Pneumoperitoneum – Rigler’s sign – PFA

Pneumoperitoneum. An erect CXR is much more sensitive when looking for free intraperitoneal gas, however we occasionally encounter it on abdominal xrays and you should be aware of its potential appearances. This example, in a patient who developed severe pain following a colonoscopy, shows the classic ‘Rigler’s sign’, in which gas is visible on both sides of the bowel wall. The sign is present at several sites in this case, some of which are indicated by the arrows.

Potential causes of pneumoperitoneum include:

• perforated hollow viscus – most commonly due to diverticulitis or peptic ulcer disease; other, less frequent sources include appendicitis, bowel obstruction, bowel ischaemia, inflammatory bowel disease and iatrogenic (e.g. colonoscopy, ERCP)
• recent laparotomy or laparoscopy
• peritoneal dialysis
• extension into abdomen from the chest (pneumomediastinum, pneumothorax)