Pneumoperitoneum |
What are the common causes for pneumoperitoneum?
- Perforated viscus is the primary concern
- Other considerations are:
- Surgery
- Dialysis
- Toxic megacolon
- In females (intercourse, douching, insufflation)
- Pneumatosis intestinalis or coli
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What imaging procedure would you order when you suspect perforated viscus?
- Upright chest x-ray
- Plain films of the abdomen upright to include the diaphragm
- CT scan would also show signs of pneumoperitoneum and the cause, such as bowel perforation.
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How do you recognize pneumoperitineum in plain abdominal radiographs? What are the common imaging findings of air in peritoneum?
- An upright chest x-ray can detect as little as 1 ml of air injected into the peritoneal cavity under the diaphragm.
- A cross-table lateral x-ray with the patient in the left lateral position (left lateral decubitus view) can detect 5-10 ml of gas under the lateral abdominal wall.
- In a supine film, air may be seen in the sub-hepatic region.
- A supine film can show a large air collection beneath the abdominal wall that doesn't conform to any bowel loop.
- Free air can be seen under the central tendon of the diaphragm.
- Falciform ligament can be visualized in pediatric cases.
- (Rigler's sign).: Both walls of the bowel (Double wall sign) seen due to air within and outside the bowel.
- Massive air gives rise to a "Football' sign in pediatric cases.
Bowel perforation / Pneumoperitoneum
Findings:
- Upright film of abdomen demonstrates air under the right hemidiaphragm (white arrow).
- Arrowheads point to multiple bowel loops with air fluid levels.
- Black arrow points to air fluid level in stomach.
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Bowel perforation / Pneumoperitoneum
Findings:
- White arrow points to diaphragm.
- Black arrow points to subdiaphragmatic air.
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Large Pneumoperitoneum
Findings:
- Arrow points to free air central tendon
- Arrow heads pointing to free air
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Pneumoperitoneum
Findings:
- Massive - Football sign
- Air collects under the anterior aspect of peritoneal cavity
- L: Liver
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Appearance of Free Air in CT Abdomen:
Bowel perforation / Pneumoperitoneum
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- White arrow points to diaphragm.
- Arrowheads points to subdiaphragmatic air.
- Central arrowhead points to free air under the central tendon of the diaphragm.
- L: Air in the lungs.
- In lung window, lung markings are seen separating the lungs from free air.
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Pneumoperitoneum
- Arrowheads point to free air.
- Arrows points to collection of fluid around bowel loops.
- Black arrows point to pericolonic fascial infiltration consistent with abscess.
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