Figure 1: Click on image to enlarge



Various radiological signs have been attributed to the appearance of pneumoperitoneum on the plain abdominal radiograph.  These include:


The falciform ligament sign

Rigler’s sign (Double bowel wall sign)

Triangles of air

The continuous diaphragm sign

The ‘football’ sign


The football sign, which is seen on supine abdominal radiographs, refers to a large oval radiolucency in the shape of an American style football (A rugby ball to the English!). The long axis of the “football” runs cephalo-caudad, with the blunted ends defined by the diaphragm and pelvic floor.


The oval radiolucency seen in the ‘football sign’ represents a massive pneumoperitoneum, which distends the peritoneal cavity. In the supine position, free air collects anterior to the abdominal viscera, producing a sharp interface with the parietal peritoneum and thereby creating the football shaped outline. The pneumoperitoneum may outline the falciform ligament (as in this case), which is seen as a faint linear opacity situated longitudinally within the right upper abdomen (from the right upper quadrant to the umbilical area).


The ‘football sign’ almost exclusively occurs in infants.  It is usually due to either spontaneous or iatrogenic perforation

Causes of pneumoperitoneum in neonates include;  necrotising enterocolitis (NEC), gastric perforation, bowel obstruction (For example from; malrotation with midgut volvulus, Hirschsprung disease or atresia), and sources of inflammation such as gastric or duodenal ulcers.



Image and text contributed and prepared by

Dr Ian Bickle, Department of Radiology, RIPAS Hospital, Brunei Darussalam.

All images are copyrighted and property of RIPAS Hospital.