Pneumoperitoneum

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Pneumoperitoneum is air or gas in the abdominal (peritoneal) cavity^[1], 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.^[2].

Causes

The most common cause is a perforated abdominal viscus, generally a perforated ulcer, although any part of the bowel may perforate from a benign ulcer, tumor or trauma. A perforated appendix seldom causes a pneumoperitoneum. A pneumoperitoneum is deliberately created by the surgical team in order to perform laparoscopic surgery. This is achieved by insufflating the abdomen with carbon dioxide.

Perforated peptic ulcer
Bowel obstruction
Ruptured diverticulum
Penetrating trauma
Ruptured inflammatory bowel disease (e.g. megacolon)
Necrotising enterocolitis/Pneumatosis coli
Ischemic bowel
Steroids
After laparotomy
After laparoscopy
Break down of a surgical anastomosis
Bowel injury after endoscopy
Peritoneal dialysis
Vaginal insufflation (air enters via the fallopian tubes, e.g. water-skiing, oral sex)
Colonic or peritoneal infection
From chest (e.g. bronchopleural fistula)

Subphrenic abscess, bowel interposed between diaphragm and liver (Chilaiditi syndrome), and linear atelectasis at the base of the lungs can simulate free air under the diaphragm on a chest x-ray.

Diagnosis

Chest X-ray

Plain film signs of pneumoperitoneum

Rigler’s sign (gas outlining both mucosal and serosal surfaces of bowel wall)
Falciform ligament sign (gas outlining the falciform ligament)
Football sign (gas outlining the peritoneal cavity)

2 days post exploratory laporatomy patient#1 Image courtesy of RadsWiki and copylefted
2 days post exploratory laporatomy patient#1 Image courtesy of RadsWiki and copylefted

Rigler’s sign patient#2 Image courtesy of RadsWiki and copylefted
Rigler’s sign patient#2 Image courtesy of RadsWiki and copylefted
Rigler’s sign patient#2 Image courtesy of RadsWiki and copylefted

patient#3 Image courtesy of RadsWiki and copylefted
patient#3 Image courtesy of RadsWiki and copylefted
patient#3 Image courtesy of RadsWiki and copylefted

Large pneumoperitoneum after indomethicin treatment patient#4 Image courtesy of RadsWiki and copylefted
Large pneumoperitoneum after indomethicin treatment patient#4 Image courtesy of RadsWiki and copylefted

CT

CT can visualize quantities as small as 5 cm³ of air or gas.

Rigler’s sign patient#2 Image courtesy of RadsWiki and copylefted
Rigler’s sign patient#2 Image courtesy of RadsWiki and copylefted

References

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[1] The American Heritage Stedman’s Medical Dictionary. “KMLE American Heritage Medical Dictionary definition of pneumoperitoneum“.

[2] Ali Nawaz Khan. “eMedicine.com: Pneumoperitoneum“.

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