On CT abdomen of a patient with acute mesenteric ischaemia, which finding indicates transmural bowel infarction and irreversibility?

• A Bowel wall thickening >3 mm with mural stratification
• B Reactive free fluid in the pelvis
• C Closed loop obstruction with beak sign
• D Pneumatosis intestinalis (gas within the bowel wall) ✓

Explanation

Pneumatosis intestinalis — intramural gas within the bowel wall — is a hallmark of transmural ischaemia/infarction on CT, indicating necrosis of the bowel wall and bacterial gas dissection (and sometimes nitrogen off-gassing from disrupted mucosa). Associated portal venous gas (hepatic portal gas on CT) further confirms severe ischaemia. Bowel wall thickening with mural stratification (target sign) indicates subacute or reversible ischaemia with mural oedema. Reactive free fluid alone is non-specific. Closed-loop obstruction indicates mechanical obstruction without necessarily infarction.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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