Pediatric Pneumoperitoneum

Etiology:
— Barotrauma (pneumothorax or pneumomediastinum dissecting into abdomen)
— Nasogastric tube perforating stomach
— Indomethacin used to close patent ductus arteriosus causing gastric ulcer
— Necrotizing enterocolitis
— Obstruction
— Blunt abdominal trauma
Imaging CXR upright: Air beneath diaphragm
Imaging AXR upright: Air beneath diaphragm
Imaging AXR left lateral decubitus: Air above the liver (air between abdominal wall and liver)
Imaging AXR cross-table lateral:
— For small amounts of free air see tell-tale triangle sign of triangles of air between bowel loops
— For large amounts of free air see air superiorly between abdominal wall and viscera
Imaging AXR supine:
— Overall increased lucency of abdomen
— American football sign of falciform ligament outlined by air
— Inverted Y of umbilical artery ligaments
— Rigler’s sign (see air outlining both sides of bowel wall)
Imaging US: Dirty shadowing just beneath peritoneum
Note:
— Neonates with bowel perforation have an inflamed abdomen and pneumoperitoneum may be loculated and not be classically seen on upright or decubitus or cross-table lateral views and pneumoperitoneum may appear as fixed air collection that does not appear to conform to bowel
— In such cases US showing complex free fluid may assist in making the diagnosis of bowel perforation keeping in mind the differential diagnosis of complex free fluid is bowel perforation or infection or hemorrhage
DDX:
Complications:
Treatment: Surgical
Clinical:

Radiology Cases of Pneumoperitoneum

Radiology Cases of Pneumoperitoneum on Upright AXR

CXR of pneumoperitoneum — Upright CXR shows free air beneath the diaphragm.

Radiology Cases of Pneumoperitoneum on Decubitus AXR

AXR of pneumoperitoneum — Left lateral decubitus AXR shows free air between the right abdominal wall and the liver.

AXR of pneumoperitoneum — Right lateral decubitus radiograph of the abdomen shows a large amount of free air within the abdomen.

AXR and gastrojejunostomy tube injection of pneumoperitoneum due to malposition of the gastrojejunostomy tube outside of the bowel — Supine (above left) and left lateral decubitus (above right) AXR show no evidence of air between the abdominal wall and the liver but on the decubitus view several concerning air bubbles project over the liver and appear extra-lumenal. The gastrojejunostomy tube was exchanged for a gastrostomy tube and AP image from a gastrostomy tube injection with water soluble contrast (below) shows contrast extravasating inferiorly out of the duodenum at the junction of the second and third parts of the duodenum.

AXR of pneumoperitoneum due gastrostomy tube malposition causing gastric perforation — Supine AXR (left) shows a gastrostomy tube projecting appropriately over the stomach with a triangular lucency superior to the stomach. Left lateral decubitus AXR (above right) again shows the triangular lucency superior to the stomach but does not show air between the abdominal wall and liver. Cross-lateral AXR (below right) shows air between the anterior abdominal wall and liver.

AXR of pneumoperitoneum due to malposition of gastrojejunostomy tube outside of bowel — Supine AXR (above) shows the tip of the gastrojejunostomy tube extending deep into the pelvis. Left lateral decubitus AXR (below) shows air between the abdominal wall and the liver.

Radiology Cases of Pneumoperitoneum on Cross-Table Lateral AXR

AXR of pneumoperitoneum — Cross-table lateral AXR shows a large amount of free air superiorly in the abdomen outlining some of the bowel loops and compressing the rest posteriorly.

AXR of pneumoperitoneum in a patient with respiratory distress syndrome — AXR cross-table lateral shows a distended abdomen with a huge amount of air between the anterior abdominal wall and the abdominal organs.

Radiology Cases of Pneumoperitoneum on Supine AXR

AXR of pneumoperitoneum in a patient with respiratory distress syndrome — CXR AP shows a bubbly branching appearance to the right lower lobe and overall increased lucency throughout the entire abdomen.

AXR of pneumoperitoneum — Supine AXR shows increased lucency in the upper abdomen without clear demonstration of the football sign of the falciform ligament being outlined by free air.

AXR of pneumoperitoneum — Supine AXR shows increased lucency in the upper abdomen with clear demonstration of the 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).

Air enema of intussusception reduction — AXR scout image (above left) shows a non-obstructive bowel gas pattern. AP image from the start of an air enema begun after manual reduction of the mass into the rectum (above right), shows the tip of the rectal catheter in contact with the mass in the rectum. AP image from later in the study (below left) shows the mass now in the transverse colon near the splenic flexure. Despite multiple attempts the intussusception could not be reduced further and the exam was ended when air was seen outlining the liver and both sides of the wall of the small bowel (Rigler’s sign)(below right). In the operating room the intussusception was reduced manually and a site of perforation could not be found.

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.

AXR of bowel perforation — AXR AP (above) shows a large oval lucency in the midline of the upper abdomen. Cross table lateral AXR (below) shows a large amount of air between the abdominal wall and the liver. There is also air outlining both sides of the bowel wall of a loop of bowel (Rigler’s sign).

AXR of gastric perforation from nasogastric tube placement — Supine AXR (left) shows a large amount of air within the abdomen and air outlining both sides of bowel wall (Rigler’s sign) in the right lower quadrant. Supine AXR taken later after pulling back of the nasogastric tube out of the stomach shows visualization of the falciform ligament over the spine (American football sign)

AXR of gastric perforation from nasogastric tube placement — Supine AXR (above) shows increased lucency throughout the central abdomen and left lateral decubitus AXR (below) shows air between the abdominal wall and the liver. On both views the tip of the nasogastric tube projects inferior to the gas-filled stomach.

AXR of gastric perforation from nasogastric tube placement — Supine and left lateral decubitus AXR (left) show a nasogastric tube with its tip deep in the pelvis without evidence of free air. Supine AXR taken after pulling the nasogastric tube back into the stomach (above right) shows increased lucency throughout the central abdomen and left lateral decubitus AXR taken at same time (below right) shows air between the abdominal wall and the liver.

Radiology Cases of Pneumoperitoneum on Supine CXR

CXR and AXR of pneumoperitoneum — CXR AP (above) shows increased lucency in the upper abdomen. Left lateral decubitus AXR (below) shows a large amount of free air between the abdominal wall and the liver.

Radiology Cases of Pneumoperitoneum and Pneumothorax

CT of congenital diaphragmatic hernia — CXR (left) shows massive pneumoperitoneum and right pneumothorax which outlines a mass in the lower right chest which is causing mediastinal shift to the left. Coronal CT with contrast of the chest (above right) shows liver herniating through a lateral defect in the diaphragm into the lower right chest and lying above the right diaphragm (below right).