall and viscera
  • AXR supine: overall increased lucency of abdomen, American football sign of falciform ligament, inverted Y of umbilical artery ligaments, Rigler’s sign (see air outlining both sides of bowel wall)
  • Note: in inflamed abdomen (due to perforation), pneumoperitoneum may be loculated and not be classically seen on upright / decubitus / cross-table lateral views, may appear as fixed air collection that does not appear to conform to bowel

Cases of Small Bowel Perforation

AXR of pneumoperitoneum
Supine AXR shows increased lucency in the upper abdomen without clear demonstration of the American football sign of the falciform ligament being outlined by free air.
AXR of pneumoperitoneum
Supine AXR obtained during an intussusception reduction shows air outlining both the inner and outer walls of the small bowel (Rigler’s sign).
AXR of pneumoperitoneum
Supine (left) and upright (right) AXR show a central fixed air collection that does not appear to conform to bowel and does not demonstrate any of the classic signs of free air.
AXR of esophageal perforation from nasogastric tube placement
Supine AXR (above) shows increased lucency in the upper abdomen. The cross-table lateral AXR (below) shows air between the anterior abdominal wall and the bowel. The nasogastric tube follows a very straight course and does not curve towards the stomach. Note on both views that the tip of the nasogastric tube does not project over the stomach. US performed subsequently showed the tip of the nasogastric tube was in the retroperitoneum and not in the stomach.