Findings: Free gas (most important finding). In the absence of known benign cause, diagnosis is perforated viscus. Tract of gas from distal stomach is visualized posteriorly, which was the source.

Objectives:

• To identify pneumoperitoneum and have a basic differential diagnosis

• To practice identifying the source of pneumoperitoneum

Protocolling:

• Contrast enhanced CT

Key points:

• Anatomy:

  • Review small and large bowel anatomy

• Differential diagnosis:

  • Perforated viscus (PUD, ischemic bowel, appendicitis, diverticulitis, etc)

  • Post-operative

  • Peritoneal dialysis

• If perforated viscus is suspected, patient will go to OR.

• Identifying the source of free gas:

  • Amount and location of gas collections (assess for intra and retroperitoneal gas)

  • Look for:

    • Localized air bubbles

    • Focal bowel wall thickening

    • Bowel wall discontinuity

    • Focal pathology (i.e. appendicitis, diverticulitis, PUD)