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Bowel Ischemia


KEY FACTS

Terminology

  • Small bowel (SB) ischemia resulting from mesenteric arterial or venous narrowing or occlusion, leading to inadequate supply of nutrients and oxygen

Imaging

  • Best imaging tool

    • CT angiography; multiplanar reformations; water for oral contrast

    • Catheter angiography for confirmation & treatment

  • Imaging findings vary, based on etiology and acuity of ischemic injury

  • Acute arterial thrombosis or embolus

    • Little SB wall thickening, mesenteric edema, or ascites

    • Lack of bowel mucosal enhancement due to compromised arterial flow

    • CT signs of embolic ischemic injury to other organs

  • Chronic arterial occlusive disease

    • Narrowing or occlusion of SMA with collateral vessels

  • Mesenteric venous thrombosis

    • Fluid-distended SB with thick walls

    • Infiltrated mesentery and ascites

    • Occurs in prothrombotic (hypercoagulable) disorders

  • Pneumatosis intestinalis and portal venous gas

    • Not sensitive nor specific for bowel ischemia

    • Branching gas extending to periphery of liver

  • Nonocclusive bowel ischemia

    • Common etiologies: Closed-loop SB obstruction; cocaine or methamphetamine use; hypotensive episode; vasculitis

  • Multiplanar, multiphasic CECT is best imaging tool

    • Can generate CT angiogram; makes arterial or venous occlusion more apparent and quantifiable

    • Shows etiology of nonocclusive ischemia (e.g., closed-loop SB obstruction)

  • Catheter angiography

    • Diagnostic confirmation and treatment of arterial occlusive disease

Diagnostic Checklist

  • Diagnosis of bowel ischemia demands correlation of clinical, laboratory, and imaging findings

Graphic shows a dilated small bowel (SB)
with thickened wall, ascites
, and edematous mesentery
, all findings seen with occlusion of the superior mesenteric vein.

Axial CECT in an elderly woman with abdominal pain demonstrates dilated SB with pneumatosis
. Portal venous gas was also present on other sections (not shown). No enhancement of SB mucosa is seen, indicating arterial occlusion as the etiology. Infarcted bowel was confirmed at surgery, and the patient died.

In this elderly man complaining of severe abdominal pain, axial CT section, viewed at "lung windows," shows portal vein gas
as a branching air density extending to the periphery of the liver.

In the same patient, CT shows pneumatosis and gas in the wall of the colon
and SB. These findings, in concert with the symptoms and laboratory evidence of lactic acidosis, are diagnostic of bowel ischemia.

TERMINOLOGY

Synonyms

  • Acute mesenteric ischemia

Definitions

  • Small bowel (SB) ischemia resulting from mesenteric arterial or venous narrowing or occlusion, leading to inadequate supply of nutrients and oxygen

IMAGING

General Features

  • Best diagnostic clue

    • Pneumatosis (SB wall gas) ± portal vein gas

      • –

        This is late sign; neither sensitive nor specific for bowel infarction

    • Imaging findings vary, based on etiology and acuity of ischemic injury

Radiographic Findings

  • Radiography

    • Dilated bowel with air-fluid levels; ileus pattern

    • Thickening of valvulae conniventes

    • Linear distribution of gas (pneumatosis intestinalis)

Fluoroscopic Findings

  • Barium studies

    • Thickening of valvulae conniventes (transverse SB folds)

    • Thumbprinting pattern: Intramural accumulation of blood distending submucosa → focally rounded SB folds, especially along mesenteric border

    • Stack of coins pattern: Enlarged, smooth, straight, parallel folds perpendicular to longitudinal axis of SB (submucosal edema)

    • Strictures often seen with proximal bowel dilation (subacute or chronic finding)

    • Mottled, frothy, bubbly, or linear collections of gas in bowel wall (pneumatosis intestinalis)

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