Pneumoperitoneum seen on X-ray with the patient lying on his left side.
Pneumoperitoneum is the presence of air or gas in the abdominal (peritoneal) cavity. It is often seen on X-ray, but small amounts are often missed, and CT is nowadays regarded as a criterion standard in the assessment of a pneumoperitoneum. CT can visualize quantities as small as 5 cm³ of air or gas. The most common cause is a perforated abdominal viscus, generally a perforated peptic ulcer, although any part of the bowel may perforate from a benign ulcer, tumor or abdominal trauma. A perforated appendix seldom causes a pneumoperitoneum.
In the mid-twentieth century, an "artificial" pneumoperitoneum was sometimes intentionally administered as a treatment for a hiatal hernia. This was achieved by insufflating the abdomen with carbon dioxide. The practice is currently used by surgical teams in order to perform laparoscopic surgery.