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 football. The long axis of the "football" runs cephalocaudad, and the blunted ends are defined by the diaphragm and pelvic floor. The oval radiolucency seen in the football sign represents 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 outline. The pneumoperitoneum may outline the falciform ligament, which is seen as a faint linear opacity situated longitudinally within the right upper abdomen.
Reference- Radiology 2004;231:81-82
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