Pneumoperitoneum

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
Causes include post laparotomy, dissection of air from a pneumomediastinum into the peritoneum, or rupture of a hollow viscus. The most common organ to perforate in a newborn (aside from perforations caused by necrotizing enterocolitis) is spontaneous perforation of the stomach. In older children the most common causes of pneumoperitoneum are a perforated peptic ulcer or Meckel diverticulum.

Pathology:
Not applicable

Imaging Findings:
Best seen on an upright, left lateral decubitus, or cross table lateral view of the abdomen. Signs of pneumopertioneum include:

Football sign - the falciform ligament is surrounded by air and is visible as the "laces" of the football.

Rigler's sign - gas is seen on both sides of the bowel wall.

Telltale triangle - free air accumulating in between two loops of bowel and the abdominal wall

Gas outlining the urachus or folds of the umbilical arteries.

Gas outlining the liver, spleen or gallbladder.

Diffuse lucency of the abdomen on a supine film.

DDX:

• Not applicable

References:
See References Chapter.

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