Bowel perforation (summary)

This is a basic article for medical students and other non-radiologists

Bowel perforation is an acute surgical emergency where there is a release of gastric or intestinal contents into the peritoneal space.

Reference article

This is a summary article; read more in our article on bowel perforation.


  • epidemiology
    • depends on the cause
  • presentation
    • history
      • may depend on the location of the perforation
        • severe and generalized abdominal pain (upper)
        • gradual and localized pain (lower)
      • anorexia, nausea and vomiting
    • examination
      • rigid abdomen and generalized tenderness
      • guarding and rebound
      • bowel sounds range from quiet to absent
  • pathophysiology
    • gastric and duodenal ulceration
    • infection (diverticulitis, appendicitis), ischemia and cancer
    • blunt and penetrating trauma
    • ingestion of corrosive materials
    • iatrogenic causes (ERCP, colonoscopy, laparotomy, biopsy)
  • investigation
    • an erect plain radiograph is sensitive for small volumes of free gas
    • a supine abdominal radiograph may show signs of free gas
    • CT with IV contrast is the gold standard investigation
      • free gas and fluid within the peritoneal cavity
  • treatment
    • fluid resuscitation and IV antibiotics
    • surgical intervention is often required to close the perforation
      • bowel resection may be required
    • mortality increases the longer surgical treatment is delayed

Role of imaging

  • confirm free intraperitoneal gas
  • determine the underlying cause
  • if possible, identify the site of perforation

Radiographic features

Plain radiograph
Erect CXR
  • very sensitive to even small amounts of gas within the peritoneal cavity
  • seen as a crescent under the diaphragm
  • summary article: erect chest radiograph
Abdominal X-ray
  • abdominal CT with IV contrast
  • CT is very sensitive for tiny volumes of free gas within the abdomen
  • triangles or bubbles or gas out with the bowel
  • anti dependent - rising to the top of a cavity, e.g. behind the abdominal wall
  • associated fluid within the peritoneal cavity is helpful but non-specific
Finding the cause

CT is also useful to determine the cause of the perforation and is therefore very helpful before surgical intervention.

Where there is more gas than fluid, think lower GI perforation (e.g. sigmoid diverticulitis). Where there is more fluid than gas, upper GI perforation is more likely (e.g. duodenal ulcer).

Medical student radiology curriculum