What are the major causes of pneumoperitoneum?
Pneumoperitoneum (i.e., gas in the peritoneal cavity) is most often due to bowel perforation involving the intraperitoneal portions of bowel (i.e., the stomach, first portion of the duodenum, jejunum, ileum, cecum, transverse colon, sigmoid colon, and upper rectum) and recent abdominopelvic surgery. It is less commonly due to peritoneal infection, peritoneal dialysis, gastrostomy tube placement, rupture of pneumatosis cystoides intestinalis, rapid decompression after diving, extension of gas from the thorax (such as during mechanical ventilation), and extension of gas through the female genital tract (such as during pelvic physical examination). Very low attenuation and very low signal intensity gas within the peritoneal cavity is seen on CT and MR images, respectively
