Pneumoperitoneum | Video No. 14 | X ray signs

Pneumoperitoneum refers to the presence of air within the peritoneal cavity, typically resulting from a rupture in bowel loops caused by obstruction or other factors. On an erect abdominal X-ray, this condition is identified as radiolucency under the right dome of the diaphragm due to free gas accumulation. Normally, only liver tissue appears below this area on an X-ray; however, in pneumoperitoneum cases, trapped air creates visible changes.

In pneumoperitoneum, air in the peritoneal cavity allows visualization of abdominal structures on an x-ray that are typically not visible. The "football sign" indicates excessive distension due to trapped air, and liver margins become discernible—an unusual finding in normal conditions. Additionally, bowel walls can be seen clearly because the contrast between intraluminal and extraluminal air highlights their borders.

Air accumulation beneath the central tendon of the diaphragm is identified as the cupola sign. When air surrounds both sides of the falciform ligament, outlining it distinctly, this phenomenon is termed as the falciform ligament sign. The liver edge becomes visible due to specific conditions and is referred to as liver edge sign. Additionally, when bowel walls are outlined by internal and external air on both sides, it forms what’s known as Rigler's Sign.

Pseudo-pneumoperitoneum occurs when the descending colon is positioned between the liver and diaphragm, creating an appearance of free gas under the right dome of the diaphragm on X-rays. This phenomenon mimics pneumoperitoneum but does not involve actual free air in the peritoneal cavity.