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Pneumoperitoneum (causes)
AbdomenRadiograph / CT
Free intraperitoneal gas. Most cases reflect a perforated viscus needing surgery; recent surgery and other non-surgical causes must be recognised to avoid unnecessary laparotomy.
Differential
Perforated peptic ulcer
common- •Free gas tracking to a duodenal/gastric wall defect
- •Periduodenal fluid and fat stranding
- •Acute epigastric peritonitis
Perforated diverticulitis / colonic perforation
common- •Sigmoid diverticula with pericolic gas and abscess
- •Faecal-loaded colon; left iliac fossa pain
Recent surgery / laparoscopy
common- •Postoperative context; gas decreasing on serial imaging
- •Expected up to ~1 week post-laparotomy
Bowel perforation from obstruction/ischaemia
less-common- •Dilated bowel or pneumatosis with portal venous gas
- •Wall non-enhancement
Ruptured pneumatosis / diverticulosis (benign)
rare- •Pneumatosis cystoides intestinalis without peritonitis
- •Clinically well despite free gas
Thoracic / iatrogenic tracking
rare- •Barotrauma or recent endoscopy/PEG placement
- •Gas continuity from chest or procedure site
Key discriminators
- •Site of gas and any visible wall defect on CT
- •Recent surgical/procedural history
- •Associated peritonitis vs clinically well
- •Bowel dilatation, pneumatosis or portal venous gas
- •Serial change (postoperative gas resolves)
Work-up / next steps
- 1.Erect chest/lateral decubitus radiograph, then CT to localise perforation
- 2.Correlate with recent surgery/procedures and clinical state
- 3.Urgent surgical review for a perforated viscus
- 4.Conservative management only for confidently benign causes
References
- Radiopaedia: Pneumoperitoneum.
- Pinto A et al. Errors in imaging of pneumoperitoneum. Radiol Med.
Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.